Microdosimetric Measurements in Gamma and neutron Fields with a Tissue Equivalent Proportional Counter Based on a Gas Electron Multiplier

A multi-element tissue-equivalent proportional counter (TEPC), based on a single gas electron multiplier (GEM) foil of standard geometry, has been constructed with 16 cylindrical sensitives volumes. In this article, the design of this novel counter is described and first microdosimetric measurements are presented. To study the response of the GEM-TEPC to both low and high linear energy transfer radiation fields, the microdosimetric spectra due to a (137)Cs gamma-ray source and to fast neutrons from (7)Li(d,n)(8)Be reaction have been measured using pure propane gas at low pressure, in order to simulate a tissue site of about 1 μm equivalent size. The comparison with spectra measured with a spherical TEPC and with a mini-TEPC demonstrates promising properties for application of the GEM-TEPC for microdosimetric applications