St. Petersburg State University. Department of Physics. Division of Computational Physics.

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St. Petersburg State University.Department of
Physics.Division of Computational Physics.

• COMPUTER SIMULATION OF CURRENT PRODUCED BY PULSE
  OF HARD RADIATION
• Vadim V. Galitsyn

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Contents

• - Introduction- Actuality- Solution method-
  Results

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Introduction

• The aim of this work is to determine the role of
  a different physical processes for the formation
  of a current pulse produced by a hard radiation
  with a initial gamma energy between 20 keV and 4
  MeV. It is necessary for better understanding of
  detector registration efficiency.
• Relativistic electrons
• Speed of light of the current propagation in the
  detector
• Secondary physical processes effect

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Actuality
The actuality is in a possible upgrade of
detectors of relativistic charged particles.

• Examples
• - ALICE- ATLAS- LHCb- Future CBM

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GEANT4 toolkit
Official GEAN4 web site, http//geant4.cern.ch

• We consider to simulate interaction of particles
  and passage through matter with a GEANT4 Software
  package
• GEANT4 is an open source toolkit for the
  simulation of the passage of particles through a
  matter written on C

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How it works

• Step 1 of 4. The Volume Space

Physical Volume.The matter.
We used Air and Water matter to simulate gamma
passage through. There are many different volume
forms possible to create with the
GEANT4. Cubical geometry of a detector was
considered.
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How it works

• Step 2 of 4. Gamma source and detection plane

• Setting up
• Gamma beam direction
• Number of gamma
• Gamma energy (between 20 keV and 4 MeV energy
  range)
• Fixing detection virtual plane position
  (perpendicular to gamma direction)

Physical Volume.The matter.
Gamma source
Detection plane
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We were interested by time distribution of
secondary electrons at the detection plane and
role of the different physical processes for
current pulse formation
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How it works

• Step 3 of 4. Physics

Before we run the simulation we must to determine
which physical processes we want to see and what
particles are we working with ProcessesPhoto
effect, Compton scattering, Pairing
effect Particles Gamma, Electron, Positron
Physical Volume.The matter.
Gamma source
Detection plane
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How it works

• Step 4 of 4. Experiment start-up

• GEANT4 show experiment parameters on the screen
  we can see particles tracks online

GEANT4 graphical output window
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How it works

• What we are looking for?

Current pulse form on detection plane. 1.5 MeV
gamma source. Water.
Compton Scattering
All processes
Ionization Effect
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Computer cluster
Linearspeedup
In our case (full data parallelism) speedup
depends linearly on computing nodes (theoretical
limit of the Amhdals law)
We are using high performance clusters for
simulations

• From 30 minutes to several hours needed to
  perform calculations for one run consisting of
  107 events

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Results (Water)
The role of different processes in current pulse
formation in water
Passage of gamma quanta through2 mm water layer
4000
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Results (Air)
The role of a different processes in current
pulse formation in the air
Passage of gamma quanta through 1 m air layer at
atmosphere pressure
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Results
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Conclusions

• The role of different physical processes for the
  formation of current pulse was defined
• The differences between a theory and experiment
  was detected
• The forms of a current produced by a pulse of
  hard radiation were defined

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Appendix
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Acknowledgement
S. A. Nemnugin F. F. Valiev S. U. Slavyanov
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Thank you for attention
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