Speaker
Prof.
Nayana Majumdar
(Saha Institute of Nuclear Physics)
Description
Experimental evidences indicate that the surface treatment of the electrodes with
silicone in Bakelite-RPC improves the detector peformance in a significant way
[S. Biswas et al., NIM A602 (2009) 749, NIM A604 (2009) 310]. Studies on the
morphological features of the Bakelite grades used for building the detectors
reveal the presence of surface asperities in these materials. Thus, a detailed
investigation becomes necessary to understand the role of non-planarity of the
Bakelite surface in affecting the detector performance. It is conceivable that
depending on their shape and height, these asperities which are predominantly
three dimensional, can distort the local electric field configuration which is
otherwise uniform in the parallel plate-like configuration of RPC and thus even
lead to local discharges inside the active volume.
A numerical simulation has been carried out to probe effects of surface asperities
on the field configuration of the detector and eventually its performance. The data
obtained from the measurments of surface profiles of Bakelite sheets of different
grades using profilometer and AFM have been used to model the asperities in a
Bakelite-RPC. The field configuration in the active volume of the device has
been computed using neBEM-GARFIELD package [http://garfield.web.cern.ch,
http://nebem.web.cern.ch]. The calculation for a typical Bakelite-RPC with a
rectangular ridge of height about 4 micron on one of the Bakelite sheets has shown
a change of around 10% in the field values. A few preliminary results for very simple
models were reported in RPC2010 [S. Biswas et al.]. However, it is obvious that much
more detailed modeling of the device is required in order to investigate the actual
effect of surface irregularities on the detector performance. In this work, several
models with volumes of different shapes and sizes have been used to represent the
measured asperities more realistically. In addition, modelling has been carried out
to simulate the effect of surface treatment with a layer of silicone on the
electrostatic configuration. Trends observed in the computation seem to agree well
with the experimental observations.
Primary authors
Prof.
Nayana Majumdar
(Saha Institute of Nuclear Physics)
Prof.
Supratik Mukhopadhyay
(Saha Institute of Nuclear Physics)
Co-authors
Ms
Purba Bhattacharya
(Saha Institute of Nuclear Physics)
Dr
Saikat Biswas
(GSI Helmholtzzentrum für Schwerionenforschung GmbH)
Prof.
Satyajit Saha
(Saha Institute of Nuclear Physics)
Dr
Subhasis Chattopadhyay
(Variable Energy Cyclotron Centre)
Prof.
Sudeb Bhattacharya
(Saha Institute of Nuclear Physics)
