Electrical investigation of LIGA-processed gas electron multipliers

Gas electron multipliers (GEMs), which have square-shaped micro-holes, have been realized by using a deep-etch X-ray lithographic technique or LIGA process. In order to understand the operation of such a gas avalanche microdetector, we have performed electric field simulations by using three-dimensional finite-element methods. The most important electrical characteristic, the gas avalanche gain, of the LIGA-processed GEM has been measured with regards to two-different charge-collection geometries, open and closed GEM geometries. The measurement results for the gas avalanche gain over a wide range of thicknesses are presented. Other electrical characteristics, such as the pulse-height spectra and the time stability, are also presented.