Studies Of Digital Filter Process Techniques For Nuclear Signal

Digital signal processing techniques are profoundly developed in nuclear physic field with the development of high-speed ADC, programmable logic devices (FPGA and CLPD), real-time operating system and microprocessor. In nuclear detection, the incident particles firstly are converted to electric signals by the detector, and then the signals are amplified by the pre-amplifier and the main amplifier before the ADC. In this process, the noise could be introduced. Thus, the background of the environment and the noise contribute a lot to the statistical fluctuations of the sampled pulse data. The effects of the noise can affect both the energy resolution and measurement precision. On the other hand, digital signal processing techniques are widely discussed in digital nuclear instrument, and digital filter is one of the key techniques in digital signal processing. This paper aims to studying the applications of digital filters in signal processing.In the study of digital filter, nuclear pulse signal is simulated. The signal is always superposed by noise and the amplitude of signal follows a normal distribution. The interval time of the signal is distributed exponentially, while the signal itself is regarded as decay exponential distribution. Both the ideal nuclear signals and the signals with noise are simulated as the original signals for digital filter. FIR filter and S-K filter are studied based the simulated signals. The principles of the parameters selection are also involved by some experiments. By comparing the functions of FIR filter and S-K filter for nuclear pulse signal, the advantages of the S-K filter are proposed. The experiment results show that the S-K filter is better than FIR filter and the S-K filter can improve energy resolution more efficient than the FIR filter. However, under the condition of high counting rate, the total counts of the spectrum obtaining by S-K filter is smaller than that of spectrum obtaining by FIR filter because the pulse width is expanded by S-K filter.In the real hardware platform, FIR filter is injected in the system to guarantee the energy resolution. In the experiments of highly-radioactive source, the FIR filter can increase the throughput and improve the energy resolution at the same time.