Transcript St. Petersburg State University. Faculty of Physics

St. Petersburg State University.
Department of Physics.
Division of Computational Physics.
COMPUTER SIMULATION OF
CURRENT PRODUCED BY PULSE
OF HARD RADIATION
Vadim V. Galitsyn
JASS, 2006
Contents
- Introduction
- Actuality
- Solution method
- Results
JASS, 2006
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
JASS, 2006
Actuality
The actuality is in a
possible upgrade of
detectors of relativistic
charged particles.
Examples:
-
ALICE
ATLAS
LHCb
Future CBM
JASS, 2006
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++
JASS, 2006
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.
JASS, 2006
How it works
Step 2 of 4. Gamma source and detection plane
Physical
Volume.
The matter.
Setting up:
●
●
Gamma
source
Detection
plane
●
●
* We were interested by time distribution of secondary electrons at the detection plane and
role of the different physical processes for current pulse formation
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)
JASS, 2006
How it works
Step 3 of 4. Physics
Physical
Volume.
The matter.
Gamma
source
Detection
plane
Before we run the
simulation we must to
determine which
physical processes we
want to see and what
particles are we
working with
Processes:
Photo effect, Compton
scattering, Pairing
effect
Particles:
Gamma, Electron,
Positron
JASS, 2006
How it works
Step 4 of 4. Experiment start-up
●
GEANT4 show experiment
parameters on the screen;
we can see particles tracks
online
JASS, 2006
GEANT4 graphical output window
How it works
What we are looking for?
Current pulse form on detection
plane. 1.5 MeV gamma source.
Water.
Compton
Scattering
All processes
JASS, 2006
Ionization
Effect
Computer cluster
Linear
speedup
From 30 minutes to
several hours needed to
perform calculations for
one run consisting of 107
events
We are using high
performance
clusters for
simulations
In our case (full data
parallelism) speedup
depends linearly on
computing nodes
(theoretical limit of the
Amhdal’s law)
JASS, 2006
Results (Water)
The role of different processes in current
pulse formation in water
Passage of gamma
quanta through
2 mm water layer
4000
JASS, 2006
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
JASS, 2006
Results
Air
Water
20 keV
55 keV
Theory
GEANT4
120 keV
Photo electric effect
87 keV
Compton Scattering
Pairing effect
JASS, 2006
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
JASS, 2006
Appendix
JASS, 2006
Acknowledgement
S. A. Nemnugin
F. F. Valiev
S. U. Slavyanov
JASS, 2006
Thank you for
attention
JASS, 2006