Maria Catarina Espírito-Santo, Patrícia Gonçalves, Mário Pimenta, Pedro Rodrigues, Bernardo Tomé, Andreia Trindade - PDF

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Maria Catarina Espírito-Santo, Patrícia Gonçalves, Mário Pimenta, Pedro Rodrigues, Bernardo Tomé, Andreia Trindade SpaceGEANT4 Simulation Framework EUSO Analysis and Simulations AMS/RICH Radiator Simulations

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Maria Catarina Espírito-Santo, Patrícia Gonçalves, Mário Pimenta, Pedro Rodrigues, Bernardo Tomé, Andreia Trindade SpaceGEANT4 Simulation Framework EUSO Analysis and Simulations AMS/RICH Radiator Simulations Simulation Framework Overview Simulation requirements Description of different AMS and EUSO related detector geometries: GEANT4 Interface with alternative sets of primary event generators : GEANT4 Integration of readout electronics, signal digitization and event reconstruction: DIGITsim OO-technology for event data persistency and data analysis : ROOT, LCG PI/AIDA, LGC POOL Radiation transport: GEANT4 toolkit Signal digitization: DIGITsim module Baseline Configuration Analysis & Event Storage: ROOT Options Analysis: LCG PI/AIDA Event Storage: LCG POOL Analysis (ROOT & PI/AIDA) GEANT4 DIGITsim Persistency (ROOT & POOL) CVS Code Management EUSO : Extreme Universe Space Observatory EUSO will detect Extensive Air Showers (EAS) light from above! Fluorescence photons isotropically produced at different depths Čerenkov photons collimated with the shower and diffused in a surface ULTRA: a supporting experiment for EUSO (UV Light Transmission and Reflection in the Atmosphere) Study the detection of EAS Čerenkov light reflected on different surfaces (ground,water, ) Two main detectors: Ground array! measures the shower size and axis direction UV telescope! detects the reflected ultraviolet Čerenkov light UV telescope β θ H B D C L A Ground array The ULTRA array stations (Phillips XP3462B) NE102A scintillator: Polystirene based H:C ratio = 10:9 density =1.032 g/cm3 Refractive index = 1.58 (NE102A) Absorption length =160 cm Light yield=10000 Photons/MeV Emission spectrum Optical boundaries: UNIFIED model Scintillator-Air interface: TYPE : dielectric-dielectric FINISH : ground Air-Painted aluminium interface: TYPE: dielectric-dielectric FINISH : GroundFrontPainted Event data storage Events are stored under a ROOT Tree organization EventForTree is the ROOT persistent class For each event, the EventForTree object contains namely: Primary particle initial position and momentum Total energy deposited in the scintillator Number of detected optical photons TClonesArray(s) of StoreScintHit and StoreOpticalPhoton objects StoreScintHit StoreOpticalPhoton StoreScintHit Energy x,y,z... StoreOpticalPhoton Energy x,y,z... Energy x,y,z Energy x,y,z Simulation results Energy deposited in the scintillator Light collection uniformity # outgoing photons Source Position (cm) Digitization in the ULTRA SpaceGEANT4 application 4. Signal shaping and amplification 5. Time sampling, analog to digital conversion 3. Photoelectron production and signal generation PMT AMP ADC DIGITSim 1. Energy deposition in the scintillator, photon generation 2. Light propagation and collection GEANT4Space Implementation DIGITsimULTRAPulse Inherits from DIGITsimVPulse Contains the ULTRA pulse shape definiton DIGITsimULTRAAmplifier V(t) = V max e 1 2ϖ 2 log 2 t t ( 0 ) Inherits from DIGITsimVAmplifier The LIP-PAD ADC/Coder parameters: Frequency 100 MHz, 10 bits, 8 time samples, voltage range 0-1 V Photodetector: Energy deposited in the scintillator (E dep ) directly used to obtain the total collected charge (Q) : Q = E dep Y ε coll ε QE ε acc G Total charge Pulse shape Q Amplifier response simulation ADC/Coder response digitized information An example... Y=10 4 photon/mev ε coll 0.10 ε QE 0.15 ε acc 1.0 G Amplifier gain 50 V/A Pulse shape # 8 ns # ω 1 Pedestal=0 B.Tome ESA R&D Contracts Final Presentation Days The ULTRA UV telescope Aluminum housing Fresnel lens: 457 mm diameter 457 mm focal length 5.6 grooves/mm UV transmitting acrylic Challenge!! Photomultiplier Fresnel lens description in the SpaceGEANT4 framework SpaceGEANT4FresnelLens Class Lens defined through a parameterised replication of G4Cons volumes Lens grooves are frustra of cones 5.6 grooves/mm Simulation of the UV telescope (I) Simulation of the UV telescope (II) Light collection efficiency Light collection efficiency vs position GEANT4 potential explored in detailed studies The AMS spectrometer is constituted by different subdetectors surrounded by a superconducting magnet, which aims at characterising cosmic rays before reaching the earth atmosphere. LIP s collaboration in AMS is centered in the RICH Ring Imaging Cherenkov detector. The light emitted by charged particles with velocity greater than the speed of light in the radiator enables to reconstruct their charge and velocity The number of photons is proportional to Z 2 The Cherenkov