exl/crystal simulations 2006-02-03 [email protected] b. genolini simulation of nustar crystals...

EXL/crystal simulations

2006-02-03 [email protected] B. Genolini

Simulation of NUSTAR crystals with Litrani

• Presentation of Litrani: simulation of optical photons

• Preliminary results– Light yield– Interface with GEANT4 simulations

Meeting at IPNO, Orsay, France



What is Litrani ?

• General purpose Monte-Carlo program to simulate the propagation of optical photons

• ROOT library (Version: 3.3, with ROOT 4.04/02; Windows, Linux with gcc 3.2)

• Developped at CEA, Saclay, France for GLAST and the CMS calorimeter (http://gentit.home.cern.ch/gentit/litrani)

• Classes and data library from measured materials :– Scintillators: PbWO4, CsI(Tl)– Revetments: Tyvek, VM2000– Detectors: PMT (XP2020), APD– Surface state: depolished, thin slice of air

• Easy to extend the library

LITRANI stands for LIght TRansmission in ANIsotropic media.



Material definition (1)

• All properties parametrized as a function of the wavelength

• Crystal geometry and parameters:– Light emission– Absorption length– Index of refraction

• Revetment:– Diffusion and reflection– absorption

• Glue– absorption length– reflectivity

• PMT definition– Glass window refraction, absorption

length and reflectivity– Photocathode surface and reflectivity– Quantum efficiency



Material definition (2)

• Time profile• Wavelength profile



• Crystal: CsI(Tl) (Saint Gobain), wrapped with reflector (VM2000, Tyveck?)• Geometry:

– [A]: 22 (h) × 22(w) × 200(l) mm– [B]: 22 (h) × 44(w) × 200(l) mm– [C]: 22 (h) × 66(w) × 200(l) mm

• Particles: (500 keV – 30 MeV)• Tests: with (511 and) 662 keV• Readout (on face w × h):

– PMT (Photonis 19 mm Ø, 17 mm PK Ø)– APD (square, 10 mm)

• Goals:– Optimize the readout– Particle localization

• Questions– Energy resolution– Homogeneity– Time response

Requirements for the simulation

w

hl

CsI(Tl)

Readout(PMT, APD)

z

y

x



PIN – CsI(Tl)#2

z

y

x

• Yield over a quarter of the volume (for 50 000 photons emitted), sum over 5 µs• Relative RMS of the yield distribution = contribution of the collection to the resolution /

dispersion dominated by the statistics• Optimistic hypotheses on the PIN, dependence on the crystal doping

Simulation results: yield vs position



Simulation analysis with CsI(Tl) #1

• Wavelength: statistics over the whole simulated volume• Result dependent on the wavelength distribution width chosen for the simulation• Histograms can also be available for a voxel

PMT PIN



Simulated tracks in a single crystal

• Input = ROOT file from GEANT4 simulations by T. Zerguerras• Current algorithm:

– Generate a random yield values from the distribution calculated on the volume– Calculate the number of photons received from those yields and the deposited energy

• Simulation with the PMT and PIN diode (with CsI(Tl) #1)



Conclusion

• The RDD group can carry out a full simulation of the crystal response: resolution and time response

• Next steps– Comparison of simulations with measurements

(source + different crystals: 22, 44, 66 mm)– Refine the models:

• APD response• Scintillator response• Consequences of ageing• Detector noise

exl/crystal simulations 2006-02-03 [email protected] b. genolini simulation of nustar crystals...

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