EIC-eRD14 - User contributions [en]

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T19:46:42Z

Greg:

A novel 3-layer spherical lens has been designed for the [https://eic.jlab.org/dirc/index.php/Main_Page Detection of Internally Reflected Cherenkov light (DIRC)] detector system to be used for the EIC. The lens consists of two layers of fused silica sandwiching a thin layer of [https://refractiveindex.info/?shelf=glass&book=SCHOTT-LaK&page=N-LAK7 lanthanum crown glass NLaK33]. The figure below shows two photos of a prototype lens built for testing purposes as well as the dimensions of the lens. Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of the prototype lens and verify the shape and position.

[[File:3CS_Schematic.png | thumbnail | center | 600px | Photos of the prototype 3-layer lens (a), and an exploded view showing the dimensions of each component (b).]]

== Simulation ==
The GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

The following is used to run the simulation for the focal plane:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams then pass through the prototype lens, being held in place by a special 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely. The focal distance is measured from the edge of the lens closest to the screen.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurements ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so it was replaced by the 530 nm green laser. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated through a polar angle of between 0° and 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye, a method of averaging was used (illustrated in the figure below) in order to record a more accurate and consistent focal distance. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points was recorded as the proper focal distance, and lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initially the lens holder was designed such that center of the lens was fixed when rotating through the polar angle. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup (illustrated below). A new lens holder was printed such that the lens rotated about its edge to compensate for this difference.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There was, however, still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle), the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points for the negative polar angles were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20° (purple) tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point, 10 measurements were done at both 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Understanding the Systematic Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position: a) a smaller radius of the second curved surface of the lens than was stated in the spec sheet, b) a larger refractive index of the NLaK33 glass layer, c) a smaller index of refraction of the mineral oil than was expected, or d) a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect on the focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the shift needed for the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

File:3CS Schematic.png

2017-08-03T19:27:45Z

Greg:

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T19:27:24Z

Greg:

A novel 3-layer spherical lens has been designed for the [https://eic.jlab.org/dirc/index.php/Main_Page Detection of Internally Reflected Cherenkov light (DIRC)] detector system to be used for the EIC. Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

[[File:3CS_Schematic.png | thumbnail | center | 600px | Photos of the prototype 3-layer lens (top), and an exploded view showing the dimensions of each component (bottom).]]

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate and consistent focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup (illustrated below). A new lens holder was printed to compensate for this difference.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20° (purple) tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position: a smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the NLaK33 glass layer, a smaller index of refraction of the mineral oil than was expected, or a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect on the focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

Mapping Focal Plane

2017-08-03T19:13:42Z

Greg: Greg moved page Mapping Focal Plane to 3-Layer Spherical Lens Focal Plane Mapping: Initial title was clumsy

#REDIRECT [[3-Layer Spherical Lens Focal Plane Mapping]]

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T19:13:41Z

Greg: Greg moved page Mapping Focal Plane to 3-Layer Spherical Lens Focal Plane Mapping: Initial title was clumsy

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate and consistent focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup (illustrated below). A new lens holder was printed to compensate for this difference.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20° (purple) tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position: a smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the NLaK33 glass layer, a smaller index of refraction of the mineral oil than was expected, or a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect on the focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T12:55:28Z

Greg: /* Resolving Shift */

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T12:44:39Z

Greg: /* Measurements with Tilted Lens */

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate and consistent focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup (illustrated below). A new lens holder was printed to compensate for this difference.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20° (purple) tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T12:42:37Z

Greg: /* Initial Results */

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate and consistent focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup (illustrated below). A new lens holder was printed to compensate for this difference.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20&deg (purple); tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T12:41:46Z

Greg: /* Initial Results */

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate and consistent focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup (illustrated below). A new lens holder was printed to compensate for this difference. Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20&deg (purple); tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T12:39:35Z

Greg: /* Measurement */

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate and consistent focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup. A new lens holder was printed to compensate for this difference. Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20&deg (purple); tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

