基于基线自动恢复技术的数字多道能谱仪

摘要

[Background] The baseline drift of detector output could result in spectrum drift and energy resolution loss of the multi-channel spectrometer. Though baseline estimation approaches can obtain the baseline of nuclear signals, they are not able to reduce the effect of baseline drift on the front-end circuit. [Purpose] This study aims to design and implement a multi-channel spectrometer with auto-baseline restoration functionality. [Methods] First of all, the baseline of detector's output is estimated by using minimum average method and implemented in the field-programmable gate array (FPGA). Then the estimation value is sent to micro-controller unit (MCU) for regulation condition judgment, and to digital-to-analog converter (DAC) for necessary baseline adjustment. Finally, the baseline of detector output is restored in the front-end circuit. A multi-channel spectrometer is designed based on LaBr3(Ce) detector and this auto-baseline restoration functionality. [Results] The experimental results imply that the designed multi-channel spectrometer can realize baseline restoration automatically. [Conclusion] Under the situation of high radioactivity, the baseline drift of detector output can be solved by this multi-channel spectrometer, and the energy resolution of the system can remain stable.%不同放射性强度的测量应用中,探测器输出核脉冲信号的基线将发生漂移,进而造成多道能谱仪的谱线漂移和能量分辨率损失.尽管采用数字基线估计方法可以对核脉冲信号的基线进行正确估计,但纯数字基线恢复算法无法有效处理核脉冲信号基线漂移对前端电路的影响.采用最小平均值基线估计方法,先在现场可编程门阵列(Field-Programmable Gate Array, FPGA)中进行数字基线估计;然后通过SPI总线将基线估计值传入微控制器(Micro-Controller Unit, MCU),MCU根据基线值判断是否进行基线调节,将基线估计值传入数模转换器(Digital-to-analog Converter, DAC);最后在前端电路中实现核脉冲信号的基线恢复.基于LaBr3(Ce)探测器的测试结果表明:采用该基线自动恢复技术的数字化多道能谱仪能够实现核脉冲信号的基线自动恢复.在高放射性测量条件下,测量系统能够解决因基线漂移引起的谱线漂移问题,使系统能量分辨率保持稳定.