An aging study of a MICROMEGAS with GEM preamplification

We have conducted the first study of the aging behavior of a MICROMEGAS detector with gas electron multiplier (GEM) preamplification. Because a MICROMEGAS is constructed with minimal insulation and because the electric field is parallel to the amplification gap, superior radiation hardness was previously reported in an Ar-Isobutane gas mixture in a stand-alone device. The MICROMEGAS is expected to tolerate an even larger accumulated charge in a cleaner gas mixture, such as Ar-CO2. However, using a MICROMEGAS as a stand-alone device in this mixture could increase discharge probability and lead to faster degradation in detector performance. We show that this problem can be circumvented by employing GEM preamplification. Although it has been previously shown that a GEM ages when operated at a large gain, sharing the gain between a MICROMEGAS and the GEM creates a high-gain, very radiation-hard gas detector. We find that a MICROMEGAS + GEM combination exhibits no deterioration in performance after a total charge accumulation of 23 mC/mm(2). (C) 2003 Elsevier B.V. All rights reserved