3-Layer Spherical Lens Focal Plane Mapping

2017-08-03T12:38:22Z

Greg: /* Setup */

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser that shines through a 50/50 beam splitter and a mirror to make two parallel beams with a 1 mm separation. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup. A new lens holder was printed to compensate for this difference. Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20&deg (purple); tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

3-Layer Spherical Lens Focal Plane Mapping

2017-06-13T21:32:11Z

Greg: /* Resolving Shift */

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser shines through a 50/50 beam splitter and a mirror to make two parallel beams. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup. A new lens holder was printed to compensate for this difference. Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20&deg (purple); tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with our current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

3-Layer Spherical Lens Focal Plane Mapping

2017-06-13T21:31:27Z

Greg: /* Measurement */

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser shines through a 50/50 beam splitter and a mirror to make two parallel beams. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.png| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup. A new lens holder was printed to compensate for this difference. Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20&deg (purple); tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with out current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

File:Beam converge 0.1mrad.png

2017-06-13T21:31:05Z

Greg:

File:Focal plane xshift.png

2017-06-13T21:28:27Z

Greg:

File:Lens fpshift solutions.png

2017-06-13T21:28:14Z

Greg:

File:Focalplane all tilts.png

2017-06-13T21:27:09Z

Greg:

File:Focalplane corrections.png

2017-06-13T21:26:54Z

Greg:

File:Lens rotation point.png

2017-06-13T21:26:40Z

Greg:

File:Focalplane initial.png

2017-06-13T21:26:26Z

Greg:

File:Laser crossing.png

2017-06-13T21:25:35Z

Greg:

File:Lasertest1.jpg

2017-06-13T21:25:07Z

Greg:

File:Lens holder.png

2017-06-13T21:24:49Z

Greg:

File:Lens setup schematic.png

2017-06-13T21:24:26Z

Greg:

3-Layer Spherical Lens Focal Plane Mapping

2017-06-13T20:52:20Z

Greg: Created page with "Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the..."

Simulation predicts the shape of the focal plane of the new 3-layer lens design for the DIRC@EIC to be relatively flat, providing better focusing at the detector plane of the DIRC detector. A laser setup was built at Old Dominion University (ODU) to measure the focal plane of a prototype lens and verify the shape and position.

== Simulation ==
GEANT4 simulation package can be found here [https://github.com/hyperbolee/prtdirc].

To run lens measurement simulation for 3-layer lens:

<code>
./prtdirc -a 90 -h 1 -s 6 -x "opticalphoton" -p "2.33 eV" -g 0 -c 0 -gsy 0 -gsx 67.5 -e 10000 -b 1 -l 3 -t1 47.8 -t2 29.12 -tr 1 -t3 0 -gx 0 -gz 0</code>

Options: <code>-l</code> = lens code, <code>-t1</code> = radius of first layer [mm], <code>-t2</code> = radius of second layer [mm], <code>-tr</code> = separation between beams [mm], <code>-t3</code> = angle of lens tilt [degrees], <code>-gx</code> = shift of beams away from center in the direction perpendicular to a line connecting the beams [mm], and <code>-gz</code> = shift of beams away from center in the direction along a line connecting the beams [mm].

== Setup ==
The setup built at ODU (shown below) uses a 530 nm green laser shines through a 50/50 beam splitter and a mirror to make two parallel beams. The beams pass through a 30x40x60 cm3 glass fish tank filled with Britol 9NF White Mineral Oil with a refractive index similar to that of fused silica. The beams pass through the 3-layer prototype lens, being held in place by a 3D printed holder which rotates in one plane (called the tilt angle) and is attached to a rotation table on top of the tank that rotates in a perpendicular plane (called θ, or the polar angle). The beams are then focused onto a plastic screen inside the tank that is attached to a sliding track and allowed to move freely.

