title: Reset charge sensitive amplifier for NaI(Tl) gamma-ray spectrometer.
abstract: The time constant of the output signal of the front-end readout circuit of a traditional gamma-ray spectrometer with a NaI(Tl)+PMT structure is affected by temperature, measurement environment and the signal transmission cable, so it is difficult to get a good resolution spectrum, especially at higher counting rates. In this paper, a reset charge sensitive amplifier (RCSA) is designed for the gamma-ray spectrometer with a NaI(Tl)+PMT structure. The designed RCSA outputs a step signal, thus enabling the acquisition of double-exponential signals with a stable time constant by using the next stage of a CR differentiating circuit. The designed RCSA is mainly composed of a basic amplifying circuit, a reset circuit and a dark current compensation circuit. It provides the output step signal through the integration of the PMT output charge signal. When the amplitude of the step signal exceeds a preset voltage threshold, it triggers the reset circuit to generate a reset pulse (about 5µs pulse width) to reset the output signal. Experimental results demonstrated that the designed RCSA achieves a charge sensitivity of 4.26×10(10)V/C, with a zero capacitance noise of 51.09fC and a noise slope of 1.98fC/pF. Supported by the digital shaping algorithm of the digital multi-channel analyzer (DMCA), it can maintain good energy resolution with high counting rates up to 150kcps and with a temperature range from -19°C to 50°C.
authors.affiliation: Chengdu University of Technology, Sichuan 610059, China. Electronic address: zgq@cdut.edu.cn.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Zeng
authors.affiliation: Chengdu University of Technology, Sichuan 610059, China.
authors.forename: Chengjun
authors.initials: C
authors.lastname: Tan
authors.affiliation: Chengdu University of Technology, Sichuan 610059, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Chengdu University of Technology, Sichuan 610059, China.
authors.forename: Liangquan
authors.initials: L
authors.lastname: Ge
authors.affiliation: Chengdu University of Technology, Sichuan 610059, China.
authors.forename: Xiyao
authors.initials: X
authors.lastname: Liu
authors.affiliation: Chengdu University of Technology, Sichuan 610059, China.
authors.forename: Qun
authors.initials: Q
authors.lastname: Luo
keywords: Equivalent noise charge (ENC); NaI(Tl) gamma-ray spectrometer; Photomultiplier tube (PMT); Reset charge sensitive amplifier (RCSA)