Geant4 Polarized Processes - INFN_1_

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					Space Applications of Geant4
Polarized Processes
     F.Longo+
     G.Depaola*


     + University of Ferrara and INFN (Italia)
     * National University of Córdoba (Argentina)
Outline

 Astrophysics with Polarized Photons
 Detectors in the Compton regime
 Simulation Requirements
 Geant4 processes
 ARGO: Compton or Pair telescope?
   Polarized Gamma Astrophyics

      Compton Astrophyics (MeV region)
      Emission Mechanisms (Synchrotron Radiation,
       Bremsstrahlung, Compton Scattering, Photon Splitting)
      Astronomical Sites (Solar Flares , Galactic BH candidates,
       Pulsars, Plerions, AGN, GRB)




See Review by Lei, Dean & Hills (1997)
Detectors in the Compton Regime

 Principles of operation
 Polarization measurements
  in the Compton regime
   Polarization Detection

                                    •Modulation Factor
                                     (azimuthal distribution of
                                      scattered photons )

                                    • Figure of merit of Polarimeter

                                    • Minimum Detectable Polarization




See McConnell (ACT Workshop 2001)
COMPTEL

     • Simulation in Geant3
       - without the Spacecraft
       - EM only
     • Background simulation
     • Poor geometry       small modulation factor




                        See McConnell - Kippen (ACT Workshop 2001)
   INTEGRAL
                                    Photo ESA




See McConnell (ACT Workshop 2001)
   Geometry




See McConnell (ACT Workshop 2001)
MEGA
 Advanced Compton Telescope


           0.8 m




1m
      1m
       Advanced Compton Telescope




See McConnell (ACT Workshop 2001)
    X-ray polarimetry
    with MicroPattern Gas Detectors




Costa et al. 2001
       Simulation Effort
   •Improved EM Physics
   •Kinematic reconstruction of multiple Compton events
   •Electron and pair tracking
   •Background simulation efforts
   •Image deconvolution




See Kippen (ACT Workshop 2001)
Requirements

   Physical Simulation
   EM physics 1keV – 50 MeV
   Better description of Compton (doppler
    broadening and polarization)
   Hadronic cascades, spallation, isotope
    production, radioactive decay
   Time dependency
   Models of background
   Instrumental effects
   Reconstruction efforts
                              See Kippen (ACT Workshop 2001)
Geant4: the answer?

 Unified framework (science,
  background, instrumental effects)
 Source & Background modelling
 Detector description
 Space modules
 Analysis tools
ARGO (Argentine Gamma Observatory)

   Proposal to Argentina National Agency for
    Scientific and Technological Development
   Payload weight (40-60 kg ~ AGILE)
   Power 60 W
   Use of Silicon Detectors
   Measurements of Polarization from
    Gamma Rays
   G4 crucial to evaluate the sensibility from
    Gamma Conversion or Compton
    Scattering

				
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posted:4/3/2013
language:English
pages:16