[[File:Lens setup schematic.png | thumbnail | center | 600px | Illustration of ODU laser setup (left) and a zoom-in of the lens holder and plastic screen (right).]]

[[File:Lens holder.png | thumbnail | center | 350px | 3D printed lens holder schematic.]]

[[File:Lasertest1.jpg | thumbnail | center | 350px | ODU setup showing lasers on and focusing on the screen.]]

== Measurement ==
Initial measurements were taken with a 632 nm red helium-neon laser, but the beam spot was too large and distorted, so the 530 nm green laser was used instead. Beams initially had a separation of 5 mm but were reduced to 1 mm in an effort to reduce effects from aberrations. In order to map the full focal plane for a fixed tilt angle the lens was rotated along the polar angle through up to 50° in 2° increments. Measurements were recorded at each step.

To compensate for the finite size of the beams and the poor resolution of the human eye a method of averaging was used (illustrated in the figure below) in order to record a more accurate focal point. Measurements were taken at the point where the beams seem to first converge and again where they first seem to diverge. The average position of these two points lead to a much more consistent measurement and better results.

[[File:Laser_crossing.pdf| frame | center | Illustration of two beams of finite size crossing. Any point between the two red circles could be seen as a "focal point" to the human eye, so the average position between these two points is taken to be the focal point.]]

== Initial Results ==
Initial measurements were taken with a 5 mm separation between beams and a lens holder that allowed rotation around the center of the lens. The results, shown below, were much more curved than expected from simulation. The first thought was to narrow the beams to a 2 mm, and finally 1 mm separation, but results were similar.

[[File:Focalplane initial.png | thumbnail | 500px | center | Initial results of measurements with 5 mm beam separation and center-rotated lens holder.]]

It was then deduced that in the simulation the beams always pass through the same point on the lens surface while, due to the rotation of the holder, they were passing through different points in the ODU setup. A new lens holder was printed to compensate for this difference. Another round of measurements showed that the original flat shape of the focal plane was recovered when using the new holder. The shape of the plane measured with the original holder was also compared to a modified version of the simulation that took the movement of the beams into account, and again the shape was very nicely reproduced. There is still a systematic shift in the absolute position of the focal plane of ~4cm, which will be addressed later in this article.

[[File:Lens rotation point.png | thumbnail | 350px | center | Illustration of the discrepancy between beam positions in data (black) and simulation (yellow) in relation to the original beam positions (blue) for a given rotation point
(red) at the center (top) of the lens, or at the edge (bottom) of the lens.]]

[[File:Focalplane corrections.png | thumbnail | 500px | center | Results of measurements of focal plane with lens rotating around its center (a) and its edge (b) after printing a new holder.]]

=== Measurements with Tilted Lens ===
Because the lens holder allows for a secondary plane of rotation (the tilt angle) the full 3D focal plane can be mapped. Below is a plot of the measured and simulated focal plane of 3-layer lens for 0°, 5°, 10°, and 20° tilt angles. For 0° and 10 ° the full plane was mapped for both positive and negative polar angles for sanity checks, while at 5° only a few points were selected, and at 20° tilt the beams were already too distorted for a proper measurement so no negative polar angles were measured. Again, the laser data nicely reproduces the simulation's shape, neglecting the 4 cm shift, up to 10° tilt, while going to larger tilts the finite size of the beams lead to too much distortion, making measurements unreliable and inaccurate.

[[File:Focalplane all tilts.png | thumbnail | 1000px | center | Measured (circles) and simulated (lines) focal plane of 3-layer lens for 0° (red), 5° (green), 10° (blue), and 20&deg (purple); tilt angles.]]

== Error Evaluation ==
To evaluate the error associated with the position of the focal point 10 measurements each were done at 0° and 10° polar angle rotation one after another to get the standard deviation of the measured positions. This resulted in a 0.29 cm uncertainty.

The uncertainty in the angle of the rotation table was assumed to be 1° as multiple alignments were done to set the lens to a "zero" position which resulted in a maximum deviation of 1°. The actual uncertainty in the rotation angle is likely much smaller.

