Design of a Low Power Digital MCA Module for In-situ Environmental Gamma-ray Measurement

In-situ gamma-ray detection is an important method for environmental radioactivity measurement. In order to improve the performance and save power consumption, analog shaping electronics are beginning to be replaced by digital signal processing methods. As an essential part of an in-situ gamma-ray spectroscopic system, a digital multi-channel analyzer (MCA) module with 8 independent readout channels is developed and described in this paper. The MCA module is designed with low power consumption (1.0 W in total at 40 MS/s, 0.7 W at 10 MS/s) and small size, which is based on an 8-channel power-efficient ADC and a flash-based FPGA. Signals are digitized and processed individually in each readout channel. Digital filters with adjustable parameters and energy analysis are realized in the flash-based FPGA. Combined with a quasi-hemispherical structure CdZnTe (CZT) detector and accompanying front-end analog electronics, the function of digital signal processing has been verified, and the performance of the digital MCA has been tested. Results show that the energy resolution is 1.84% (FWHM) at 662keV, which is close to the intrinsic resolution of the tested quasi-hemispherical CZT detector.