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N. Majumdar

Publications and source records attributed to N. Majumdar.

At least 19 recordsLinked to original sources
arXiv2022

Quality Control of Mass-Produced GEM Detectors for the CMS GE1/1 Muon Upgrade

The series of upgrades to the Large Hadron Collider, culminating in the High Luminosity Large Hadron Collider, will enable a significant expansion of the physics program of the CMS experiment. However, the accelerator upgrades will also make the experimental conditions more challenging, with implications for detector operations, triggering, and data analysis. The luminosity of the proton-proton collisions is expected to exceed $2-3\times10^{34}$~cm$^{-2}$s$^{-1}$ for Run 3 (starting in 2022), and it will be at least $5\times10^{34}$~cm$^{-2}$s$^{-1}$ when the High Luminosity Large Hadron Collider is completed for Run 4. These conditions will affect muon triggering, identification, and measurement, which are critical capabilities of the experiment. To address these challenges, additional muon detectors are being installed in the CMS endcaps, based on Gas Electron Multiplier technology. For this purpose, 161 large triple-Gas Electron Multiplier detectors have been constructed and tested. Installation of these devices began in 2019 with the GE1/1 station and will be followed by two additional stations, GE2/1 and ME0, to be installed in 2023 and 2026, respectively. The assembly and quality control of the GE1/1 detectors were distributed across several production sites around the world. We motivate and discuss the quality control procedures that were developed to standardize the performance of the detectors, and we present the final results of the production. Out of 161 detectors produced, 156 detectors passed all tests, and 144 detectors are now installed in the CMS experiment. The various visual inspections, gas tightness tests, intrinsic noise rate characterizations, and effective gas gain and response uniformity tests allowed the project to achieve this high success rate.

physics.ins-det↗
arXiv2021

Performance of a Triple-GEM Demonstrator in $pp$ Collisions at the CMS Detector

After the Phase-2 high-luminosity upgrade to the Large Hadron Collider (LHC), the collision rate and therefore the background rate will significantly increase, particularly in the high $η$ region. To improve both the tracking and triggering of muons, the Compact Muon Solenoid (CMS) Collaboration plans to install triple-layer Gas Electron Multiplier (GEM) detectors in the CMS muon endcaps. Demonstrator GEM detectors were installed in CMS during 2017 to gain operational experience and perform a preliminary investigation of detector performance. We present the results of triple-GEM detector performance studies performed in situ during normal CMS and LHC operations in 2018. The distribution of cluster size and the efficiency to reconstruct high $p_T$ muons in proton--proton collisions are presented as well as the measurement of the environmental background rate to produce hits in the GEM detector.

physics.ins-det↗
arXiv2021

Modeling the triple-GEM detector response to background particles for the CMS Experiment

An estimate of environmental background hit rate on triple-GEM chambers is performed using Monte Carlo (MC) simulation and compared to data taken by test chambers installed in the CMS experiment (GE1/1) during Run-2 at the Large Hadron Collider (LHC). The hit rate is measured using data collected with proton-proton collisions at 13 TeV and a luminosity of 1.5$\times10^{34}$ cm$^{-2}$ s$^{-1}$. The simulation framework uses a combination of the FLUKA and Geant4 packages to obtain the hit rate. FLUKA provides the radiation environment around the GE1/1 chambers, which is comprised of the particle flux with momentum direction and energy spectra ranging from $10^{-11}$ to $10^{4}$ MeV for neutrons, $10^{-3}$ to $10^{4}$ MeV for $γ$'s, $10^{-2}$ to $10^{4}$ MeV for $e^{\pm}$, and $10^{-1}$ to $10^{4}$ MeV for charged hadrons. Geant4 provides an estimate of detector response (sensitivity) based on an accurate description of detector geometry, material composition and interaction of particles with the various detector layers. The MC simulated hit rate is estimated as a function of the perpendicular distance from the beam line and agrees with data within the assigned uncertainties of 10-14.5%. This simulation framework can be used to obtain a reliable estimate of background rates expected at the High Luminosity LHC.

physics.ins-det↗
arXiv2020

Interstrip Capacitances of the Readout Board used in Large Triple-GEM Detectors for the CMS Muon Upgrade

