Neutron coincidence counting with digital signal processing

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 608; no. 2; pp. 316 - 327
• Main Authors: Bagi, Janos, Dechamp, Luc, Dransart, Pascal, Dzbikowicz, Zdzislaw, Dufour, Jean-Luc, Holzleitner, Ludwig, Huszti, Joseph, Looman, Marc, Marin Ferrer, Montserrat, Lambert, Thierry, Peerani, Paolo, Rackham, Jamie, Swinhoe, Martyn, Tobin, Steve, Weber, Anne-Laure, Wilson, Mark
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 11.09.2009
• Subjects: Calibration of neutron counters; Monte Carlo codes; Neutron coincidence counting; Neutron detectors; Nuclear safeguards; Calibration of neutron counters; Monte Carlo codes; Nuclear safeguards; Neutron detectors; Neutron coincidence counting
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2009.07.029

Neutron coincidence counting is a widely adopted nondestructive assay (NDA) technique used in nuclear safeguards to measure the mass of nuclear material in samples. Nowadays, most neutron-counting systems are based on the original-shift-register technology, like the (ordinary or multiplicity) Shift-Register Analyser. The analogue signal from the He-3 tubes is processed by an amplifier/single channel analyser (SCA) producing a train of TTL pulses that are fed into an electronic unit that performs the time- correlation analysis. Following the suggestion of the main inspection authorities (IAEA, Euratom and the French Ministry of Industry), several research laboratories have started to study and develop prototypes of neutron-counting systems with PC-based processing. Collaboration in this field among JRC, IRSN and LANL has been established within the framework of the ESARDA-NDA working group. Joint testing campaigns have been performed in the JRC PERLA laboratory, using different equipment provided by the three partners. One area of development is the use of high-speed PCs and pulse acquisition electronics that provide a time stamp (LIST-Mode Acquisition) for every digital pulse. The time stamp data can be processed directly during acquisition or saved on a hard disk. The latter method has the advantage that measurement data can be analysed with different values for parameters like predelay and gate width, without repeating the acquisition. Other useful diagnostic information, such as die-away time and dead time, can also be extracted from this stored data. A second area is the development of “virtual instruments.” These devices, in which the pulse-processing system can be embedded in the neutron counter itself and sends counting data to a PC, can give increased data-acquisition speeds. Either or both of these developments could give rise to the next generation of instrumentation for improved practical neutron-correlation measurements. The paper will describe the rationale for changing to the new technology, give an overview of the hardware and software tools available today and a feedback of the experience gained in the first tests. Associated with the experimental tests, the ESARDA-NDA working group is also performing an intercomparison benchmark exercise on the analysis software for pulse processing.