Development of highly efficient proton recoil counter telescope for absolute measurement of neutron fluences in quasi-monoenergetic neutron calibration fields of high energy

Shikaze, Yoshiaki ; Tanimura, Yoshihiko   ; Saegusa, Jun; Tsutsumi, Masahiro

In precise calibration of the monitors and the dosimeters for high energy neutrons, it is desirable to evaluate the neutron fluence at a reference point. In order to evaluate the neutron fluence of the quasi-monoenergetic neutron fields, a proton recoil counter telescope (PRT) with high efficiency has been developed for the absolute measurements at the reference point. Relatively large design of the PRT's components contributed to high detection efficiency at the reference point with a large irradiation area at a long distance from a target. The converter thicknesses were adjusted to keep same carbon density per unit area for easy background subtraction. As a result of the high detection efficiency and the adjustment, statistical precision could be improved. Neutron fluences were evaluated with uncertainties within 6% on the basis of the analysis of measured data and of the detection efficiency calculated by using the MCNPX code.