We present analytical calculations, Finite Element Analysis modeling, and physical measurements of the interstrip capacitances for different potential strip geometries and dimensions of the readout boards for the GE2/1 triple-Gas Electron Multiplier detector in the CMS muon system upgrade. The main goal of the study is to find configurations that minimize the interstrip capacitances and consequently maximize the signal-to-noise ratio for the detector. We find agreement at the 1.5--4.8% level between the two methods of calculations and on the average at the 17% level between calculations and measurements. A configuration with halved strip lengths and doubled strip widths results in a measured 27--29% reduction over the original configuration while leaving the total number of strips unchanged. We have now adopted this design modification for all eight module types of the GE2/1 detector and will produce the final detector with this new strip design.

physics.ins-det↗
arXiv2016

Effect of water vapor on the performance of glass RPCs in avalanche mode operation

We studied the effect of water vapor on the performance of glass Resistive Plate Chambers (RPCs) in the avalanche mode operation. Controlled and calibrated amount of water vapor was added to the RPC gas mixture that has C$_2$H$_2$F$_4$ as the major component. The deterioration in the performance of RPC was observed while operating with wet gas and recovered after switching to standard gas.

physics.ins-det↗
arXiv2015

A novel application of Fiber Bragg Grating (FBG) sensors in MPGD

We present a novel application of Fiber Bragg Grating (FBG) sensors in the construction and characterisation of Micro Pattern Gaseous Detector (MPGD), with particular attention to the realisation of the largest triple (Gas electron Multiplier) GEM chambers so far operated, the GE1/1 chambers of the CMS experiment at LHC. The GE1/1 CMS project consists of 144 GEM chambers of about 0.5 m2 active area each, employing three GEM foils per chamber, to be installed in the forward region of the CMS endcap during the long shutdown of LHC in 2108-2019. The large active area of each GE1/1 chamber consists of GEM foils that are mechanically stretched in order to secure their flatness and the consequent uniform performance of the GE1/1 chamber across its whole active surface. So far FBGs have been used in high energy physics mainly as high precision positioning and re-positioning sensors and as low cost, easy to mount, low space consuming temperature sensors. FBGs are also commonly used for very precise strain measurements in material studies. In this work we present a novel use of FBGs as flatness and mechanical tensioning sensors applied to the wide GEM foils of the GE1/1 chambers. A network of FBG sensors have been used to determine the optimal mechanical tension applied and to characterise the mechanical tension that should be applied to the foils. We discuss the results of the test done on a full-sized GE1/1 final prototype, the studies done to fully characterise the GEM material, how this information was used to define a standard assembly procedure and possible future developments.

physics.ins-det↗
arXiv2014

Performance of a Large-Area GEM Detector Prototype for the Upgrade of the CMS Muon Endcap System

Gas Electron Multiplier (GEM) technology is being considered for the forward muon upgrade of the CMS experiment in Phase 2 of the CERN LHC. Its first implementation is planned for the GE1/1 system in the $1.5 < \midη\mid < 2.2$ region of the muon endcap mainly to control muon level-1 trigger rates after the second long LHC shutdown. A GE1/1 triple-GEM detector is read out by 3,072 radial strips with 455 $μ$rad pitch arranged in eight $η$-sectors. We assembled a full-size GE1/1 prototype of 1m length at Florida Tech and tested it in 20-120 GeV hadron beams at Fermilab using Ar/CO$_{2}$ 70:30 and the RD51 scalable readout system. Four small GEM detectors with 2-D readout and an average measured azimuthal resolution of 36 $μ$rad provided precise reference tracks. Construction of this largest GEM detector built to-date is described. Strip cluster parameters, detection efficiency, and spatial resolution are studied with position and high voltage scans. The plateau detection efficiency is [97.1 $\pm$ 0.2 (stat)]\%. The azimuthal resolution is found to be [123.5 $\pm$ 1.6 (stat)] $μ$rad when operating in the center of the efficiency plateau and using full pulse height information. The resolution can be slightly improved by $\sim$ 10 $μ$rad when correcting for the bias due to discrete readout strips. The CMS upgrade design calls for readout electronics with binary hit output. When strip clusters are formed correspondingly without charge-weighting and with fixed hit thresholds, a position resolution of [136.8 $\pm$ 2.5 stat] $μ$rad is measured, consistent with the expected resolution of strip-pitch/$\sqrt{12}$ = 131.3 $μ$rad. Other $η$-sectors of the detector show similar response and performance.

