arXiv subjects

Nayana Majumdar

Publications and source records attributed to Nayana Majumdar.

46 records · Page 3Linked to original sources

arXiv2016

Effect of plate roughness on the field near RPC plates

The inner surfaces of the electrodes encompassing the gas volume of a Resistive Plate Chamber (RPC) have been found to exhibit asperities with, grossly, three kinds of features. The desired uniform electric field within the gas volume of RPC is expected to be affected due to the presence of these asperities, which will eventually affect the final response from the detector. In this work, an attempt has been made to model the highly complex roughness of the electrode surfaces and compute its effect on the electrostatic field within RPC gas chamber. The calculations have been performed numerically using Finite Element Method (FEM) and Boundary Element Method (BEM) and the two methods have been compared in this context.

physics.ins-det↗

arXiv2016

Numerical Studies on Time Resolution of Micro-Pattern Gaseous Detectors

The Micro-Pattern Gaseous Detectors offer excellent spatial and temporal resolution in harsh radiation environments of high-luminosity colliders. In this work, an attempt has been made to establish an algorithm for estimating the time resolution of different MPGDs. It has been estimated numerically on the basis of two aspects, statistics and distribution of primary electrons and their diffusion in gas medium, while ignoring their multiplication. The effect of detector design parameters, field configuration and the composition of gas mixture on the resolution have also been investigated. Finally, a modification in the numerical approach considering the threshold limit of detecting the signal has been done and tested for the RPC detector for its future implementation in case of MPGDs.

physics.ins-det↗

arXiv2016

The effect of spacers on the performance of Micromegas detectors: a numerical investigation

Micromegas detector is considered to be a promising candidate for a large variety of high-rate experiments. Micromegas of various geometries have already been established as appropriate for these experiments for their performances in terms of gas gain uniformity, energy and space point resolution, and their capability to efficiently pave large read-out surfaces with minimum dead zone. The present work investigates the effect of spacers on different detector characteristics of Micromegas detectors having various amplification gaps and mesh hole pitches. Numerical simulation has been used as a tool of exploration to evaluate the effect of such dielectric material on detector performance. Some of the important and fundamental characteristics such as electron transparency, gain and signal of the Micromegas detector have been estimated.

physics.ins-det↗

arXiv2016

Investigation of Ion Backflow in Bulk Micromegas Detectors

The operation of gas detectors is often limited by secondary effects, originating from avalanche-induced photons and ions. Ion backflow is one of the effects limiting the operation of a gas detector at high flux, by giving rise to space charge which disturbs the electric field locally. For the Micromegas detector, a large fraction of the secondary positive ions created in the avalanche can be stopped at the micro-mesh. The present work involves measurements of the ion backflow fraction (using an experimental setup comprising of two drift planes) in bulk Micromegas detectors as a function of detector design parameters. These measured characteristics have also been compared in detail to numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed. Further, the effect of using a second micro-mesh on ion backflow and other parameters has been studied numerically.

physics.ins-det↗

arXiv2016

Performance Studies of Bulk Micromegas of Different Design Parameters

The present work involves the comparison of various bulk Micromegas detectors having different design parameters. Six detectors with amplification gaps of $64,~128,~192,~220 ~μ\mathrm{m}$ and mesh hole pitch of $63,~78 ~μ\mathrm{m}$ were tested at room temperature and normal gas pressure. Two setups were built to evaluate the effect of the variation of the amplification gap and mesh hole pitch on different detector characteristics. The gain, energy resolution and electron transmission of these Micromegas detectors were measured in Argon-Isobutane (90:10) gas mixture while the measurements of the ion backflow were carried out in P10 gas. These measured characteristics have been compared in detail to the numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed.

physics.ins-det↗

arXiv2016

A Time Projection Chamber with GEM-Based Readout

For the International Large Detector concept at the planned International Linear Collider, the use of time projection chambers (TPC) with micro-pattern gas detector readout as the main tracking detector is investigated. In this paper, results from a prototype TPC, placed in a 1 T solenoidal field and read out with three independent GEM-based readout modules, are reported. The TPC was exposed to a 6 GeV electron beam at the DESY II synchrotron. The efficiency for reconstructing hits, the measurement of the drift velocity, the space point resolution and the control of field inhomogeneities are presented.

