Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
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<strong>Nuclear</strong> Sciences 59the closed-form expressions was made by comparing the potential and fields evaluated for a unittriangular element using ISLES library functions with that produced by numerical quadrature <strong>of</strong>high accuracy. A classic benchmark problem in electrostatics <strong>of</strong> estimating the capacitance <strong>of</strong> aunit square plate with unit volt was solved and compared with accurate results available in theliterature. The variation <strong>of</strong> the charge density close to the corner <strong>of</strong> the plate with various degrees<strong>of</strong> discretization was examined and found to be smooth and accurate (difficult to be estimatedusing BEM).Supratik Mukhopadhyay, Nayana MajumdarINO2.5.1.3 Simulation <strong>of</strong> electrostatic field configuration <strong>of</strong> cylindrical proportionalcounterFEM and BEM are two numerical methods used for electrostatic field simulation <strong>of</strong> gaseous detectors.FEM can treat any arbitrary geometry endowed with dielectrics, but suffers from severallimitations like interpolation <strong>of</strong> potential with low order polynomial at non-nodal points and estimation<strong>of</strong> the field by numerical differentiation <strong>of</strong> potential which is inadequate in the regionswith steep field gradient. BEM avoids such errors since it employs Greens function to estimate thepotential and field anywhere inside the detector. A solver based on the zero-th order BEM wherethe charge distributions were assumed to be uniform and equivalent to point charges located at thecentroid <strong>of</strong> the boundary elements was developed. The results using the solver was found to agreesatisfactorily with analytical values available for the 2D version <strong>of</strong> the problem. Deviations fromthe analytic values due to 3D effects <strong>of</strong> a realistic finite detector for a wide range <strong>of</strong> aspect ratio(ratio <strong>of</strong> length to radius) were studied.Supratik Mukhopadhyay, Nayana MajumdarINO2.5.1.4 Simulation <strong>of</strong> electrostatic configuration <strong>of</strong> wire chambersA detailed study <strong>of</strong> 3D electrostatic field in several wire chambers like Iarocci Tube and MultiWireProportional Chamber (MWPC) were carried out invoking real life geometry using theneBEM solver providing precise estimates which were different from the available analytical values(calculated with simplified 2D geometry) when the finite bound <strong>of</strong> the geometry was concerned.Significant amount <strong>of</strong> deviation was observed in the avalanche region (close to the anode wire) incase <strong>of</strong> Iarocci Tube. It was the edge effect which changed the field near the anode wires placednear the edges in the MWPC. In fact, the study made clear why the use <strong>of</strong> field shaping wires arenecessary in a MWPC. Effects <strong>of</strong> wire modeling on the precision <strong>of</strong> result was also studied.Nayana Majumdar, Supratik MukhopadhyayINO2.5.1.5 Simulation <strong>of</strong> electrostatic configuration <strong>of</strong> RPCThe presence <strong>of</strong> closely spaced surfaces in gaseous detectors with multiple dielectrics like ResistivePlate Chamber (RPC) is known to give rise to numerical complexities in conventional BEM calculation.The efficacy <strong>of</strong> the neBEM solver was validated by comparing its results for a multiple
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