Development of New Front-end Readout Electronics for γ-γ Coincidence Measurement System

A new front-end readout electronics was developed, which was used for research and testing of the prototype coincidence measurement system in the heavy-ion cancer therapy device. The circuit mainly includes the energy measurement chain, time measurement chain and data processing unit. The energy measurement chain is composed of an anti-aliasing filter with a cut-off frequency of 7 MHz and an analog-to-digital converter (ADC), which forms a waveform sampling circuit. The time measurement chain is composed of a timing discrimination circuit formed by high-speed comparator and a time-to-digital converter (TDC). The data processing unit is designed and implemented based on a field programmable gate array (FPGA). The linearity of the circuit is better than 0.8% and the noise is less than 0.8 mV (RMS). It was tested coupled with a LaBr₃ crystal strip, and the energy resolution is 4.5% (FWHM). Meanwhile, the test was performed with the LYSO crystal detection array, and the position map scatter plot is clear. The performance of the developed front-end readout circuit is superior to the CAMAC system and has a good practical application prospect.