physics.ins-det↗
arXiv2012

Performances of silicone coated high resistive bakelite RPC

Performances of several single gap (gas gap 2 mm) prototype Resistive Plate Chambers (RPC) made of high resistive (ρ \sim 1010 - 1012 Ω cm) bakelite, commercially available in India have been studied in recent times. To make the inner electrode surfaces smooth, a thin coating of silicone has been applied. An efficiency > 90% and time resolution \sim 2 ns (FWHM) have been obtained for both the streamer and the avalanche mode. The induced charge distributions of those silicone coated RPC are studied and the results are presented. A numerical study on the effect of surface roughness of the resistive electrodes on the electric field of the device has been carried out using Garfield-neBEM code. A few results for a simplified model representing surface roughness, measured using a surface profilometer for the bakelite surfaces, have also been presented.

physics.ins-det↗
arXiv2007

Fast and Precise 3D Computation of Capacitance of Parallel Narrow Beam MEMS Structures

Efficient design and performance of electrically actuated MEMS devices necessitate accurate estimation of electrostatic forces on the MEMS structures. This in turn requires thorough study of the capacitance of the structures and finally the charge density distribution on the various surfaces of a device. In this work, nearly exact BEM solutions have been provided in order to estimate these properties of a parallel narrow beam structure found in MEMS devices. The effect of three-dimensionality, which is an important aspect for these structures, and associated fringe fields have been studied in detail. A reasonably large parameter space has been covered in order to follow the variation of capacitance with various geometric factors. The present results have been compared with those obtained using empirical parametrized expressions keeping in view the requirement of the speed of computation. The limitations of the empirical expressions have been pointed out and possible approaches of their improvement have been discussed.

physics.comp-ph↗
arXiv2007

Computation of Electrostatic and Gravitational Sag in MultiWire Chambers

A numerical method of determining the wire sag in a multiwire proportional chamber used in RICH (ALICE) by solving the second order differential equation which governs the wire stability has been presented. The three point Finite Difference Method (FDM) has generated a tridiagonal matrix equation relating the deflection of wire segments to the force acting on it. The precise estimates of electrostatic force has been obtained from accurate field computation using a nearly exact Boundary Element Method (neBEM) solver.

physics.ins-det↗
arXiv2007

Simulation of Pickup Signal in a Resistive Plate Chamber

The signal induced by an electron on a pickup strip has been calculated in a RPC used in INO calorimeter following Ramo's theorem. An accurate estimation of weighting field has been obtained using a nearly exact Boundary Element Method (neBEM) solver while the electron velocity from the real field values. The calculation has shown a growth and subsequent fall of pickup signal with duration about 90ps.

physics.ins-det↗
arXiv2007

Estimation of Weighting Potential for a TPC

In this work, we have computed the three dimensional weighting potential, field and pad response function (PRF) of typical time projection chambers (TPC) using a recently formulated and developed boundary element method solver, namely, the nearly exact BEM solver. A realistic geometry of the device is found to have significant influence on the estimation of signal generation.

physics.ins-det↗
arXiv2007

3D Simulation of New Generation Gas Detectors

Simulation of new generation gas detectors is rendered complicated due to the non-trivial nature of the electric field and simultaneous presence of several length-scales. Computation of the electrostatic field, however, is extremely important since streamers in gas volume and streamers across the dielectric surfaces are known to cause serious damage to Micro Pattern Gas Detectors (MPGD)and are the main factors in limiting their gain. In this paper, we present the use of a nearly exact Boundary Element Method (neBEM) solver that overcomes most of the limitations of FEM packages and is capable of producing accurate results.

physics.ins-det↗
arXiv2006

Factors Affecting the Precision of Electrostatic Computation of 3D MEMS Structures

