Development of cylindrical type proton-recoil proportional counter and its use for absolute measurements of neutron fluences at 144, 250 and 565 keV monoenergetic calibration fields

Saegusa, Jun; Tanimura, Yoshihiko   ; Yoshizawa, Michio  

A proton-recoil proportional counter has been developed as a standard instrument for evaluating neutron fluence at the accelerator-based neutron calibration field. The counter consists of a cylindrical cathode and an external housing in which hydrogen is filled as counting gas. For neutrons in the energy range between 50 keV and 1 MeV, the fluence of the neutron field can be determined by an absolute measurement with the counter. The developed counter was used for determining the reference neutron fluence of the monoenergetic neutron fields at the Facility of Radiation Standards of JAEA. For the 144, 250 and 565 keV neutron fields, it has been able to measure the fluences with the standard uncertainties less than 2 %. The measured fluences for 144 and 565 keV have showed good agreement with the values estimated by another measurements with a transfer instrument traceable to primary standards.