Determination of neutron fluence in 1.2 and 2.5 MeV mono-energetic neutron calibration fields at FRS / JAEA

*A highly efficient silicon semiconductor detector with a polyethylene convertor (CH2-SSD) was developed and the neutron fluences were precisely evaluated with it at 1.2 and 2.5 MeV mono-energetic neutron calibration fields at the Facility of Radiation Standard (FRS) in the Japan Atomic Energy Agency (JAEA) using an accelerator. The CH2-SSD was designed to have a higher detection efficiency than that of the conventional one in order to measure the neutron fluencies at the calibration point of more than 100 cm from the target. The NRESP-ANT and PHITS codes were used to calculate the efficiency of the CH2-SSD and its uncertainties. The maximum neutron fluence rates at 100 cm from the target were evaluated to be 1.0×10 3 and 2.0×10 3 cm -2 s -1 in the 1.2 and 2.5 MeV fields, respectively. They are high enough to calibrate dosemeters