a Study of Micromegas with Preamplification with a Single GEM

A MICROMEGAS detector was combined with a single GEM to allow preamplification before primary electrons enter the main detector. The preamplification not only extends the maximum achievable gas gain without discharge but also it minimizes spark rates when exposed to high intensity ionizing particles. We performed both laboratory and beam tests with various gas mixtures to find optimal operational characteristics and the results were encouraging and this particular combination may be suitable for experiments that require high counting rates and good spatial resolution as in VLHC.