[Paper Review] Optimisation and Characterisation of Glass RPC for India-based Neutrino Observatory Detectors

R. Kanishka, V. Bhatnagar+1 more|arXiv (Cornell University)|May 30, 2016

Particle Detector Development and Performance12 references3 citations

TL;DR

This paper optimizes and characterizes glass Resistive Plate Chambers (RPCs) for the India-based Neutrino Observatory's ICAL detector, evaluating Asahi and Saint Gobain glass electrodes against Modi glass through multi-parameter testing. It identifies Asahi and Saint Gobain as superior due to higher efficiency (>90%) and lower cross-talk (<30%) in avalanche mode with three-gas mixtures, ensuring long-term performance for 15–20 year operation.

ABSTRACT

The proposed magnetised Iron CALorimeter detector (ICAL) to be built in the India-based Neutrino Observatory (INO) laboratory aims to detect atmospheric muon neutrinos. In order to achieve improved physics results, the constituent components of the detector must be fully understood by proper characterisation and optimisation of various parameters. Resistive Plate Chambers (RPCs) are the active detector elements in the ICAL detector and can be made of glass or bakelite. The number of RPCs required for this detector are very large so a detailed study is necessary to establish the characterisation and optimisation of these RPCs. These detectors once installed will be taking data for 15-20 years. In this paper, we report the selection criteria of the glass electrodes procured from Indian manufacturers. Based on the factors that deteriorate the quality of glass the choice of electrode is made. The glass characterisation studies include UV-VIS transmission for optical properties, SEM, AFM for surface properties, WD-XRF, PIXE for determining the composition of glass samples and electrical properties. Based on these techniques a procedure is adopted to arrive at the best glass sample. We have done a second order check on the quality of the fabricated glass RPCs. In this regard, the efficiency and cross-talk of RPCs were measured. Results from Asahi and Saint Gobain glass RPCs came out to be the best.

Motivation & Objective

• To identify the optimal glass electrode material for long-term operation in the ICAL detector of the India-based Neutrino Observatory (INO).
• To ensure RPCs maintain high efficiency and low cross-talk over 15–20 years of continuous data-taking.
• To characterize and compare glass samples from Indian manufacturers (Asahi, Saint Gobain, Modi) based on physical, electrical, optical, and compositional properties.
• To validate the performance of fabricated RPCs using efficiency and cross-talk measurements under different gas mixtures and operating modes.
• To establish a standardized procedure for selecting high-quality glass electrodes to minimize aging and signal degradation in RPCs.

Proposed method

• Procured glass samples from Asahi, Saint Gobain, and Modi manufacturers for comparative analysis.
• Conducted UV-VIS transmission, SEM, AFM, WD-XRF, and PIXE to evaluate optical, surface, and elemental properties.
• Measured electrical resistivity and bulk resistivity to ensure values within the target range (10^10–10^12 Ω·cm).
• Fabricated 30 cm × 30 cm RPCs using selected glass electrodes and tested them in avalanche and streamer modes with two- and three-gas mixtures.
• Measured efficiency and cross-talk using cosmic ray triggers and strip alignment to assess signal crosstalk and detection performance.
• Used a second-order validation by comparing cross-talk and efficiency across different gas compositions and operating voltages.

Experimental results

Research questions

• RQ1 Which glass electrode material (Asahi, Saint Gobain, or Modi) exhibits the best combination of optical, electrical, and surface properties for long-term RPC operation?
• RQ2 How does the addition of SF6 and argon to the gas mixture affect RPC efficiency and cross-talk in avalanche and streamer modes?
• RQ3 What is the relationship between operating voltage and RPC efficiency, and does it plateau at a stable value for each glass type?
• RQ4 To what extent does glass quality influence cross-talk, and can it be mitigated by optimized gas composition?
• RQ5 Can a standardized selection procedure be established for glass electrodes based on multi-parameter characterization to ensure detector reliability?

Key findings

• Asahi and Saint Gobain glass electrodes demonstrated superior performance with efficiency exceeding 90% in avalanche mode using three-gas mixtures.
• Cross-talk was significantly reduced in Asahi and Saint Gobain RPCs (12–30%) compared to Modi glass (60%) when using three-gas mixtures.
• Efficiency plateaued above 90% at higher operating voltages, with reduced fluctuations when SF6 was added to the gas mixture.
• The two-gas avalanche mode showed higher efficiency fluctuations and increased cross-talk (84–87% efficiency, 84–87% cross-talk) compared to three-gas mixtures.
• Modi glass RPCs exhibited the highest cross-talk (60%) and lower efficiency (91%) in three-gas avalanche mode, indicating material quality issues.
• Saint Gobain and Asahi RPCs achieved consistent cross-talk values of 12% and 30% respectively in three-gas avalanche mode, confirming their suitability for long-term deployment.