Development and Fielding of a Spectrometer for High Flux CW/Pulsed Neutron Beam Characterization*

Fast, high-flux neutrons are an attractive source for imaging due to their ability to penetrate high-Z materials. Intense neutron sources also provide a powerful tool to measure neutron scattering cross sections needed to advance basic and applied nuclear science and engineering. However, intense continuous neutron sources are difficult to characterize due to the inapplicability of traditional time-of-flight techniques and detection challenges associated with high count rates.  A novel neutron diagnostic system for use at an advanced fast neutron imaging facility is being developed at Lawrence Livermore National Laboratory (LLNL). This scatter time-of-flight (sTOF ) neutron spectrometer will: (1) have high energy resolution for fast neutrons; (2) be compatible with both low current, pulsed neutron sources and high current, continuous neutron beams; and (3) function in a high radiation background environment. A successful first test of the sTOF spectrometer was conducted at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory using neutrons produced from a 14 MeV deuteron beam incident on a 3.7-mm-thick carbon target. These results were compared to literature data as well as neutron foil activation analysis results.