Investigation of FPGA-Based Real-Time Adaptive Digital Pulse Shaping for High-Count-Rate Applications

Digital signal processing techniques have been widely used in radiation spectrometry to provide improved stability and performance with compact physical size over the traditional analog signal processing. In this paper, field-programmable gate array (FPGA)-based adaptive digital pulse shaping techni...

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Bibliographic Details
Published in:IEEE transactions on nuclear science 2017-07, Vol.64 (7), p.1733-1738
Main Authors: Saxena, Shefali, Hawari, Ayman I.
Format: Article
Language:English
Subjects:
Adaptive algorithms
Algorithms
Compensation
Data processing
Digital filters
Digital signal processing
Digital signal processing (DSP)
Digital signal processors
Digitization
Digitizing
Energy
Energy consumption
Energy resolution
Field programmable gate arrays
Filtering algorithms
filters
Germanium
Low-pass filters
Noise reduction
Preamplifiers
Pulse amplitude
Pulse shaping methods
Radiation
Real time
Rejection
Restoration
Signal processing
Signal processing algorithms
Spectrometry
Spectroscopy
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Summary:Digital signal processing techniques have been widely used in radiation spectrometry to provide improved stability and performance with compact physical size over the traditional analog signal processing. In this paper, field-programmable gate array (FPGA)-based adaptive digital pulse shaping techniques are investigated for real-time signal processing. National Instruments (NI) NI 5761 14-bit, 250-MS/s adaptor module is used for digitizing high-purity germanium (HPGe) detector's preamplifier pulses. Digital pulse processing algorithms are implemented on the NI PXIe-7975R reconfigurable FPGA (Kintex-7) using the LabVIEW FPGA module. Based on the time separation between successive input pulses, the adaptive shaping algorithm selects the optimum shaping parameters (rise time and flattop time of trapezoid-shaping filter) for each incoming signal. A digital Sallen-Key low-pass filter is implemented to enhance signal-to-noise ratio and reduce baseline drifting in trapezoid shaping. A recursive trapezoid-shaping filter algorithm is employed for pole-zero compensation of exponentially decayed (with two-decay constants) preamplifier pulses of an HPGe detector. It allows extraction of pulse height information at the beginning of each pulse, thereby reducing the pulse pileup and increasing throughput. The algorithms for RC-CR 2 timing filter, baseline restoration, pile-up rejection, and pulse height determination are digitally implemented for radiation spectroscopy. Traditionally, at high-count-rate conditions, a shorter shaping time is preferred to achieve high throughput, which deteriorates energy resolution. In this paper, experimental results are presented for varying count-rate and pulse shaping conditions. Using adaptive shaping, increased throughput is accepted while preserving the energy resolution observed using the longer shaping times.
ISSN:0018-9499
1558-1578
DOI:10.1109/TNS.2017.2692219