physics.ins-det↗

arXiv2013

Comparison of Bulk Micromegas with Different Amplification Gaps

The bulk Micromegas detector is considered to be a promising candidate for building TPCs for several future experiments including the projected linear collider. The standard bulk with a spacing of 128 micron has already established itself as a good choice for its performances in terms of gas gain uniformity, energy and space point resolution, and its capability to efficiently pave large readout surfaces with minimum dead zone. The present work involves the comparison of this standard bulk with a relatively less used bulk Micromegas detector having a larger amplification gap of 192 micron. Detector gain, energy resolution and electron transparency of these Micromegas have been measured under different conditions in various argon based gas mixtures to evaluate their performance. These measured characteristics have also been compared in detail to numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed. Further, we have carried out another numerical study to determine the effect of dielectric spacers on different detector features. A comprehensive comparison of the two detectors has been presented and analyzed in this work.

physics.ins-det↗

arXiv2013

A Comparative Numerical Study on GEM, MHSP and MSGC

In this work, we have tried to develop a detailed understanding of the physical processes occurring in those variants of Micro Pattern Gas Detectors (MPGDs) that share micro hole and micro strip geometry, like GEM, MHSP and MSGC etc. Some of the important and fundamental characteristics of these detectors such as gain, transparency, efficiency and their operational dependence on different device parameters have been estimated following detailed numerical simulation of the detector dynamics. We have used a relatively new simulation framework developed especially for the MPGDs that combines packages such as GARFIELD, neBEM, MAGBOLTZ and HEED. The results compare closely with the available experimental data. This suggests the efficacy of the framework to model the intricacies of these micro-structured detectors in addition to providing insight into their inherent complex dynamical processes.

physics.ins-det↗

arXiv2008

A Study of Three Dimensional Edge and Corner Problems using the neBEM Solver

The previously reported neBEM solver has been used to solve electrostatic problems having three-dimensional edges and corners in the physical domain. Both rectangular and triangular elements have been used to discretize the geometries under study. In order to maintain very high level of precision, a library of C functions yielding exact values of potential and flux influences due to uniform surface distribution of singularities on flat triangular and rectangular elements has been developed and used. Here we present the exact expressions proposed for computing the influence of uniform singularity distributions on triangular elements and illustrate their accuracy. We then consider several problems of electrostatics containing edges and singularities of various orders including plates and cubes, and L-shaped conductors. We have tried to show that using the approach proposed in the earlier paper on neBEM and its present enhanced (through the inclusion of triangular elements) form, it is possible to obtain accurate estimates of integral features such as the capacitance of a given conductor and detailed ones such as the charge density distribution at the edges / corners without taking resort to any new or special formulation. Results obtained using neBEM have been compared extensively with both existing analytical and numerical results. The comparisons illustrate the accuracy, flexibility and robustness of the new approach quite comprehensively.

physics.comp-ph↗

arXiv2007

Use of Triangular Elements for Nearly Exact BEM Solutions

A library of C functions yielding exact solutions of potential and flux influences due to uniform surface distribution of singularities on flat triangular and rectangular elements has been developed. This library, ISLES, has been used to develop the neBEM solver that is both precise and fast in solving a wide range of problems of scientific and technological interest. Here we present the exact expressions proposed for computing the influence of uniform singularity distributions on triangular elements and illustrate their accuracy. We also present a study concerning the time taken to evaluate these long and complicated expressions \textit{vis a vis} that spent in carrying out simple quadratures. Finally, we solve a classic benchmark problem in electrostatics, namely, estimation of the capacitance of a unit square plate raised to unit volt. For this problem, we present the estimated values of capacitance and compare them successfully with some of the most accurate results available in the literature. In addition, we present the variation of the charge density close to the corner of the plate for various degrees of discretization. The variations are found to be smooth and converging. This is in clear contrast to the criticism commonly leveled against usual BEM solvers.

math.NA↗