The μ-RWELL for high rate application

Abstract

The micro-Resistive WELL (μ-RWELL) is a compact, simple and robust Micro-Pattern Gaseous Detector (MPGD) developed for large area HEP applications requiring the operation in harsh environment. The detector amplification stage, similar to a GEM foil, is realized with a polyimide structure micro-patterned with a blind-hole matrix, embedded through a thin Diamond-Like-Carbon (DLC) resistive layer with the readout PCB. The introduction of a resistive layer (0ρ=50÷20 MΩ/□) mitigating the transition from streamer to spark gives the possibility to achieve large gains (>104), while affecting the detector performance in terms of rate capability. Different detector layouts have been studied: the most simple one based on a single-resistive layer, with edge grounding has been designed for low-rate applications (few tens of kHz/cm2); more sophisticated schemes have been studied for high-rate purposes (0⩾1 MHz/cm2). An overview of the different architectures studied for the high-rate version of the detector, together with their performance will be presented. The presence of the resistive layer also affects the charge spread on the strips and consequently the spatial resolution of the detector: a systematic study of the spatial resolution obtained with the charge centroid (CC) method as a function of the impinging angle was made. For non-orthogonal tracks the spatial resolution with CC method is compared with the performance obtained with the micro-TPC mode (μTPC): a readout approach that exploits the combined measurement of the ionization clusters time of arrival and the amplitude of the signals on the strips. Implementing the μTPC allows reaching an almost flat space resolution <100 μ m for a wide angular range. Finally the results of the detector aging campaign is presented, with detectors integrating up to 175 mC/cm2 and bare DLC foils integrating a charge up to 800 mC/cm2.