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Tham khảo tài liệu 'photodiodes communications bio sensings measurements and high energy part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Detection of VUV Light with Avalanche Photodiodes 211 Fig. 2. Schematic of the Gas Proportional Scintillation Counter instrumented with an APD as the VUV photosensor. The geometry of the GPSC was chosen to allow some of the X-ray photons to reach the APD without being absorbed in the gas which allows direct X-ray interactions in the APD concomitant with X-ray interactions in the gas. A typical pulse-height distribution is presented in Fig.3 for a GPSC with argon filling irradiated with 5.9-keV X-rays. The main features of the pulse-height distributions include the scintillation peaks resulting from the full absorption of X-rays in the gas and from events with subsequent argon fluorescence escape from the active volume the so-called escape peaks as well as the electronic noise tail. An additional peak resulting from direct absorption of the 5.9-keV X-rays in the APD is also present in the pulse-height distributions. This latter peak is easy to identify since its amplitude depends only on the APD biasing and not on the GPSC biasing being present even when the gas proportional scintillation counter biasing is switched off. Knowing the w-value - i.e. the average energy to produce an electron hole pair - of silicon for X-rays wsi 3.6 eV the peak resulting from the direct interaction of 5.9-keV X-rays in the APD can be used to determine the number of charge carriers produced by the VUV-light pulse. In the case of Fig.3 the amount of energy deposited in silicon by the argon scintillation pulse is similar to what would be deposited by 30-keV X-rays directly absorbed in the APD. This feature allowed the absolute determination of the argon and the xenon scintillation yields given the quantum efficiency of the APD and the solid angle subtended by the APD relative to the region where the scintillation occurred 37-40 . The performance characteristics of the APD in VUV light detection has been investigated as a function of voltage applied to the APD using the information of the
