Measurement of basic features of Thick-GEM and Resistive-GEM

Abstract

Recently, Thick-GEM (TGEM) whose geometry is at the millimeter-scale has been developed to overcome the disadvantages of micro-scale Gas Electron Multiplier (GEM) such as fragility against a discharge, difficulty in obtaining enough gain at low pressure and so on. In addition, TGEM with resistive electrodes (RETGEM) also has been developed to make TGEM more tolerant with a discharge. Active research is carried out worldwide for applications such as liquid Argon detectors, Cerenkov light detectors, sampling elements in calorimeter and low-pressure time projection chamber. TGEM and RETGEM look very promising, but their basic properties have not yet been studied thoroughly. TGEM and RETGEM with different geometries were made and the basic properties such as the voltage dependence of gain, the energy resolution and the gain variation as a function of time at different gain levels were measured. A gain of about 104 was obtained with Ar(90%) + CH4 (10%) gas mixture for both TGEM and RETGEM. The gain variation as a function of time of TGEM at the gain ∼ 2000 was within 6% after the correction by pressure and temperature. On the other hand, the gain variation as a function of time of TGEM was large at higher gain and can not be explained by only the correlation between the gain and the value of pressure over temperature. The gain variation as a function of time of RETGEM was within 4% after the correction by pressure and temperature. The achieved energy resolution was ∼ 13% (TGEM) and ∼ 10% (RETGEM). The energy resolution of RETGEM is comparable to that of micro-scale GEM.