Post on 19-Dec-2015
Geant4 simulations for the calorimeter prototypes
D. Di Julio, J. Cederkäll, P. Golubev, B. Jakobsson
Lund University, Lund, Sweden
Outline
• Simulation overview– Geometry– Physics list
• Benchmark simulations
• Response to gammas and protons
• Light collection
• Future work
Geometry
• Material: CsI
• Separation distance: 0.4 mm, vacuum
• 15 crystals
10x30
130 mm
15x4
210x10
Physics list
• For gamma:– Low energy package – Photoelectric and
conversion, Rayleigh, Compton Scattering
• For e- and e+ :– Low energy package for e-
– Multiple scattering, ionization, Bremsstrahlung, and annihilation (for e+)
• For protons– QGSP physics list
Preliminary simulations
• Compare with previous calculations• Performed by Thomas Zerguerras• 20 MeV gamma
Large single block:110x110x200mm35x5 array of crystals,
22x22x200mm3
0.1 mm between crystals, space filled with kapton
500 keV gamma
• Large fraction of full energy events in center crystal
• ~60% of events lie in full energy peak in center crystal
• Some energy deposition in surrounding crystals
500 keV gamma
Sum spectrum for entire block, ~91%of the events lie in the full energy peak
On average, 1 crystal out of 15is fired per incident gamma, 6 maxwidth at half max ~ 1 crystal
15 MeV gamma
• Energy deposited in more crystals
• Number of full energy events decreases
• No significant full energy peak in center crystal
15 MeV gamma
Sum spectrum for entire block,full energy peak appears, ~13% of the events lie in the full energypeak
~3 crystals out of 15 fire per incident Gamma,11 at most, width increases ~3 crystals
28 MeV gamma
• Large spread of energy deposition
• Very few fully contained events, no full energy peak in center crystal
28 MeV gamma
Full energy peak can be seen,only about ~2.5% of events lie in full energy peak
4.5 crystals out of 15fire on average, 12 at most, width ~4 crystals
50 MeV protons
• Energy deposited mostly in center crystal, little to no energy spread
180 MeV protons
• Large full energy peak in central crystal
• Some energy deposition in nearby crystals
180 MeV protons
Sum spectrum for entire block,full energy peak appears, ~80% of the events lie in the full energypeak
1.5 crystals out of 15fire on average, 11 at most, width ~1 crystals
Light Collection
• Preliminary simulations to investigate light collection
• Input:– Photon emission spectrum,
light yield, fast and slow time components
– Need absorption length for tracking
– G4LogicalBorderSurface with reflection properties of VM2000 was used for the simulations
D. Motta et al. NIM A 547 (2005) 368.
J.D. Valentine et al. NIM A 325 (1993) 147.
Future Work
• Addition of reflector between crystals
• 2nd prototype geometry
• Light collection in single crystals
• Threshold effects