Characterization of a resistive Micromegas detector with capacitive-sharing pad readout

We report on the performance of a resistive Micromegas detector equipped with a novel readout architecture that achieves high spatial resolution while significantly reducing the number of readout channels. The concept relies on capacitive charge sharing within a vertical stack of four pad layers embedded in a 2 mm-thick PCB. This multilayer structure distributes the signals induced by the avalanches generated in the Micromegas amplification gap across multiple pads of the anode plane, resulting in a lateral broadening of the induced signal. The extent of charge sharing is set by the pad geometry and layout in the stacks, allowing an optimal distribution of signal among neighbouring readout elements. The capacitive-sharing stack is produced with standard PCB techniques, ensuring scalability and straightforward integration. A prototype was characterized with X-rays in the laboratory and with a muon beam at the CERN Super Proton Synchrotron (SPS). It operated stably at high gain, delivered spatial resolutions of 1/20 and 1/30 of the pad pitch for 5 mm and 10 mm pads, respectively, and reached a detection efficiency of 98% at plateau with tracks perpendicular to the detector plane. The detector performance was also studied in detail for tracks incident at non-perpendicular angles (achieving efficiencies close to 100%), exploiting the timing information of the hits to refine the spatial reconstruction.