== Resolving Shift ==
Several contributions were considered for explaining the 4 cm systematic shift of the focal plane position. A smaller radius of the second curved surface of the lens than was stated in the spec sheet, a larger refractive index of the center layer, a smaller index of refraction of the mineral oil than was expected, and a small converging angle of the beams off parallel could all explain this shift.

The following plot shows the effect of focal plane when changing each of these quantities such that the 0° tilt and 0° polar angle point matches that of the laser data (necessary changes shown in table).

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|-
! Quantity
! Change
|-
| Radius of second surface
| -1.3 mm
|-
| NLaK33 IoR
| +0.03
|-
| Oil IoR
| -0.15
|-
| Beam convergence
| 0.15 mrad
|}

[[File:Lens_fpshift_solutions.png| thumbnail | 500px | center|upright=0.7 ||alt=GEANT4 simulation modifications|Possible solutions to the systematic ~4 cm shift in the GEANT4 simulated focal plane compared to ODU measurements: decrease the radius of the
second layer by 1.3 mm (blue), increase the refractive index of NLaK33 by 0.03 (green),
decrease the index of refraction of the mineral oil by 0.15 (pink), and give a converging angle
of the laser beams of 0.15 mrad (black). Experimental data is shown in red.]]

The fact that the necessary change of the oil refractive index gives such a distorted shape rules out this possibility, while the very large deviation from the spec sheet of the refractive index of NLaK33 makes this option highly unlikely. To test the two remaining possibilities, a measurement of the focal plane with the beams off-center of the lens, shifted by 7 mm in the direction of a line connecting the two beams, was done and compared to simulation for both cases.

As shown in the plot below, the assumption of a converging beam angle agrees very nicely with the data, while the assumption of the smaller radius is too far shifted to describe the data.

[[File:Focal plane xshift.png | thumbnail | 500px | center | 7 mm shift of the beams off-center from the lens for data (red) and simulation assuming a decreased radius of the second curved surface (blue) and a converging beam angle of 0.1 mrad (green).]]

A second shift of the converging angle was checked for both 0° and 10° as well as the 7 mm off-center shift such that instead of the (0°,0°) point from data aligning with simulation, the simulation gave a more averaged description of the data. This was achieved with a 0.1 mrad converging angle. This explanation is the most reasonable in describing the shift of the focal plane position, as the numbers on the spec sheet for the prototype lens are unlikely to be so far off, and such a small angle leads to only a 1 mm change in distance over 10 meters, which is imperceptible with out current setup at ODU.

[[File:Beam converge 0.1mrad.png | thumbnail | 500px | center | upright=0.85 | Comparison of 0° tilt (red), 10° tilt (green), and 7 mm shift of beams (blue) with data (circles) and simulation (lines) using an assumption of 0.1 mrad beam deviation from parallel.]]

High-Performance Detection of Internally Reflected Cherenkov Light (DIRC)

2017-06-13T20:52:02Z

Greg: /* Ongoing studies */

== Summary of current status ==

The EIC DIRC design is inspired by the design of the PANDA Barrel DIRC detector and many synergies exist in the R&D processes of both projects. The primary goal of developing a high-performance DIRC is to have a compact device that can satisfy the PID requirements of the EIC.

[[File:DIRC2.png|frameless|center|upright=0.85]]

The baseline design, implemented in a Geant4 simulation, is shown above. The radiators are synthetic fused silica bars, each 4200 mm long, with a cross-section of 17 mm × 35.4 mm divided into 16 modules, called bar boxes. In each box eleven bars are placed side-by-side and separated by a small air gap. The 16 bar boxes are arranged in a barrel with a radius of 1m around the beam line. Mirrors are attached to one end of each bar. On the readout end, where photons exit the bar, a special 3-layer lens, that will be described further, is attached to each bar. The other side of the 3-layer lens is coupled directly to a prism that serves as an expansion volume. A zoom into the readout end of the bar box, showing details of the lens and prism section is shown on a right side of Fig. 4. The prism is made of fused silica, has a 38 degrees opening angle, and has dimensions of 284.3 mm × 390 mm × 300 mm. The detector plane of each prism is covered by 27,690 2 mm × 2 mm pixels giving a total of about 443,040 channels to record the location and arrival time of the Cherenkov photons.