Micro-Electro-Mechanical Systems (MEMS) normally have fixed or moving structures (plates or array of thin beams) with cross-sections of the order of microns and lengths of the order of tens or hundreds of microns. Electrostatic forces play a very major role in maneuvering these devices, and hence, a thorough understanding of the electrostatic properties of these structures is of critical importance. Recently, a nearly exact boundary element method (neBEM) solver has been developed and used to solve difficult problems related to electrostatics of various devices. Because of the exact foundation expressions, this solver has been found to be very accurate while solving critical problems which normally necessitate special formulations involving elegant, but difficult mathematics. In this work, we investigate the effects of various possible approximations on the 3D electrostatic solutions obtained for MEMS structures. In particular, we investigate the effects of discretization, omission of surfaces with small amount of charge accumulation on the final results such as the charge distribution on various surfaces or capacitance of a given MEMS structure.

physics.comp-ph↗
arXiv2006

Use of the neBEM solver to Compute the 3D Electrostatic Properties of Comb Drives

Micro-Electro-Mechanical Systems (MEMS) comb drives are used for both as sensors and actuators. As a result, they have been considered to be very important in MEMS technology and has been under intense study for last few years. The actuation and the sensitivity are both dependent in a major way on the electrostatic configuration of the comb structure. As a result, accurate estimation of the electrostatic configuration of comb drives is crucial in both design and interpretation phases. The nearly exact Boundary Element Method (neBEM) solver has been developed recently and used successfully to solve difficult problems related to electrostatics. This solver uses exact analytic expression for computing the influence of singularity distributions instead of adopting the conventional and convenient approximation of nodal concentration of charges. Due to the exact foundation expressions, the solver has been found to be exceptionally accurate in the complete physical domain, including the near field. In this work, we explore the possibility of using the neBEM solver to solve 3D electrostatic problems related to comb drives. In particular, we investigate the relationship between the accuracy achieved and the computational expenses incurred for a realistic comb drive geometry. In the process, we estimate the charge density distribution, potential distribution and the capacitance of the comb structure. The study has led us to the conclusion that the neBEM solver can yield very accurate estimates of all the properties of interest at a reasonable computational expenditure.

physics.comp-ph↗
arXiv2006

Simulation of Three Dimensional Electrostatic Field Configuration in Wire Chambers : A Novel Approach

Three dimensional field configuration has been simulated for a simple wire chamber consisting of one anode wire stretched along the axis of a grounded square cathode tube by solving numerically the boundary integral equation of the first kind. A closed form expression of potential due to charge distributed over flat rectangular surface has been invoked in the solver using Green's function formalism leading to a nearly exact computation of electrostatic field. The solver has been employed to study the effect of several geometrical attributes such as the aspect ratio ($λ= \frac{l}{d}$, defined as the ratio of the length $l$ of the tube to its width $d$) and the wire modeling on the field configuration. Detailed calculation has revealed that the field values deviate from the analytic estimates significantly when the $λ$ is reduced to 2 or below. The solver has demonstrated the effect of wire modeling on the accuracy of the estimated near-field values in the amplification region. The thin wire results can be reproduced by the polygon model incorporating a modest number of surfaces ($\geq 32$) in the calculation with an accuracy of more than 99%. The smoothness in the three dimensional field calculation in comparison to fluctuations produced by other methods has been observed.

physics.ins-det↗
arXiv2006

Computation of Nearly Exact 3D Electrostatic Field in Gas Ionization Detectors

The three-dimensional electrostatic field configuration in gas ionization detectors has been simulated using an efficient and precise nearly exact boundary element method (NEBEM) solver set up to solve an integral equation of the first kind. This recently proposed formulation of BEM and the resulting solver use exact analytic integral of Green function to compute the electrostatic potential for charge distribution on flat surfaces satisfying Poisson's equation. As a result, extremely precise results have been obtained despite the use of relatively coarse discretization leading to successful validation against analytical results available for two-dimensional MWPCs. Significant three dimensional effects have been observed in the electrostatic field configuration and also on the force experienced by the anode wires of MWPCs. In order to illustrate the applicability of the NEBEM solver for detector geometries having multiple dielectrics and degenerate surfaces, it has been validated against available FEM and BEM numerical solutions for similar geometries.

physics.ins-det↗