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Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
Institute for Nuclear Research and Nuclear EnergyBulgarian 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
What is the problem?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
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Experimental Spectra
H.J. Wollersheim et al., Nuclear Instruments and Methods in Physics Research A 537 (2005) 637–657
Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
GEANT4GEANT4
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.
Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
GEANT4 Bremsstrahlung physics model representationGEANT4 Bremsstrahlung physics model representation
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Ion, E [MeV]
REC_KREC_KREC_LREC_L
PBPBSEBSEB
Mean free path, λ
Z
Ion, E – ΔE [MeV]
ΔE = f(E, λ)
(Energy losses are calculated by the ATIMA program)
γ, Eγ, (Doppler shifted)
Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
RISING projectRISING 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
Experimental setup - RISING projectExperimental setup - RISING project
FRS – FRagment Separator
Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
Experimental setup -Experimental setup - RISING projectRISING project
“Fast” Beam Campaign
GEANT4 model
RISING + HECTOR detector system
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:52Fe (2+ → 0+) 832 keV
The spectra is Doppler corrected for βt = v/c = 0.45
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.
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Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
RISING projectRISING project
“Stopped” Beam Campaign
GEANT4 model
Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
Simulation results “Stopped” Beam - RISINGSimulation results “Stopped” Beam - RISING
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Spectra for 202Pt
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535 keV
719 keV
(7-)
( 4+)
( 2+)
(0+)
280 μs
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
AGATA projectAGATA 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 long80 mm diameter
6 x 6 crystal segments3 detectors per cluster60 clusters=======================6480 individual measuring channels
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
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.
Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
Simulation results “Stopped” Beam - AGATASimulation results “Stopped” Beam - AGATA
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Agata for 202Pt
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Rising vs Agata
AGATA benefits RISING with its better efficiency.
Workshop on Physics on Nuclei at Extremes, Tokyo Institute of Technology, 26.01.2010
ConclusionConclusion
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.
