Design of active-type personal dosemeter for high energy neutrons

A systematic design of an active-type personal dosemeter for high-energy neutrons up to 100 MeV has been tried in the procedures of (1) selection of a detector element, (2) neutron irradiation experiments, (3) development of calculation model for predicting the dosemeter response to neutrons, and (4) improvement in the energy dependence of the dosemeter. A thin fully-depleted Si detector (e.g. ΔE detector) was selected as one of promising detector elements because of a fewer influence by gamma-rays and a reasonable response to charged particles. Neutron irradiation experiments were carried out in mono-energetic fields, where pulse height distributions were measured using Si detector covered with a polyethylene sheet. A theoretical model has also been developed in a simple geometry consisting of Si and a radiator, based on the angular differential cross section and the proton range-energy relation. A good agreement in the shape and absolute value was confirmed between the calculated distributions and the measured pulse height spectra. In addition, the two-window technique and two-detector method have been applied to improve a large dependence on the neutron energy. (author)