Figure 1: PE Counts Per Incident Gamma

Gamma PE count figures are given above. The data file used to collect this is stored under: /data/chocula/schmitz/condor_output/HannahTestStand/data/paper/gamma/EURECA.root.

The macro used to collect these images was under: /home/schmitz/sim/HannahTestStand/macros/GammaPMTHit.C.

These 511 keV gamma PE counts represent optical photoelectron (PE) detections by the PMT, generated by an incident 511 keV gamma. That is, the PEs have been generated, become incident on the PMT, then “passed” the PMT quantum efficiency successfully to register as a detection. This is then a histogram of the PE detections per incident gamma.

The geometry used to collect this data was the optics geometry, with 1mm embedded fiber, 0.5mm PTFE wrapping, PTFE reflectivity = 0.95, and a 8cm long scintillator sample (no Gd). Gammas were made incident at a location 4 cm down the axis of a 2.5 cm diameter plastic (polystyrene, C8H8) scintillator. The gammas were made incident perpendicular to the axis of the scintillator at this location, with an initial position of 10 cm radially offset from the scintillator axis (so as to travel through the entire diameter of the plastic).

The quantum efficiency and scintillation spectra were implemented based on direct measurements by DMP. The refractive index and absorption lengths were set at a constant 1.58 and 2.5m, respectively. The PMT was set to have zero reflectivity, such that every time a PE became incident on its face it was terminated, with or without detection depending on the result of the quantum efficiency check. The WLS fiber didn't have much impact, but its various optical properties were set using the details in the Y11 text files (Y11-abslength.txt, Y11-emit.txt) as well as using fiberPSTabsorb.txt for the absorption length details.

As a general note for people who saw the previous version of this PE chart before I updated the scintillation spectrum, the resulting PE counts are about 50% of what they used to be.