A new technique for fabrication of a Gas Electron Multiplier

The Gas Electron Multiplier (GEM) represents one of the most promising micro-pattern detectors for providing stable, charge multiplication over a wide range of active areas, and with genuinely affordable and reproducible fabrication methods. Several important characteristics of the GEM remain to be investigated and optimized. One key feature is the charging-up of the dielectric insulating layer of GEMs and its dependence on hole geometry. Using an epoxy-based photoresist, we are developing a fabrication technique that naturally generates purely cylindrical holes in the GEM electrode, a geometry that has been found by previous researchers to minimize or eliminate this effect. This report describes the principle of the fabrication technique and presents experimental results of energy resolution, gain, rate capability and potential for large area applications. These compare favorably with the attributes of existing techniques