EXL/crystal simulations 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

EXL/crystal simulations B. Genolini 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 ( 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.

EXL/crystal simulations B. Genolini 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

EXL/crystal simulations B. Genolini Material definition (2) Time profile Wavelength profile

EXL/crystal simulations B. Genolini 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 h l CsI(Tl) Readout (PMT, APD) z y x 

EXL/crystal simulations B. Genolini PIN – CsI(Tl)#2 z y x Yield over a quarter of the volume (for 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

EXL/crystal simulations B. Genolini 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

EXL/crystal simulations B. Genolini 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)

EXL/crystal simulations B. Genolini 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