Simulation and First Test of a Microdosimetric Detector Based on a Thick Gas Electron Multiplier

We present design of a new microdosimetry detector based on thick gas electron multiplier (THGEM). A prototype detector was designed for a cylindrical sensitive volume with 5 mm diameter and 5 mm height. To optimize the avalanche gain, the electron avalanche process was modeled by varying THGEM thickness, hole diameter and high voltage bias for the tissue-equivalent propane gas. For a THGEM with 0.6 mm thickness and 0.3 mm hole diameter, the theoretical avalanche gain reached ~ 200 at a 800 V THGEM bias. The prototype detector was fabricated and tested using the McMaster
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Li(p,n) neutron source. The avalanche gain of the prototype detector was comparable with the gain of the standard microdosimetry detector. Additional THGEMs with various thicknesses were fabricated and are under tests.