The Measurement of Fast Neutron Flux over the Neutron Energy Range 0.03 MeV to 3.0 MeV

Abstract

Measurements of neutron flux in the neutron energy region 0.03 MeV to 3.0 MeV have been made using a proton recoil counter and a Hanson-McKibben type long counter. Several proton recoil counters filled with different gases at different pressures have given flux measurements self-consistent to 2%. The long counter has been calibrated against photo-neutron sources at a number of energies and also against the recoil counter. The variation of its efficiency as determined by the two methods is in satisfactory agreement. The absolute calibration of the long counter with respect to a RdTh-D2O source whose strength was known to ?2?% agreed with the calibration with respect to the recoil counter to 1%. A similar cross check with an Ra-Be source gave an initial discrepancy of 15% but this was traced to an error in the source strength and variation with energy in the response of the long counter. These cross checks are satisfactory and over the major portion of the energy range the standard error is not more than ?3%.