NLaK Sample Measurement (170208)

NLaK Sample in holder in monochromator

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.

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.

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

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

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.

Transmission as a function of wavelength for few selected cases. 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)