GEM-MIGAS Electron Multiplier Operation in Argon-Methane Mixtures

A Gas Electron Multiplier with a Micro-Induction Gap Amplifying Structure (GEM-MIGAS) is formed when a conventional GEM is operated with a short induction gap, typically 50 mum. A three-dimensional electric field simulation of a GEM-MIGAS detector was performed in order to evaluate the electric field profile in the different regions of the structure. Different electrostatic conditions were undertaken to forecast the detector performance in gas medium. An experimental study of GEM-MIGAS operating in an Ar/CH₄ (90/10%) gas mixture, in pure CH₄ and in pure Ar was carried out. Performance characteristics including charge gain and energy resolution for 5.9 keV X-rays are presented.