Reducing Ion Backflow with a novel MPGD structure using a bulked micro-mesh on a GEM

Abstract

Due to their simplicity and accuracy for reconstructing particle trajectories, Micromegas (Micro-MEsh-GAseous Structure) and Gas Electron Multiplier (GEM) detectors are commonly used as readout systems in Time Projection Chambers (TPCs). The main limitation of these two types of detectors is the ion backflow (IBF), which may result in space charge in a TPC. We present in this article a new Micro-Pattern Gaseous Detector (MPGD) structure, which combines a micro-mesh and a set made of a GEM surmounted by a micro-mesh at only a few hundreds μm above. We report the performance results of two prototypes using this new structure, and compare them to a single Micromegas and a hybrid detector composed of a Micromegas and a GEM with a few millimeters gap. Finally, we show that this new detector is capable of reducing the ion backflow to less than 0.2% for a total gain of around 2000.