Development of a New Method for Measurement of Neutron Detector Efficiency up to 20 MeV

Abstract

A new approach to neutron detector efficiency detemination has been taken. A neutron detector has been calibrated with a 252 Cf source at low energy. The calibration can be extended to energies above 8 MeV with accelerator-based neutron sources. This techniques uses the fact that the cross section for a symmetric reaction with nucleus of atomic number A yielding a final nucleus with atomic number (2A − 1) and a neutron A + A → (2A − 1) + n. This reaction must be symmetric about 90 • in the center-of-mass system. The laboratory energies for the neutrons at the paired energies differ substantially. Thus, an efficiency known at one of the two angles can be used to determine the efficiency to higher energies or, for a negative Q, to lower neutron energies.

Toward a New Evaluation of Neutron Standards

“…The results are systematically slightly larger than the evaluated values but generally within their uncertainties of 1.1 to 2% (note that all uncertainties in this paper are one standard deviation uncertainties). Additional work [4] at the Ohio University Accelerator Laboratory on the hydrogen standard now emphasizes the small angles in the center of mass system (CMS) at about 10 and 14 MeV where very few data are available.…”