MICROMEGAS: high rate and radiation hardness results

In this report, we present results of gain studies using various gas mixtures in a novel structure of a gaseous detector called MICROMEGAS which is under development at Saclay. We in particular studied the maximum of gain achievable with MICROMEGAS before the discharge. We tried various gas mixtures (argon, neon, CF/sub 4/) with various proportions of quencher (isobutane, cyclohexane, DME). We also studied the radiation hardness of MICROMEGAS using argon-isobutane and CF/sub 4/-isobutane mixtures.