The focus on the 3-layer lens is shown below:

[[File:DIRC1.png|frameless|center|upright=0.85]]

Example of performance for selected polar angle of 7GeV/c proton is shown here:

[[File:MCperformance.png|frameless|center|upright=0.85]]

The resolution of reconstructed Cherenkov angle depends on the pixel size of sensor. Geant4 study of that aspect is summarized on the plot:

[[File:PXsize.png|frameless|center|upright=0.85]]

== Ongoing studies ==

*[[CERN2015 Data Analysis]]

*[[Radiation Hardness at CUA ]]

*[[Mapping Focal Plane]]

Focal Plane measurements ODU

2017-02-15T03:33:26Z

Greg: Created page with "The setup for the focal plane measurements setup for the 3-layer lens at ODU can be found [https://userweb.jlab.org/~sallison/analysis/focalplane.php here]. The following plo..."

The setup for the focal plane measurements setup for the 3-layer lens at ODU can be found [https://userweb.jlab.org/~sallison/analysis/focalplane.php here].

The following plot shows the simulated (lines) and measured (dots) focal plane for lens holder tilt angles of 0 (black), 5 (blue), 10 (red), and 20 (green) degrees.

[[File:Focal_plane_data_sim.png|frameless|center|upright=4]]

File:Focal plane data sim.png

2017-02-15T03:15:24Z

Greg:

File:Focal plane setup laser ODU.jpg

2017-02-15T02:59:06Z

Greg:

NLaK Sample Measurement (170208)

2017-02-09T02:53:27Z

Greg:

[[File:NLaK1.jpg|thumbnail|right|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

[[File:NLaK3.jpg|thumbnail|right|upright=0.85 ||alt= NLaK sample in X-Ray setup. | NLaK sample in X-Ray setup. ]]

First set of measurements was done using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). We use X-Ray setup with 160 keV and 6.2 mA. Dose collected over 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png| thumbnail |center|upright=0.85 || alt= Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.| Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.]]

We don't see much of a scattering of the beam:

[[File:Beam.png| thumbnail|center|upright=0.85 || alt = Beam shape at the end of monochromator after going through NLaK sample (left), only air (right) | Beam shape at the end of monochromator after going through NLaK sample (left), only air (right)]]

Measurement was performed in steps ~100 or ~50 R. Since the setup during calibration showed 1.5 sec rise/dead time we decided to simply do multiplication of 6s irradiations (7.5 s actual irradiation). After each step we do transmission measurement in monochromator, followed by transmission measurement of reference sample of Fused Silica.

We observed significant drop in transmission already after first 100R irradiation, we decided to make smaller 50R steps afterwards. Unfortunately, the transmission drop continued linearry with further irradiation. Due to time limitation we stoped right now at 1kR.

[[File:Transmission.png| frame | center|upright=0.85| alt = Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) ]]

[[File:420nm_transmission.png| frame|center|upright=0.85| alt = Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) ]]

NLaK Sample Measurement (170208)

2017-02-09T02:48:20Z

Greg:

[[File:NLaK1.jpg|thumbnail|right|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

[[File:NLaK3.jpg|thumbnail|right|upright=0.85 ||alt= NLaK sample in X-Ray setup. | NLaK sample in X-Ray setup. ]]

First set of measurements was done using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). We use X-Ray setup with 160 keV and 6.2 mA. Dose collected over 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png| thumbnail |center|upright=0.85 || alt= Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.| Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.]]

