X-ray imaging with gaseous detectors using the VMM3a and the SRS

The integration of the VMM3a Application-Specific Integrated Circuit (ASIC) into RD51's Scalable Readout System (SRS) provides a versatile tool for the readout of Micro-Pattern Gaseous Detectors (MPGDs). With its self-triggered high-rate readout, its analogue part that allows to get information on the deposited energy in the detector, and its so-called neighbouring-logic that allows to recover information on the charge distribution, this new system has features of particular interest for digital X-ray imaging. In the present article, we want to emphasise the capabilities of VMM3a/SRS by presenting results of X-ray imaging studies. We will highlight the advantages on the energy and the spatial resolution provided by the neighbouring-logic. In the first part, we focus on spatial resolution studies. We show how segmented readout structures introduce a repeating pattern in the distribution of the reconstructed positions (using the centre-of-gravity method) and how this behaviour can be mitigated with the neighbouring-logic. As part of these studies, we explore as well an alternative position reconstruction algorithm. In the second part of the article, we present the energy resolution studies.