R&D on a novel spectro-imaging polarimeter with Micromegas detectors and a Caliste readout system

Micromegas detectors, part of the Micro-Pattern Gaseous Detectors (MPGD) family, are used in a very wide range of applications in the High Energy Physics community but also in astroparticle and neutrino physics. In most of the Micromegas applications the design of the detector vessel and the readout plane is extremely coupled. A way of dissociating these two components would be by separating the amplification structure and the detector volume from the readout plane and electronics. This is achieved with the so called piggyback Micromegas detectors. They open up new possibilities of applications in terms of adaptability to new electronics. In particular piggyback resistive Micromegas can be easily coupled to modern pixel array electronic ASICs. First tests have been carried out with a Medipix chip where the protection of the resistive layer has been proved. The results of very recent tests coupling piggyback Micromegas with the readout module of Caliste are presented. Caliste is a high performance spectro-imager with event time-tagging capability, able to detect photons between 2 keV and 250 keV in the context of a spatial micro spectro-imaging polarimetrer. In the current application, with the Piggyback Micromegas, we use the readout module only as the sensitive detector. We benefit of the good spatial resolution thanks to the high density readout pixels (~600 μm pixel pitch), to the low noise, to the low power and to the radiation hard integrated front-end IDEF-X electronics. The advantage of such a device is to have a high gain, low noise, low threshold, and robust detector operating at room temperature. This would be very attractive for spatial applications, for instance X-ray polarisation