1. 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

2. Contents - Introduction - Actuality - Solution method - Results JASS, 2006

3. Introduction JASS, 2006 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

4. Actuality Examples: - ALICE - ATLAS - LHCb - Future CBM The actuality is in a possible upgrade of detectors of relativistic charged particles. JASS, 2006

5. GEANT4 toolkit 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++ Official GEAN4 web site, http://geant4.cern.ch http://geant4.cern.ch JASS, 2006

6. How it works Step 1 of 4. The Volume Space Physical Volume. The matter. JASS, 2006 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.

7. How it works Step 2 of 4. Gamma source and detection plane JASS, 2006 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) Gamma source Physical Volume. The matter. 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

8. How it works Step 3 of 4. Physics JASS, 2006 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 Gamma source Physical Volume. The matter. Detection plane

9. How it works Step 4 of 4. Experiment start-up GEANT4 graphical output window ● GEANT4 show experiment parameters on the screen; we can see particles tracks online JASS, 2006

10. How it works What we are looking for? All processes Current pulse form on detection plane. 1.5 MeV gamma source. Water. Compton Scattering Ionization Effect JASS, 2006

11. Computer cluster From 30 minutes to several hours needed to perform calculations for one run consisting of 10 7 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) Linear speedup JASS, 2006

12. Results (Water) Passage of gamma quanta through 2 mm water layer 4000 The role of different processes in current pulse formation in water JASS, 2006

13. 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

14. Results Photo electric effect Compton ScatteringPairing effect Air Theory GEANT4 20 keV 120 keV Water 55 keV 87 keV JASS, 2006

15. 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

16. Appendix JASS, 2006

17. Acknowledgement S. A. Nemnugin F. F. Valiev S. U. Slavyanov JASS, 2006

18. Thank you for attention JASS, 2006