Neutron Coincidence Counting with Digital Signal Processing

Neutron coincidence counting is the reference 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/SCA producing a train of TTL pulses that are fed into an electronic unit which performs the time correlation analysis. Under a push from the main inspection authorities (IAEA, Euratom and 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 PC¿s 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 the pre-delay 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 inter-comparison benchmark exercise on the analysis software for pulse processing.

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; 

2009-09-09

ELSEVIER SCIENCE BV

JRC51981

0168-9002,   

www.elsevier.com/locate/nima,    https://publications.jrc.ec.europa.eu/repository/handle/JRC51981,   

10.1016/j.nima.2009.07.029,