ABSTRACT
The traditional nuclear pulse signal generator outputs the nuclear pulse signal of specific waveform according to the input pulse amplitude probability distribution and counting rate, following the signal output laws of radiation detector in both pulse amplitude and time interval. However, the output waveform is generally regulated by an analog circuit, with the single waveform and difficult parameter adjustment. In this study, the digital C-R and R-C filters were explored, a cascading digital C-R or R-C filter algorithm was proposed, realizing multiple pragmatic nuclear pulse signal outputs through the serial or parallel connection of multiple digital filters. The actual test results show that the nuclear pulse signal generator constructed by this algorithm can simulate the nuclear pulse signals under different detectors and counting rates, thus expanding the scope of application and improving the flexibility of digital nuclear pulse signal generators.
ABSTRACT
Semiconductor detector is widely used in energy dispersive X-ray fluorescence measurements due to its excellent performance. In this paper, Si-PIN and CdTe semiconductor detectors were studied, performances of the two detectors were compared in material properties, detection efficiency, energy resolution and other aspects. Focused on the performance of the detectors influenced by the thickness of detector sensitive area, energy of incident X-ray, shaping time of post-stage circuit, and analyzed the differences of energy spectrum caused by escape peaks and hole trailing. Aiming at the problem of incomplete hole collection in detector, a digital multi-channel analyzer (DMCA) based on FPGA with rise-time discriminator was designed, it could reduce the influence of hole trailing effectively and improve energy resolution. The experimentation results indicate that the detection efficiency of Si-PIN and CdTe is roughly equal when energy is below 15 keV while CdTe has much higher detection efficiency than Si-PIN when energy is above 15 keV. The optimum forming time of the Si-PIN detector is about 10 µs, and the CdTe detector is about 2.6 µs, so the CdTe detector is more suitable for the high count rate condition. Si-PIN detector has better energy resolution than CdTe detector for different energy incident X-ray. CdTe detector has obvious hole tailing effect and the energy resolution of CdTe detector is significantly improved by using DMCA with rise-time discrimination.
