Photosensors
The consideration of possible photosensor solutions for each detector component is driven by the operational parameters of the detector, with cost optimization in mind.
Photomultipliers (PMTs) from the currently available pool that are viable candidates for EIC application are Silicon PMTs (SiPMs), Multi-anode PMTs (MaPMTs), commercial Microchannel-Plate PMTs (MCP-PMTs), Large-Area Picosecond Photodetectors (LAPPDs), and Gaseous Electron Multipliers (GEMs). The key parameters of the photodetectors for the mRICH are small pixel size, resistance to magnetic field, and low cost (due to its large sensor area). Depending on the mRICH location, the requirement for radiation hardness will vary. The detector does not require good PMT timing resolution. GEMs with a photocathode sensitive to visible light, with their good radiation hardness and good position resolution, would be a very good and cost effective solution for the mRICH. SiPMs could be used if their radiation hardness is sufficient. LAPPDs with pixelized readout could be considered as possible photosensors for mRICH detectors if they have resistance to magnetic fields and low cost. MCP-PMTs satisfy the mRICH requirements, however their high cost is a drawback. The key parameter of the photodetectors for the Dual-radiator RICH is the small pixel size. Although the relative sensor area (normalized to the absolute detector area) of this detector is small, due to the large absolute detector area, cost is also an important parameter. Good sensor options for the Dual RICH would be similar to the ones for mRICH (keeping in mind that due to the location of the sensors, the requirement for radiation hardness is not as important for the Dual RICH). The key parameters of the photodetectors for a DIRC are fast timing, small pixel size, and a moderate to low dark count rate (DCR). Magnetic-field tolerance is required if the DIRC readout is located within the magnetic field of the solenoid. SiPMs could eventually be possible for DIRC if future developments lower their DCR to an acceptable level. Currently, the only photodetectors satisfying these requirements are MCP-PMTs (including LAPPDs with pixelized readout). Excellent timing resolution (~100 ps) is in particular required for the high-performance DIRC if a time-based PID reconstruction method is adopted for the geometry based on wide radiator plates. Such timing resolution is satisfied by currently commercially available MCP-PMTs, however, development of electronics with good time resolution for small signals may be required.
