A study of a combination of MICROMEGAS + GEM chamber in Ar-CO/sub 2/ gas

A MICROMEGAS is a micropatterned gaseous detector that has great potential in many applications including high energy physics and astronomy. The detector consists of a micromesh supported by thin pillars (50 /spl mu/m) and the space between the micromesh and the anode plane defines an amplification gap. The detector has a high rate capability and good spatial resolution. The performance of the MICROMEGAS can be improved by adding a preamplification device like a GEM to factor the gas multiplication into two stages. With the added preamplification, it is possible to minimize spark rates in detecting heavily ionizing particles without sacrificing gas gain significantly. The additional gas gain provided by the GEM also allows the detector to operate in a clean gas mixture like Ar-CO/sub 2/. The use of a clean gas mixture allows the device to be radiation hard.