1. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Institute for Nuclear Research and Nuclear Energy Bulgarian Academy of Science RISING & AGATA detectors in experiments with relativistic beams at GSI : Simulations and comparison with the experiments Pavel Detistov

2. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 What is the problem? Long high energy background tail in the experimental spectra. The passage of heavy ions through the matter is related to the interactions with the electrons from the electronic shells of the matter’s atoms. The main processes identified to be responsible for the high energy gamma-ray emissions in such conditions are:  Radiative Electron Capture process  Primary Bremsstrahlung process  SEcondary Bremsstrahlung process H.J. Wollersheim et al., Nuclear Instruments and Methods in Physics Research A 537 (2005) 637–657

3. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 GEANT4 Following the GEANT4 design philosophy the following new physics classes representing the respective processes has been developed: G4ionRadativeElectronCaptureK G4ionRadativeElectronCaptureL G4ionPrimaryBremsstrahlung SecondaryBremsstrahlung How to create a model to see these processes in action? GEANT4 (GEometry ANd Tracking) tool is a set of libraries written in C++ forming the complete toolkit for simulation of the passage of particles through matter. It contains number of independent categories that could be combined together in a complete simulation model: Geometry, Physical Processes, Event generator, Hits GEANT4 allows development of user defined physical processes that could be used solely or in combination with the standard GEANT4 physics library.

4. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 GEANT4 Bremsstrahlung physics model representation Z Ion, E [MeV] REC_KREC_LPBSEB Mean free path, λ Z Ion, E – ΔE [MeV] ΔE = f(E, λ) (Energy losses are calculated by the ATIMA program) , E γ, (Doppler shifted)

5. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 RISING project 15 Ex-EUROBALL Cluster Detectors HPGe crystal: 78 mm diameter 70 mm length 7 detectors in one cryostat

6. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Experimental setup - RISING project FRS – FR agment S eparator

7. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Experimental setup -RISING project Experimental setup - RISING project “Fast” Beam Campaign GEANT4 model RISING + HECTOR detector system

8. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Simulation results Simulation results “Fast” Beam - RISING Why there is a difference between the simulations and the experiment? RISING Experimental spectra Simulation The physical case: 52 Fe (2+ → 0+) 832 keV The spectra is Doppler corrected for β t = v/c = 0.45

9. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 The background radiation produced by an α particle. Probably, the experimental spectra is an superposition of the spectra seen by the detector from the projectile of interest and the light particle induced spectra, both Doppler corrected for the energy of the projectile. Simulation results Simulation results “Fast” Beam - RISING During the secondary beam transportation and identification a lot of light particles are created and they are flying with the beam.

10. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 RISING project “Stopped” Beam Campaign GEANT4 model

11. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Simulation results “Stopped” Beam - RISING 535 keV 719 keV (7 - ) ( 4 + ) ( 2 + ) (0 + ) 280 μs The physical case: 202 Pt 280 μs (7 - → 4 + ) 535 keV (4 + → 2 + ) 719 keV (2 + → 0 + ) 535 keV

12. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 AGATA project Advanced GAmma ray Tracking Array European project for construction of 4π highly segmented HPGe array that uses the γ - ray tracking concept. HPGe crystal: 90 mm long 80 mm diameter 6 x 6 crystal segments 3 detectors per cluster 60 clusters ======================= 6480 individual measuring channels

13. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Simulation results Simulation results “Fast” Beam - AGATA Simulation RISING Experimental spectra

14. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Simulation results Simulation results “Fast” Beam - AGATA Performance of the AGATA detector array in such experiments will depend strongly on the possibility of the tracking algorithms to track events with higher multiplicity.

15. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Simulation results “Stopped” Beam - AGATA AGATA benefits RISING with its better efficiency.

16. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 Conclusion A model for background simulation has been developed and tested. The simulations have been compared to the experimental results taken from the RISING experimental campaigns. Good agreement between the simulations and experiment is found. The model could be used to estimate background radiation in any realistic experiment involving ions with relativistic energies. Performance of the AGATA detector in similar to RISING experimental conditions is under evaluation. The high multiplicity of the background emission limits usage of the gamma-ray tracking in such conditions. The benefit of AGATA for the “stopped” beam setup is the better efficiency compared to the RISING array.

17. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010 RISING project gRISING Setup