A new signal readout method for position-sensitive multi-output detectors,such as those in high-energy spectroscopy measurement and nuclear imaging,was developed by combining the charge division circuit,summing circuit and charge-to-time conversion(QTC) circuit.The 64 outputs of a Hamamatsu H8500 position-sensitive photomultiplier tube were processed,and three digital pulses were generated.The widths of digital pulses were determined using the time-to-digital converter in an field programmable gate array.The energy and position information of incident y-rays is estimated based on the proportionality between the width of digital pulses and input charge created by y-photons.A prototype was built using discrete components and tested,and the energy and position resolutions were improved compared with that obtained with standard ADCs.This method greatly simplifies the front-end electronics and the digital interface.It enables a compact electronics system and an easy integration into an ASIC.
A method and system for automatically and simultaneously measuring the light output of multiple scintillators,or each scintillating unit of an array,were developed.Using a large area flat panel PSPMT H8500,the light output and energy resolution were obtained automatically by comparing with reference scintillators or array using an Energy Table,Look-up Table and energy spectrum data.The aim of developing an efficient performance evaluation of scintillators was achieved.Using the method,a scintillator performance testing system was set up and six LYSO crystals and a 3×3 LYSO array were measured.The results showed that the light output and energy resolution were accurately measured automatically.The deviation of repeat measurements for the same sample was not more than 2%,and the nonlinear deviation of the system was not more than 3%.The system is suitable for measuring the performance of crystals,especially where the mass measurement of crystals and arrays is required.
