Pulse height fluctuations of integrated micromegas detectors

Recent publications report that Micromegas-based detectors exhibit very good energy resolution for gaseous radiation detectors. When made in microtechnology, the physical dimensions of such a detector can be controlled with micrometer precision over a large area. In this paper we report an energy resolution of 5.2% r.m.s. at 5.9 keV of such a detector (called InGrid) and present experimental and simulation results to explain and quantify the contributions to the gain fluctuations. Our results may be applicable also for other micropattern gas detectors.