CBM radiation studies within CbmRoot

1
CBM radiation studies within CbmRoot

• Motivations
• Radiation effects
• First results
• Conclusion

2
Motivations

• Radiation background prediction at high intensity
  Heavy Ions collider rely heavily on Monte Carlo
  transport programs
• Obtaining experimental data for all the component
  of the radiation field is difficult -gt
  uncertainties remains
• Need to verify results using differents MC !
• First study Native FLUKA (simplified CBM
  geometry)
• CbmRoot using Virtual Monte Carlo
• Geant3 GCalor
• Geant4
• TFluka

3
Radiation effects

• Ionizing radiation (energy deposited) Trapped
  charges resulting in threshold shifts and leakage
  current
• Units 1 Gray 100 rad
• Non-Ionizing radiation (NIEL) it corresponds to
  atomic displacement in the lattice affecting
  bipolar and optical devices (Displacement damage)
• Units 1 MeV neutrons equivalent / cm2

4
Non Ionizing Energy Loss (1)

• Displacement damage on Si lattice proportional to
  non ionizing energy transfer (NIEL) ( n, p,
  p/-,e).
• Other particles (assumption)
• Muons are considered as electrons (EM weak
  only)
• Others hadrons , mainly Kaons are counted as 1
  n_eq
• To characterize the damage efficiency of a
  particle at E
• Use of the normalized damage function
  D(E)/D(1Mev)
• Tables taken from A.Vasilescu and G. Lindstroem
• ( http//sesam.desy.de/menbers/gunnar/Si-func
  .htm)
• Normalization of hadron fluence F
• F (1 MeV n-eq) ? (D(E)/D(1 MeV)) F(E)
  dE
• with D(1 MeV) 95 MeV mb.

5
Non Ionizing Energy Loss (2)
6
Implementation in CbmROOT

• Radiation study special mode
• CbmRunSimSetRadRegister(kT
  RUE)
• The stepping in CbmMCApplication is intercepted
• Singleton class CbmGridManager
• Fill the user defined Meshes
• Convert to radiation units if needed
• TID convertion to rad
• Fluence convertion to NIEL ( 1 MeV neutron
  equivalent)

7
CbmMesh Class
CBMMesh

• Mesh Geometry independant of
• the Simulation geometry (TGeo)

fillTID() fillFluence() fillSEU()

• The Mesh can be placed anywhere to
• score TID, Fluence or SEU

CBMMesh2D
CBMMesh3D

• 2D or 3D cartesian mesh geometry
• based on 2D or 3D Root Histogram

TH2D
TH3D
8
Scoring mechanism
j

• .

Fluence (cm-2)
?ij S Lk / Vij k
Lk track length of kth track
i
Energy deposition (GeV/cm3)
Eij S Ek / Vij k
Energy deposited of kth track
9
Radiation study settings

• Geometry
• Standard "geo" files are used .
• Setup can be easily changed ..
• CBM cave is implemented
• Primary sources
• UrQmd Generator (Au-Au mbias collisions )
• Secondaries (transport)
• Hadrons, electrons, muons 1 MeV
• electrons bremsstrahlung 0.1 keV
• Delta rays 50 KeV
• Low-energy neutrons Elt 20 MeV (GCALOR)

10
CBM Cave Detectors (CbmRoot)
11
Scoring planes
MVDSTS Scoring planes
MUCH scoring planes
12
First Results MVD at Z 5cm (TID)
FLUKA
GEANT3GCALOR
x(cm)
13
First Results MVD at Z5 cm (Fluence)
FLUKA
GEANT3GCALOR
14
Simulation comparisons (TID)
MVD0 (TID) _at_ Z 5 cm
Fluka shows lower Energy Deposition in Si (150 µm)
15
Simulation comparisons (Fluence)
MVD0 (fluence) _at_ Z 5cm

• Geant3 shows an asymmetry in Xgt0 direction

• Fluka and Geant4 are in good agreement

16
Wiki page Radiation Studies
17
Conclusion

• CbmRoot is used for radiation level
• studies
• Cbm-Wiki Documentation RadiationStudies
• On going work
• Study different geometries
• Study with other Monte Carlo ( Geant4 , TFluka )