A digital multi-channel system based on parallel full comparison baseline restoration method

This paper designs a baseline estimation digital energy spectrum measurement system using a parallel full-comparison method, aimed at reducing the impact of baseline drift on the energy resolution of the digital energy spectrum measurement system. The system consists of two parts: an analog baseline adjustment circuit and a digital baseline estimation module. The digital module first performs baseline estimation, then transmits the results to the frontend circuit to adjust the baseline, thereby correcting drift caused by circuit noise and signal pulse stacking. The system is mainly composed of a DAC baseline adjustment circuit, an ADC sampling circuit, and an FPGA-based digital multi-channel analysis system, in which a parallel full-comparison mean baseline estimation method is deployed to calculate the baseline adjustment amount. To verify the reliability of the system, NaI detectors were used in this study, and the energy resolution and response of the system were tested using dual-source <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup>Cs and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup>Co. The experimental results show that the linear response fitting of the digital multi-channel energy spectrum measurement system exceeds 99.99%. Under high counting rates, the energy resolution without baseline recovery was 8.83% (@0.662 keV), while the energy resolution with the parallel full-comparison baseline recovery method was 7.57% (@0.662 keV), improving by 0.92%. In conclusion, compared to the system without baseline recovery, the parallel full-comparison baseline recovery method effectively alleviates the baseline drift issue of the NaI detector under high counting rates, thereby improving the energy resolution of the system.