R.R. Shinde

Effect of ambient pressure variation on closed loop gas system for India based Neutrino Observatory (INO)

Pilot unit of a closed loop gas mixing and distribution system for the INO project was designed and is being operated with 1.8meters × 1.9meters RPCs for about two years. A number of studies on controlling the flow and optimisation of the gas mixture through the RPC stack were carried out during this period. The gas system essentially measures and attempts to maintain absolute pressure inside the RPC gas volume. During typical Mumbai monsoon seasons, the barometric pressure changes rather rapidly, due to which the gas system fails to maintain the set differential pressure between the ambience and the RPC gas volume. As the safety bubblers on the RPC gas input lines are set to work on fixed pressure differentials, the ambient pressure changes lead to either venting out and thus wasting gas through safety bubblers or over pressuring the RPCs gas volume and thus degrading its performance. The above problem also leads to gas mixture contamination through minute leaks in gas gap. The problem stated above was solved by including the ambient barometric pressure as an input parameter in the closed loop. Using this, it is now possible to maintain any set differential pressure between the ambience and RPC gas volumes between 0 to 20mm of water column, thus always ensuring a positive pressure inside the RPC gas volume with respect to the ambience. This has resulted in improved performance of the gas system by maintaining the constant gas flow and reducing the gas toping up frequency. In this paper, we will highlight the design features and improvements of the closed loop gas system. We will present some of the performance studies and considerations for scaling up the system to be used with the engineering module and then followed by Iron Calorimeter detector (ICAL), which is designed to deploy about 30,000 RPCs of 1.8meters × 1.9 meters in area.

A compact cosmic muon veto detector and possible use with the Iron Calorimeter detector for neutrinos

The motivation for a cosmic muon veto (CMV) detector is to explore the possibility of locating the proposed large Iron Calorimeter (ICAL) detector at the India based Neutrino Observatory (INO) at a shallow depth. An initial effort in that direction, through the assembly and testing of a

Development of a Resistive Plate Chamber with heat strengthened glass

\sim

Design validation and performance of closed loop gas recirculation system

1 m

Glass RPC detector R&D for a mega neutrino detector

\times

Development of glass resistive plate chambers for INO experiment

1 m

Development of 2 m×2 m size glass RPCs for INO

\times

VME-based data acquisition system for the India-based Neutrino Observatory prototype detector

0.3 m plastic scintillator based detector, is described. The plan for making a CMV detector for a smaller prototype mini-ICAL is also outlined.

Cosmic ray test of INO RPC stack

The Iron Calorimeter (ICAL) detector at INO cavern will be made of 50 kTon of magnetized steel layers, tiled with 4 m \(\times \) 2 m \(\times \) 56 mm thick plates, alternating with layers of RPCs. The total number of \(2 \times 2\) m\(^2\) RPCs required will be about 29000. However, during the assembly of RPCs, handling the \(2 \times 2\) m\(^2\) normal float glass of thickness 3 mm is both difficult and risky and will be much easier to handle RPCs with toughened or tempered glass. This paper presents a comparison of the characteristics, such as noise rate, dark current, muon detection efficiency and time resolution, of normal and hardened glass RPCs.

Preliminary results from India-based Neutrino Observatory detector R&D programme

A pilot experimental set up of the India Based Neutrino Observatorys ICAL detector has been operational for the last 4 years at TIFR, Mumbai. Twelve glass RPC detectors of size 2 × 2 m2, with a gas gap of 2 mm are under test in a closed loop gas recirculation system. These RPCs are continuously purged individually, with a gas mixture of R134a (C2H2F4), isobutane (iC4H10) and sulphur hexafluoride (SF6) at a steady rate of 360 ml/h to maintain about one volume change a day. To economize gas mixture consumption and to reduce the effluents from being released into the atmosphere, a closed loop system has been designed, fabricated and installed at TIFR. The pressure and flow rate in the loop is controlled by mass flow controllers and pressure transmitters. The performance and integrity of RPCs in the pilot experimental set up is being monitored to assess the effect of periodic fluctuation and transients in atmospheric pressure and temperature, room pressure variation, flow pulsations, uniformity of gas distribution and power failures. The capability of closed loop gas recirculation system to respond to these changes is also studied. The conclusions from the above experiment are presented. The validations of the first design considerations and subsequent modifications have provided improved guidelines for the future design of the engineering module gas system.