Development and performance evaluation of Thick-GEM

A Gas Electron Multiplier with a thick insulator such as a 100 mum or 150 mum thick insulator (Thick-GEM) has been developed by dry etching successfully in Japan. The electric field inside a hole of the Thick-GEM was calculated and the basic properties of the Thick-GEM were measured. A much stronger electric field can be realized inside the hole of the Thick-GEM than that of a GEM with a 50 mum thick insulator (Standard-GEM). The Thick-GEM can attain much higher gain than the Standard-GEM and has a good gain stability within 1.0% for 9 hours. In this paper, the characteristics of the Thick-GEM are described compared with the Standard-GEM.