FABRICATION OF RPC DETECTOR AND ITS FRONT-END ELECTRONICS USING NINO ASIC CHIP FOR INO-ICAL PROJECT

Abstract

INO is an Indian-based Neutrino Observatory project which is a multi-Institutional Collaboration for setting up a magnetized Iron Calorimeter (ICAL) detector to detect atmospheric neutrino and study their properties. It is a world class underground laboratory for high energy experimental and nuclear physics research in India. The primary goal of INO is to study Neutrino because they are the fundamental particles having little mass but were expected to be massless in standard of particle physics. Today, determination of neutrino masses and mixing parameters is one the most challenging open problem in physics. So, ICAL detector is going to be designed to address this key open problem in a unique way. The Resistive Plate Chamber (RPC) detectors (with a single gas gap) have been chosen as the active detector elements for the magnetized iron calorimeter (ICAL) detector at INO, due to their excellent efficiency, position (mm) & timing (ns) characteristics and suitability for large detector coverage. I have done the fabrication and preliminary characterization including efficiency, counting rate, leakage current and time resolution of RPC detectors (dimension 30 cm × 30 cm). I took two glasses of 2 mm thickness coated with a conductive layer of graphite, are used as the external electrodes. The pickup panel consists of honeycomb panels with copper strips of width 2 cm. The gas gaps are sealed by gluing side spacers between the outermost electrodes. The RPCs are being tested in avalanche mode with a gas mixture of Freon (R134a-95.15%), Isobutane ( -4.51%), (0.34%) with a flow rate of 5 SCCM. Three scintillator paddles of width 2 cm in coincidence mode has been used for the trigger. The signals from the pickup strips are amplified with the NINO ASIC chip and then taken with coincidence with the trigger. An ultra-fast front-end preamplifier-discriminator chip NINO has been developed for use in the ALICE Time-Of-Flight detector. The chip has 8 channels and each channel is designed with an amplifier with less than 1 ns peaking time, a discriminator with a minimum detection threshold of 10fC and an output stage. The output pulse has minimum time jitter (less than 25ps) on the front edge, and the pulse width is dependent of the input signal charge. Each channel in NINO chip takes the differential signal from the pickup strips as input, and amplifies them in a four stage cascade amplifier. The study on the detector performance with varying HV and at different concentrations of the gas mixture components will be presented in detail.