Design and simulation of a GEM-based TEPC as a neutron REM meter.

A new plate-like tissue equivalent proportional counter (TEPC) based on the gas electron multiplier (GEM) is being developed for use as a neutron rem meter. The advantage of a plate-like TEPC over a conventional spherical TEPC is that several of the plate-like TEPCs can be stacked together as one unit to increase sensitivity to neutrons. A GEM-based TEPC consists of four layers of materials in a series: the front cover made of polyethylene, the cathode made of A-150 plastic, the gas region containing 1/3 atm of P-10 and 1/3 atm of nitrogen and the anode made of a copper-coated printed circuit board. The dimensions of the TEPC are 10 cm x 10 cm x 1.8 cm. The computer simulation shows that the neutron response function of the TEPC closely resembles the response curve of H(10) for neutrons with energies between 0.25 eV and 10 MeV. The corresponding sensitivity for such a TEPC for a bare (252)Cf neutron source was calculated to be 5.0 cpm per microSv h(-1). This sensitivity can be increased many times by simply stacking several TEPCs together as one unit.