cone opening angle is related to the velocity β, by: cos(θ c )=1/(β n). Aerogel Plexiglas Aerogel tiles n=1.03 Clarity= Abs_length=100.cm 11.3 cm x 11.3 cm x 3.0 cm, gap 0.1 cm Variable number NTilesx x NTilesy Plexiglas foil n=1.49 Abs_length~100.cm (λ =400 nm) below the Aerogel tiles ( size depends on NTilesx x NTilesy ) Surface description (for aerogel-air and plexi-air interface) Type - dielectric_dielectric Model Unified Finish Ground 80 GeV electron The relevance of the direction of the transmitted photons... The Cherenkov cone opening angle is related to the velocity β, by: θ c cos(θ c )=1/(β n). = β/β(hit)=tan(θ c ) θ c Test beam data (2002) β rec. -β exp. An empirical model with Geant3: p( α) d α exp 2 sin α d(sin 2 2σ α 2 α) for P P(scattering.) aerogel air Optical photon β rec. -β exp. Fit to data: Aerogel P(scattering) σ α Mats ± ±3 Mats ± ±2 Mats n 0.33± ±3 Nov ± ±1 Nov ± ±4 A more precise description of the photon scattering in aerogel Atomic Force Microscopy (AFM): Study of the surface of different aerogel types : from different manufacturers /with different refractive indices. Contribute for the choice of the aerogel type to be used in the AMS RICH flight configuration? Obtain aerogel surface mappings and/or estimate effective parameters for the surface. Aerogel: n=1.03 (Matsushita ) µm z=150nm/div Aerogel: n=1.05 (Matsushita ) z=100nm/div µm Can the unified model describe photon scattering in aerogel? [ g( α, )] ' T ( θt, n, n ) t, 0 In the unified model the direction of the transmitted photons is only parameterised by a Gaussian distribution of resolution σ α (α is the difference between the average surface normal and the microfacet slope). agl air σ α STANDARD NEW Extension to the unified model ChooseTransmission PssT=prob_ss/(prob_ss+prob_sl) rand=g4uniformrand T C sl /(C ss +C sl ) T C ss /(C ss +C sl ) rand =0 && rand PssT N LobeTransmission Parameterisation of the radiant intensity for transmitted photons: obtained from AFM measurements! Y SpikeTransmission The detailed description of photon scattering in aerogel is fundamental to understand the performance of the AMS RICH detector, both in what concerns the charge and the velocity reconstruction. Given the characteristics of the aerogel surfaces the Unified model, in its present implementation, does not describe accurately the direction of the Cerenkov photons after leaving the radiator. An interface class G4VBoundaryMicrofacetModel was implemented in Geant4 enabling the choice of different surface description frameworks. - AFM preliminary measurements compatible with parameters fitted from data for Geant3. - The implementation of surface mappings as a concrete class is underway. - Extension to the UNIFIED model with realistic transmission is being studied. Analysis (ROOT & PI/AIDA) A complete simulation framework was implemented Simulation tools were developed: GEANT4 DIGITsim Persistency (ROOT & POOL) CVS Code Management EUSO/ULTRA : Fresnel lens description AMS/RICH: realistic (AFM measurements) optical surface description Geant4 Applications for Astroparticle Experiments presented at IEEE/NSS 2003 conference accepted for publication GEANT4SpaceApplication: Class Overview SpaceGEANT4DataManager Interface class to data histograms and analysis (ROOT or PI) SpaceGEANT4POOLManager Interface class to POOL storage system SpaceGEANT4PrimaryGeneratorAction Uses ESA General Particle Source Module SpaceGEANT4PhysicsLists Standard EM physics process for photons, electrons, DIGITsim - Digitization Module Re-use of ClearPEM DIGITsim module (based on CMS/ECAL approach) Set of abstract interfaces for: Detector charge signal simulation A/D conversion Trigger implementation Pulse amplitude and time reconstruction The electronics configuration is stored in a macro file and can be changed interactively Example of input data: QE, bias voltage, gain, current dark noise (dependence on temperature) Amplifier electronic noise DIGITsimElectronics DIGITsimReconstruction Pulse shape and ADC parameters MC Hits MC / Exp Digits Trigger configuration (for example: digital Reconstructed Hits DIGITsim - Digitization Module Online extraction of parameters (time/energy) DIGITsimStoreDigit OpticalHits ChargeHits Time Pulses ADCDataframes Reco Event Front-End (Detector/Electronics) DAQ & Trigger Event Reconstruction Configuration DB Conditions DB Interface to MySQL databases (calibration/threshold stuff) Persistency & Analysis ROOT for data analysis and persistency (baseline solution) A persistent object EventForTree (stored in ROOT Tree organization) has been defined Used to hold physical quantities that characterize detector response and primary particle characteristics Since Jan 2004 Introduction of PI/LCG application (Linux 7.3/g++3.2) Provides AIDA native histograms and ROOT histograms using the same code Histogram analysis can now be performed with different tools (ROOT/JAS3/...)
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