The hybrid μ-RWELL for ePIC Endcap tracking

The Electron Ion Collider (EIC) at Brookhaven National Laboratory (BNL) aims to investigate the nuclear structure with unprecedented precision, focusing on confinement and non-perturbative QCD behavior. ePIC (Electron-Proton/Ion Collider) is the primary candidate experiment at EIC, with a hermetic design meant to measure scattered particles over a wide kinematic range. The detector’s tracking system is composed of silicon trackers and Micro Pattern Gaseous Detectors (MPGD). The MPGD Endcap Trackers consist of four G-RWELL disks, a hybrid layout integrating a GEM-based pre-amplification stage over the classic -RWELL, covering the region with pseudo-rapidity and the entire azimuthal angle. Prototypes with an active area of 10 × 10 cm2 were tested at CERN PS-T10 beam line with a 5 GeV/c muon beam in November 2024. The charge centroid and TPC reconstruction methods were used to measure spatial resolution and efficiency at various angles. The data was acquired using an SRS system with APV25 front-end electronics and analyzed with the ROOT-based Corryvreckan framework. The detectors appear stable up to very high gas gains, reach an efficiency of 96% for both perpendicular and inclined tracks, and a spatial resolution of 90 um and 200 um respectively.