Prototype of carbonless MRPC for MARQ experiment

Abstract

The MARQ (Multi-Purpose Analyzer for Resonance and Quark Dynamics Spectrometer) experiment, an upcoming project at J-PARC in Japan, focuses on the development of two types of Multigap Resistive Plate Chambers (MRPCs) for tracking and time-of-flight (TOF) measurements. A critical issue during MARQ MRPC development was the shortage of carbon tape used as high-voltage electrodes. To address this difficulty, a small prototype with carbonless high-voltage electrode is built. A carbonless MRPC was designed with a 1-stack, 5-gap configuration, featuring 0.26 mm gaps and a 20 cm $\times$ 20 cm active area. The carbonless high-voltage electrodes are composed of an array of copper pads connected via 100 k$\Omega$ resistors, serve as quenching resistors. Both high-voltage electrodes and readout strips are integrated into a single multi-layer Printed Circuit Board (PCB). The prototype also incorporates factory-made mylar spacers to reduce the aging effects of fishing-line spacer and solid-silicon gaskets to ensure robust gas sealing. Performance was evaluated using an electron beam with a rate of approximately 10 Hz/cm${}^2$, achieving around 95% efficiency and a time resolution of approximately 95 ps. However, stability remains a concern, as the efficiency decreases after two days of continuous beam operation. The suspected cause is current leakage within the multi-layer PCB. In the future, a thicker PCB will be tested to prevent the potential current leakage between high-voltage electrode and readout layer.