Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers

TL;DR

This study measures and optimizes the electrical properties of electrode materials for bakelite RPCs, demonstrating how silicone coatings influence resistivity, efficiency, and noise rates in particle detection.

Contribution

It provides a detailed analysis of how silicone coatings affect surface resistivity and detector performance in bakelite RPCs, with comprehensive electrical property measurements and optimization strategies.

Findings

Silicone coatings reduce surface resistivity and improve efficiency.

Efficiency > 90% achieved with optimized silicone coating.

Surface resistivity correlates with detector noise rates.

Abstract

Single gap (gas gap 2 mm) bakelite Resistive Plate Chamber (RPC) modules of various sizes from 10 cm \times 10 cm to 1 m \times 1 m have been fabricated, characterized and optimized for efficiency and time resolution. Thin layers of different grades of silicone compound are applied to the inner electrode surfaces to make them smooth and also to reduce the surface resistivity. In the silicone coated RPCs an efficiency > 90% and time resolution \sim 2 ns (FWHM) have been obtained for both the streamer and the avalanche mode of operation. Before fabrication of detectors the electrical properties such as bulk resistivity and surface resistivity of the electrode materials are measured carefully. Effectiveness of different silicone coating in modifying the surface resistivity was evaluated by an instrument developed for monitoring the I-V curve of a high resistive surface. The results indicate definite correlation of the detector efficiency for the atmospheric muons and the RPC noise rates with the surface resistivity and its variation with the applied bias voltage. It was also found that the surface resistivity varies for different grades of silicone material applied as coating, and the results are found to be consistent with the detector efficiency and noise rate measurements done with these RPCs.