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