We don't see much of a scattering of the beam:

[[File:Beam.png| thumbnail|center|upright=0.85 || alt = Beam shape at the end of monochromator after going through NLaK sample (left), only air (right) | Beam shape at the end of monochromator after going through NLaK sample (left), only air (right)]]

Measurement was performed in steps ~100 or ~50 R. Since the setup during calibration showed 1.5 sec rise/dead time we decided to simply do multiplication of 6s irradiations (7.5 s actual irradiation). After each step we do transmission measurement in monochromator, followed by transmission measurement of reference sample of Fused Silica.

We observed significant drop in transmission already after first 100R irradiation, we decided to make smaller 50R steps afterwards. Unfortunately, the transmission drop continued linearry with further irradiation. Due to time limitation we stoped right now at 1kR.

[[File:Transmission.png| thumbnail | center|| alt = Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) ]]

[[File:420nm_transmission.png| thumbnail|center|| alt = Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) ]]

NLaK Sample Measurement (170208)

2017-02-09T02:39:04Z

Greg:

[[File:NLaK1.jpg|thumbnail|right|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

[[File:NLaK3.jpg|thumbnail|right|upright=0.85 ||alt= NLaK sample in X-Ray setup. | NLaK sample in X-Ray setup. ]]

First set of measurements was done using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png| thumbnail |center|upright=0.85 || alt= Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.| Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.]]

We don't see much of a scattering of the beam:

[[File:Beam.png| thumbnail|center|upright=0.85 || alt = Beam shape at the end of monochromator after going through NLaK sample (left), only air (right) | Beam shape at the end of monochromator after going through NLaK sample (left), only air (right)]]

[[File:Transmission.png|center|| alt = Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) ]]

[[File:420nm_transmission.png| thumbnail|center|| alt = Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) ]]

NLaK Sample Measurement (170208)

2017-02-09T02:38:18Z

Greg:

[[File:NLaK1.jpg|thumbnail|right|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

[[File:NLaK3.jpg|thumbnail|right|upright=0.85 ||alt= NLaK sample in X-Ray setup. | NLaK sample in X-Ray setup. ]]

First set of measurements was done using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png| thumbnail |center|upright=0.85 || alt= Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.| Beam of monochromator right after NLaK (left) and Fused Silica (right) samples.]]

We don't see much of a scattering of the beam:

[[File:Beam.png| thumbnail|center|upright=0.85 || alt = Beam shape at the end of monochromator after going through NLaK sample (left), only air (right) | Beam shape at the end of monochromator after going through NLaK sample (left), only air (right)]]

[[File:Transmission.png| thumbnail|center|| alt = Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of wavelength for few selected cases. No Fresnel correction was applied (+4% to transmission) ]]

[[File:420nm_transmission.png| thumbnail|center|| alt = Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) | Transmission as a function of irradiation dose for 420nm in NLaK. Fused Silica plate is used as reference and is not irradiated. No Fresnel correction was applied (+4% to transmission) ]]

NLaK Sample Measurement (170208)

2017-02-09T02:32:57Z

Greg:

NLaK Sample Measurement (170208)

2017-02-09T02:29:53Z

Greg:

NLaK Sample Measurement (170208)

2017-02-09T02:28:59Z

Greg:

[[File:NLaK1.jpg|thumbnail|right|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

[[File:NLaK3.jpg|frameless|center|upright=0.85 ||alt= NLaK sample in X-Ray setup. | NLaK sample in X-Ray setup. ]]

We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:26:34Z

Greg:

[[File:NLaK1.jpg|thumbnail|right|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:25:52Z

Greg:

[[File:NLaK1.jpg|thumbnail|center|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:25:39Z

Greg:

[[File:NLaK1.jpg|frameless|center|upright=0.85 ||alt=NLaK Sample in holder in monochromator|NLaK Sample in holder in monochromator]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:23:44Z

Greg:

[[File:NLaK1.jpg|frameless|center|upright=0.85 ||alt=Alt text|NLaK Sample in holder in monochromator]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:21:37Z

Greg:

[[File:NLaK1.jpg|frameless|center|upright=0.85 |none |alt=Alt text|NLaK Sample in holder in monochromator]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:20:50Z

Greg:

[[File:NLaK1.jpg|frameless|center|upright=0.85 |alt=Alt text|NLaK Sample in holder in monochromator]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:19:40Z

Greg:

[[File:NLaK1.jpg|frameless|center|upright=0.85 text|NLaK Sample in holder in monochromator]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:14:33Z

Greg:

[[File:NLaK1.jpg|frameless|center|upright=0.85]]

''NLaK Sample in holder in monochromator.''

