The Bonner sphere is the canonical example of instruments that provide a measure of neutron spectra by using moderating and absorbing materials together with thermal-neutron detectors. For such spectrometers, the instrument response reflects a statistical average of the energy spectrum. Pacific Northwest National Laboratory has developed neutron-sensitive cerium-activated scintillating fibers composed of lithium-silicate glass. These fibers present an enabling technology for efficient neutron spectroscopy. A moderating spectrometer was built as a testbed for materials identification. Based on the results of Monte Carlo experiments, six fiber layers are separated by polyethylene layers whose thickness has been chosen to maximize neutron spectral information. The completed, self-contained instrument, including electronics and data logging computer has a mass less than 35 kg, slightly more than half of which is polyethylene. Measurements have been performed by this instrument with various sources representing hard and soft neutron spectra. Because this instrument is a technology testbed, the data are recorded as pulse-height spectra. Results and future directions are presented.
Revised: April 19, 2010 |
Published: August 3, 2001
Citation
Bliss M., R.A. Craig, D.S. Barnett, D.N. Anderson, J.E. Smart, M.A. Knopf, and S.A. Hartley. 2001.Performance of a Moderating Neutron Spectrometer That Uses Scintillating Fibers. In 42nd Annual Meeting, Proceedings of the Institute of Nuclear Materials Management. Deerfield, Illinois:Institute of Nuclear Materials Management.PNNL-SA-35087.