Institute for Nuclear Research and Nuclear Energy Bulgarian Academy of Science

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

2. 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. H.J. Wollersheim et al., Nuclear Instruments and Methods in Physics Research A 537 (2005) 637–657 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 Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010

3. GEANT4 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. Following the GEANT4 design philosophy the following new physics classes representing the respective processes has been developed: G4ionRadativeElectronCaptureK G4ionRadativeElectronCaptureL G4ionPrimaryBremsstrahlung SecondaryBremsstrahlung Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010

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

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

6. Experimental setup - RISING project FRS – FRagment Separator Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010

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

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

9. 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. 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. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010

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

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

12. 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 6crystal segments 3 detectors per cluster 60 clusters ======================= 6480 individual measuring channels Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010

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

14. 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. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010

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

16. 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. Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010