1. Performance Tests Of External Moderators Of A PGNAA Setup
Naqvi, AA; Fazal-ur-Rehman; Al-Jarallah, MI; Abu-Jarad, F; Maslehuddin, M
PERGAMON-ELSEVIER SCIENCE LTD, APPLIED RADIATION AND ISOTOPES; pp:
27-38; Vol: 58
King Fahd University of Petroleum & Minerals
Summary
Performance tests of external cylindrical moderators of an accelerator-based prompt
gamma ray neutron activation analysis (PGNAA) setup have been carried out through
thermal neutrons and prompt gamma-ray yield measurements. The PGNAA setup is
to be used for analysis of cement samples. This study was conducted to investigate the
effects of geometry of cylindrical moderator on yield of thermal neutrons and prompt
gamma-rays for two different types of moderator assemblies. One of the moderators
was to be used with a small sample and the other to be used with a large sample. Fast
and thermal neutron yield was measured inside the sample volume as a function of the
front moderator thickness as well as sample length. Neutron yield measurement was
carried out at the King Fahd University of Petroleum and Minerals 350 keV pulsed
beam accelerator using nuclear track detectors. The pulsed 200 keV deuteron beam
with 5 ns pulse width and kHz frequency was used to produce MeV
neutrons via D(d,n) reaction. Neutron yield measurements showed that the large
sample moderator has a smaller yield of thermal neutrons as compared to the small
sample moderator, which is in complete agreement with the results of Monte Carlo
yield calculations of the thermal and fast neutrons from both the moderators. Finally,
the prompt gamma-ray yield from a Portland cement sample was measured using the
two moderators and was compared with each other, As predicted by Monte Carlo
simulations, in spite of a smaller yield of thermal neutrons, the large sample
moderator has a higher yield of prompt gamma-rays. (C) 2002 Elsevier Science Ltd.
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