[[File:NLaK3.jpg|frameless|center|upright=0.85]]

''NLaK sample in X-Ray setup.''
We decided to do first set of measurements using only NLaK sample placing it in the centre of the X-Ray setup shelf, directly under the source. That allows to be sure about the dose rate.

[http://phynp6.phy-astr.gsu.edu/eRD14/index.php/X-Ray_setup_calibration_(170131) Calibration] of X-Ray setup was done using dosimeter with 15mm radius circular sensor, since dose depends on the area we normalized dose for NLaK piece (28x8 mm). Dose for 7.5 s using dosimeter on shelve 8 was measured to be 81.4 R, so for NLaK it should be ~25R.

We used monochromator to quantify influence of irradiation by measuring transmission. We also had Fused Silica plate used as reference to normalize NLaK measurements. Below one can see that the beam of monochromator nicely fits in samples.

[[File:BeamSamp.png|frameless|center|upright=0.85]]

"Beam of monochromator right after NLaK (left) and Fused Silica (right) samples."

We don't see much of a scattering of the beam:

[[File:Beam.png|frameless|center|upright=0.85]]

[[File:Transmission.png||center]]

[[File:420nm_transmission.png||center]]

NLaK Sample Measurement (170208)

2017-02-09T02:14:09Z

Greg:

NLaK Sample Measurement (170208)

2017-02-09T02:13:07Z

Greg:

X-Ray setup calibration (170131)

2017-02-09T02:11:42Z

Greg:

Calibration of X-Ray setup was performed using [http://www.raysafe.com/en/Products/Equipment/RaySafe%20ThinX#Downloads link RaySafe ThinX Rad] dosimeter (data sheet in link)

[[File:dosim.jpg|frameless|center|upright=0.85]]

Unfortunately, we discovered that dose of irradiation is not uniform in horizontal plane and some area were over the dosimeter limit. We were able to measure dose placing directly under the source of x-rays so we decided to calibrate setup only in center of each shelf (there are 9 shelves).

Dosimeter has a limit of exposure time so we set the X-Ray setup to 6s. We notice dosimeter shows irradiation time to be ~7.5s (additional raise/dead time). Dosimeter shows estimation for a minute and those values are in the plots. Below there is a table with all results. Measuring area of dosimeter is circle with 15mm radius.

[[File:XRay_dose.png|frameless|center|upright=0.85]]
''Distance (shelf) dependence of the dose rate in the x-ray machine. The dosimeter was always placed at the center of the shelf, and measured the doses at 3 different currents (1.0, 4.0, and 6.2mA)''
[[File:coeffs_mA.png|frameless|center|upright=0.85]]
''Linearity of dose rate as a function of current in X-Ray''

The dose rate follows very nicely the 1/d^2 rule (for distances greater than 20cm, i.e., shelves position from 1 to 8). Also, the dose rate is very linear with current set in the instrument.

Raw data:

[[File:calData.png|frameless|center|upright=0.90]]

File:Transmission.png

2017-02-09T02:11:41Z

Greg: Transmission vs wavelength for fused silica reference and NLaK at 0, 500, and 1000 rad doses

Transmission vs wavelength for fused silica reference and NLaK at 0, 500, and 1000 rad doses

X-Ray setup calibration (170131)

2017-02-09T02:11:29Z

Greg:

X-Ray setup calibration (170131)

2017-02-09T02:11:04Z

Greg: