Abhik Jash

Invited review: Physics potential of the ICAL detector at the India-based Neutrino Observatory (INO)

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.

Simulation of efficiency and time resolution of resistive plate chambers and comparison with experimental data

The India based Neutrino Observatory (INO) collaboration is planning to build a 50 kton magnetized Iron Calorimeter (ICAL) detector to study neutrino oscillations and measure their associated parameters. ICAL will use 28,800 glass Resistive Plate Chambers (RPCs) of 2 m?2 m in size as its active detector elements. These RPCs will be operated in the avalanche mode. As a part of the detector R&D to develop the RPCs required for this detector, we made a comparative study of the effect of Sulphur Hexafluoride (SF6) in the gas mixture on the induced charge using simulation and experimental data in our earlier paper [1]. In this paper, we extend our studies to efficiency and time resolution of the RPC using simulation and experimental data. Several software tools have been used to carry out the simulation. We have calculated the primary interaction parameters using HEED and Geant4. The electron transport parameters have been computed using MAGBOLTZ. We have used nearly exact Boundary Element Method (neBEM) and COMSOL Multiphysics, a Finite Element Method package for calculating the weighting field and the electric field.

Numerical studies on electrostatic field configuration of Resistive Plate Chambers for the INO-ICAL experiment

As a part of detailed optimization studies on Resistive Plate Chambers (RPC) to be used in INO-ICAL experiment, the effect of geometrical artifacts like edge, corner, spacers on the device response should be investigated thoroughly. In this context, the electrostatic field within an RPC has been computed following Finite Element Method and Boundary Element Method to study the effect of these artifacts on the field map. The weighting field distribution for the given geometry has also been evaluated which is necessary for simulating the device signal. A unified model to calculate both physical and weighting field within RPC has been proposed and tested for its validity.

Numerical study on the effect of design parameters and spacers on RPC signal and timing properties

Numerical calculations have been performed to understand the reason for the observed non-uniform response of a Resistive Plate Chamber (RPC) in a few critical regions such as near edge spacers and corners of the device. In this context, the signal from a RPC due to the passage of muons through different regions has been computed. Also, a simulation of RPC timing properties is presented along with the effect of the applied field, gas mixture and geometrical components.

Qualification of Eco-Friendly Gas Mixture for Avalanche Mode Operation of RPC

The gas mixture to be used in the RPCs of INO-ICAL experiment is a mixture of R-134a, isobutane and \(\text {SF}_{6}\). Owing to huge Global Warming Potential of this mixture (GWP 1403), this needs to be substituted with an eco-friendly gas mixture without compromising the performance of ICAL. In this work, we propose to study the qualification of a mixture of argon and \(\text {CO}_{2}\) for avalanche mode operation of RPC, which has a very low GWP (\({<}1\)). To estimate the streamer probability of the new gas mixture at different operating voltages, the electronic charge produced in RPC signal has been simulated using two numerical methods.

Numerical Investigation on RPC Time Response

In the proposed Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO), the position and timing information of a passing muon will be detected by the Resistive Plate Chambers (RPC) stacked in 150 layers, interspersed alternately with iron plates. The present work involves a numerical study to understand the timing response of RPC which may be useful in optimizing and interpreting the ICAL performance. In this context, the timing properties of a Bakelite RPC has been simulated along with their dependence on the geometrical components and operating conditions.

Studies on Reconstruction Algorithms for Material Imaging with MST

In case of Muon Scattering Tomography (MST), one of the basic algorithms used for image reconstruction is the Point Of Closest Approach (POCA) algorithm. Here, a preliminary work is presented on simulation studies for the efficacy test of POCA algorithm performed by comparing it with a calculation done by GEANT4. The inelastic Coulomb scattering vertices for interactions of muons and atomic nuclei are determined from GEANT4 simulations. On the other hand, point of the POCA algorithm is calculated from the incoming and outgoing tracks of the muon. Distance between the point found using POCA algorithm and mean point of scattering heads is calculated for each event. Smallness of this distance attests the competence of the algorithm.

GEANT4 Simulation for Imaging of High-Z Materials Using Cosmic Ray Muons

High-energy muons generated from cosmic ray particle showers have been found to exhibit properties suitable for imaging the interior of large structures due to their high penetrating power. Based on absorption or scattering of the muons in the target object, a technique for producing three-dimensional image of the object, known as Muon Tomography, has been widely in practice for several decades for various applications in the fields of geology, industry, homeland security etc. In the present work, we attempt to produce numerically the shadows of different materials on detector planes placing it under muon shower using GEANT4 simulation framework. Cosmic ray muons of varying energy (10 MeV to 10 GeV) and of typical flux (1 muon/m\(^{2}\)/s) have been emulated using Monte-Carlo technique from a plane placed above the material under inspection. A cubical box of different materials like Al, Fe, Pb, Ag has been placed symmetrically under the particle generation plane between two layers of detection plane. The hit positions on the detectors have been plotted to study the image pattern produced for different materials individually.

Effect of Electric Field and Gas Mixture on RPC Time Resolution

A large number of Resistive Plate Chamber will be used in the ICAL detector set-up in the proposed INO facility. The timing response from RPCs will govern the accuracy of ICAL in distinguishing the up-going muon tracks from the down-going ones by recording the time of passage of the muons through the RPCs. The timing performance of a bakelite RPC has been studied both experimentally and numerically to understand the effect of different operating conditions, like applied voltage and used gas mixture, on the timing properties. This can lead us to judge the suitability of bakelite RPC for application in ICAL set-up which is planned to be equipped with glass RPCs at present.

Effect of Geometrical Artifacts on the Response of INO-ICAL RPC

As a part of detailed optimization studies on RPCs to be used in INO-ICAL experiment, the effect of geometrical artifacts on the device response has been investigated. In this context, the electrostatic field within an RPC has been studied. The computation of the field configuration has been done following the Finite Element Method and the Boundary Element Method. The model parameters have been adopted from a prototype of dimension 30 cm \(\times \) 30 cm. The weighting field distribution has also been studied which is necessary for simulating the device signal. A typical RPC signal has been calculated and compared to the measurement accomplished with the prototype.