Cherenkov Light Emission in Pure Cherenkov Emitters for Prompt Gamma Imaging

Proton range verification (PRV) in proton therapy by means of prompt-gamma detection is a promising but challenging approach. High-count rates, energies ranging between 1 and 7 MeV, and a strong background complicate the detection of such particles. In this work, the Cherenkov light generated by prompt-gammas in the pure Cherenkov emitters thallium bromide, thallium chloride (TlCl) and PbF2 was studied. Cherenkov light in these crystals can provide a very fast timing signal with the potential to achieve very high-count rates and to discern between prompt-gammas and background signals. Crystals of $1\times 1$ cm2 and thicknesses of 1, 2, 3, and 4 cm were simulated. Different photodetector (PD) configurations were studied for 2.3, 4.4, and 6.1-MeV prompt-gammas. TlCl achieved the greatest number of detected Cherenkov photons for all energies, detector dimensions, and PD efficiency modeling. For the highest-prompt-gamma energy simulated, TlCl yielded approximately 250 Cherenkov detected photons, using a hypothetical high-performance PD. Results show the crystal blocks of 1 cm $\times1$ cm $\times1$ cm have greater prompt-gamma detection efficiency per volume and a comparable average number of detected Cherenkov photons per event.