The micro-RWELL detector for the LHCb Muon system phase-2 upgrade

The micro-RWELL is a single amplification stage resistive Micro-Pattern Gaseous Detector, realized with a copper-clad polyimide foil patterned with a micro-well matrix and coupled with the readout PCB through a DLC resistive film ($10\div100$ MOhm/$\square$). The detector is proposed for several applications in HEP that require fast and efficient triggering in harsh environment (LHCb muon-upgrade), low mass fine tracking (FCC-ee, CepC) or high granularity imaging for hadron calorimeter applications (Muon collider). For the phase-2 upgrade of the LHCb experiment, proposed for LHC Run-5, the excellent performance of the current muon detector will need to be maintained at 40 times the pile-up level experienced during Run-2. Requirements are challenging for the innermost regions of the muon stations, where detectors with rate capability up to 1 MHz/cm$^2$ and capable to stand an integrated charge up to 10 C/cm$^2$ are needed. In this framework an intense optimization program of the micro-RWELL has been launched in the last years, together with a technology transfer to the industry operating in the PCB field. In order to fulfill the requirements, a new layout of the detector with a very dense current evacuation grid of the DLC has been designed. The detector, co-produced by the CERN-EP-DT-MPT Workshop and the ELTOS Company, has been characterized in terms of rate capability exploiting a high intensity 5.9 keV X-ray gun with a spot size ($10\div50$ mm diameter) larger than the DLC grounding-pitch. A rate capability exceeding 10 MHz/cm$^2$ has been achieved, in agreement with previous results obtained with m.i.p. at PSI.