Understanding avalanches in a Micromegas from single-electron response measurement

摘要: Abstract Avalanche fluctuations set a limit to the energy and position resolutions that can be reached by gaseous detectors. This paper presents method based on laser test-bench measure absolute gain relative variance of Micro-Pattern Gaseous Detector from its single-electron response. A Micromegas detector was operated with three binary gas mixtures, composed 5% isobutane as quencher, argon, neon or helium, at atmospheric pressure. The anode signals were read out low-noise, high-gain Cremat CR-110 charge preamplifiers enable detection down 5× 10 3 for first time. argon mixture shows lowest given amplification field together breakdown limit, which is 2×10 4 an order magnitude lower than helium. For each gas, f almost unchanged in range studied. It found twice higher ( ~0.6) two other mixtures. hierarchy agrees predictions analytic models, ionisation yields, Monte-Carlo model included simulation software Magboltz version 10.1.