Nuclear Signal Processing Research Articles

Review of Research on Nuclear Signal Pulse Shaping

Pulse shaping can greatly improve the signal-to-noise ratio and has been widely used in nuclear signal processing. This paper gives a brief overview of the current research status of nuclear signal pulse shaping at home and abroad. It describes in detail the three traditional pulse shaping methods of quasi-Gaussian shaping, triangular shaping and trapezoidal shaping, and discusses the nuclear pulse signal shaping that has appeared in recent years. And a brief introduction to the nuclear pulse signal shaping methods that have emerged in recent years is also given.

Design and implementation of a virtual nuclear pulse signal generator

This paper presents a virtual nuclear pulse signal generator. The pulse generator can be used in specific scenarios such as calibration and maintenance of nuclear detection systems, validation of nuclear signal processing algorithms, and nuclear physics teaching experiments, as a substitute for real radioactive sources and detectors to generate nuclear pulse signals. This helps to avoid exposing experimental personnel to radiation hazards. The pulse generator is capable of generating specific nuclear pulse signals according to experimental requirements, and these signals has the same physical characteristics as real nuclear pulse signals, including amplitude distribution, time and amplitude randomness. In the pulse generator, we conducted theoretical analysis of the radioactive source and detector, and established a model library for both, to obtain crucial parameters of the nuclear pulse signals. The pulse generator is built on a hardware framework with field-programmable gate array (FPGA) as the core, utilizing these key parameters to generate signals with realistic physical characteristics of nuclear pulse signals, including amplitude and time characteristics. The counting rate of the output nuclear pulse signals can be adjusted by configuring the hardware parameters of the pulse generator.

Improvement in Trapezoidal Pulse Shaping Pile-Up in Nuclear Signal Processing

In digital nuclear spectroscopy, trapezoidal shaping is widely used. Compared with traditional CR-RC4 semi-Gaussian shaping, it has a better energy resolution and higher counting rates, but does not void the pulse pile-up in the case of extreme counting rates. In this paper, a new recursive algorithm is proposed that can improve the anti-pile-up ability, and is easy to implement in any DSP-based processor that is used in any digital pulse shaping filter section. The complete deduction and simulation are presented in this paper.

Design and characterization of third-order Sallen–Key digital filter in nuclear signal processing

The Gaussian filter shaping circuit is widely used in the nuclear pulse signal processing due to its good performance in amplitude extraction and pulse counting. A third-order Sallen–Key (3rd S–K) filter shaping circuit is designed based on a RC integrator and a second-order Sallen–Key (2nd S–K) circuit. According to the digital 3rd S–K, the transfer functions is derived in the Laplacian domain, and the numerical recurrence model is analyzed and researched, the purpose is to obtain its transfer function and amplitude–frequency response curve in the z-domain. For the simulation and actual sampling of the nuclear signal, digital shaping processing is performed at different parameters, three parameters (d, SNR, δ) are defined to compare and analyze the amplitude extraction, noise suppression and symmetry of the digital shaping method, which shows that as the shaping parameters increases, the digital shaping output noise suppression performance is better, the SNR increased from 49.25 to 64.21, the waveform is more symmetrical, the δ reduced from 34.05 to 0.22. At the same parameters, it is compared and analyzed with CR-RC3 and 2nd S–K shaping methods, according to the digital Gaussian shaping results, the 3rd S–K digital shaping method has better pulse amplitude extraction(d = 36.06%), noise suppression performance (SNR = 64.21) and waveform symmetry (δ = 0.22). Under different shaping methods, the energy resolution and pulse counting rate of the Fe characteristic X-ray energy spectrum are compared based on a Si-PIN detector. The results show that the 3rd S–K digital shaping method has better energy resolution performance and comprehensive performance indicators, which can be further applied for digital shaping of nuclear pulse signals.

Identification and correction method of nuclear detector pulse forming pile-up

Gaussian forming has good time, response and SNR, Gaussian shaping is widely used in nuclear signal processing because of its simple realization and good comprehensive performance. When working in high counting rate environment, the output pulse signal of nuclear detector often appears pile-up phenomenon, which leads to the nuclear spectrum measurement system cannot accurately extract the pulse amplitude, and then the energy spectrum measurement error. In order to solve this problem, a method of pulse pile-up identification and correction is proposed. A test system consisting of signal generator, detector, communication circuit and oscilloscope is designed. Experiments show that this method can accurately identification and correct the pile-up waveform., and increase count rate by 3%–30% compared with the traditional method.

Model-Based Pileup Events Correction via Kalman-Filter Tunnels

A Kalman-filter-based method is proposed to address challenges in nuclear signal processing, including pileup events and noise cancelation. The state-transition equation is established on the basis of suitable pulse shape models. By regarding the output signal of particle detectors as a measurable variable, the measurement equation is also introduced to correct dynamic processes of the state transition. A linear Kalman filter with $n$ tunnels is constructed to separate pileup events and maintain the original waveforms of pulses. In addition, two terms are defined and addressed for separation operations, namely, Availability , which is used to prepare for upcoming events, and Clearance Mechanism , which is given to remove thumbnail information from the previous events and make occupied tunnels available to subsequent nuclear events. Simulation and field experiments demonstrate that the proposed method can handle critical situations of pulse pileup and minimize count loss and dead time in the X-ray energy spectrum while maintaining the original pulse shapes.

The development of Campbell integration system applied in high particle flux measurement

Campbell Mode is a method widely used in nuclear signal processing. In this article, we introduce the design of the new system based on the Campbell integration measurement applied in NFM (neutron flux measurement) systems for ITER plasma diagnose. In this article, we introduce a digital particle flux measurement system based on Campbell integration theory. A subsequent series of experiment are conducted to test the digital Campbell system performance, which proves that the Campbell integration system is competent for the plasma diagnose in ITER.

Implementation of a cusp-like for real-time digital pulse shaper in nuclear spectrometry

Pulse shaping, which improves signal-to-noise ratio excellently, has been extensively used in nuclear signal processing. This paper presents a cusp-like pulse-shaping technique developed through the recursive difference equation in time domain. It can be implemented in field programmable gate array hardware system. Another flat-topped cusp-like shaper is developed to optimize the time constant of pulse shaping and reduce the influence of ballistic deficit. The methods of both baseline restoration and pile-up rejection are described. The 137Cs energy spectra measured with the digital cusp-like shaper are 6.6% energy resolution, while those by traditional analog pulse shaper are 7.2% energy resolution, under the same conditions. This technique offers flexibility, too, in adjusting the pulse shaper parameters.