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Volume 358 - 36th International Cosmic Ray Conference (ICRC2019) - CRI - Cosmic Ray Indirect
Non-linearity correction of PMT response on the observed particle densities in GRAPES-3
A. Chandra,* S. Ahmad, M. Chakraborty, S.R. Dugad, S.K. Gupta, B. Hariharan, Y. Hayashi, S.S.R. Inbanathan, P. Jagadeesan, A. Jain, P. Jain, V.B. Jhansi, S. Kawakami, H. Kojima, S. Mahapatra, P.K. Mohanty, S.D. Morris, P.K. Nayak, A. Oshima, D. Pattanaik, P.S. Rakshe, K. Ramesh, B.S. Rao, L.V. Reddy, S. Shibata, F. Warsi, M. Zuberi
*corresponding author
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Pre-published on: 2019 July 22
Published on:
Abstract
The GRAPES-3 (Gamma Ray Astronomy at PeV EnergieS-3) experiment has been
designed to study the composition and energy spectrum of primary cosmic rays
(PCRs) over TeV - PeV range. It is equipped with 400 plastic scintillators
covering an area of 25000 m$^2$ and a muon detector spread in an area of
560 m$^2$. The precise measurement of particle densities from each detector
is very important for any air shower experiment. Photo-multiplier tubes (PMT)
are widely used as a transducer to collect the light produced in detector
medium to electric signals. These signals are then processed to measure the
particle densities. However, these PMTs tend to show non-linearity and
saturation at higher signals due to the large shower core landing near the
detector. The GRAPES-3 detectors record $\sim$ (50 -70) particles in the
linear range. This results in improper shower size estimation near the knee
energy. In order to overcome this situation and to estimate the correct shower
size, a systematic approach has been devised and demonstrated to correct the
particle density beyond the linear range. It is seen from the method allows us
to estimate particle densities $\sim$ (500 - 800) which can improve the
measurements beyond knee.
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