Development of a portable high-energy neutron spectrometer

Abstract

The design of a portable high-energy (20-800 MeV) neutron spectrometer based on CsI or BaF2 is described. The particle discrimination properties of these scintillators allow the light-ion spallation products (p, d, t and alpha) from neutron interactions to be identified uniquely. One or more of the resulting pulse-height spectra can be unfolded to reveal the incident neutron spectrum. Dosimetric quantities can then be calculated based on the unfolded spectrum. Due to the high stopping power of these scintillators, modest-sized crystals are suitable for this application. Combined with advances in electronics, a lightweight instrument capable of on-line particle discrimination with a real-time display of neutron-induced count rate is feasible. Preliminary experimental data are presented, and the importance of validating MCNPX-generated response functions is discussed. A brief discussion on future work follows.

CHELSI: Recent developments in the design and performance of a high-energy neutron spectrometer

“…The detector was based on a 1 00 Â 1 00 CsI(Tl) scintillator coupled to a Hamamatsu R6095 PMT as described previously [1]. The anode signal was fed to a current-tovoltage converter to preserve signal shape.…”

“…A program to develop such an instrument is underway at LANL [1]. Nicknamed CHELSI, the instrument is based on the well-known pulse shape discrimination properties of CsI(Tl) [2][3][4][5].…”

CHELSI: a portable neutron spectrometer for the 20-800 MeV region

“…The CsI probe assembly can be readily removed from the housing and used in conjunction with Polaris, a bench top digital spectrometer as described previously (1)(2) .…”

“…A method of determining the absolute charged particle count rate per unit fluence rate was described earlier (2) . Figure 3 also includes data previously obtained at 33 and 60 MeV at the Universite de Catholique Louvain in Louvain-laNeuve (1) , Belgium.…”

“…In previous publications (1)(2) , we have detailed the evolution of a novel neutron spectrometer for use in high-energy neutron fields. It is designed to be lightweight and portable while providing real time dose data to the operator.…”