A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is accurate and sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of praesodymium, an element that has a single, naturally occurring isotope (Pr-141), a significant (n,2n) cross section, and decays by positron emission. Neutron fluences are measured by using the sum-peak method to count gamma-ray coincidences from the annihilation of the positron decay product. The system was tested using 14 and 2.45 MeV neutron bursts produced by NSTec Dense Plasma Focus Laboratory fusion sources. Comparisons with lead, copper, beryllium and silver activation detectors have been performed. The detection method allows measurement of 14 MeV neutrons with a total error of ± 10%.

Date Published: 11 September 2009
PDF: 6 pages
Proc. SPIE 7449, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XI, 744912 (11 September 2009); doi: 10.1117/12.830039

Published in SPIE Proceedings Vol. 7449:
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XI
Ralph B. James; Larry A. Franks; Arnold Burger, Editor(s)