Photosensors for PET scanner on the base of BaF2 crystals

We suggest the use of crystal of BaF2 as scintillator in Positron Emission Tomography (PET) with very high space resolution at the level of 1–2 mm. These crystals are prospective candidates to provide necessary cell granularity (crystal+photodetector) of 2×2 mm2 and they possesses a very short decay time (∼0.8 ns) of the fast component in the emission spectrum. In order to detect this emission lying within deep ultra-violet (UV) spectral range with wavelengths 195–240 nm we propose to develop new type of photodetecting devices. These ones are based on wide band gap group-III nitride compounds (A3N) having an adjustable spectral sensitivity at wavelengths 210–360 nm and quantum efficiency 10–15%. The principal schemes of such devices based on A3N-nanoheterostructures emitting photoelectrons into vacuum or gaseous atmosphere and detector of photoelectrons are discussed in this paper. The photo-device with parallel-plane gas positron sensitive detector having time and position resolutions 1 ns and 500 μm, respectively, can work at counting rate up to 108 ph cm−2 s−1.