Space Applications of GeSpace Applications of Geant4 ant4 Polarized ProcessesPolarized Processes
F.Longo+
G.Depaola*
+ University of Ferrara and INFN (Italia)
* National University of Córdoba (Argentina)
OutlineOutline
Astrophysics with Polarized PhotonsDetectors in the Compton regimeSimulation RequirementsGeant4 processesARGO: Compton or Pair telescope?
Polarized Gamma AstrophyicsPolarized 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 RegimeDetectors in the Compton Regime
Principles of operation Polarization measurements
in the Compton regime
Polarization DetectionPolarization Detection
•Modulation Factor (azimuthal distribution of scattered photons )
• Figure of merit of Polarimeter
• Minimum Detectable Polarization
See McConnell (ACT Workshop 2001)
COMPTELCOMPTEL
• Simulation in Geant3 - without the Spacecraft - EM only
• Background simulation• Poor geometry small modulation factor
See McConnell - Kippen (ACT Workshop 2001)
INTEGRALINTEGRAL
Photo ESA
See McConnell (ACT Workshop 2001)
GeometryGeometry
See McConnell (ACT Workshop 2001)
MEGAMEGA
Advanced Compton TelescopeAdvanced Compton Telescope
0.8 m
1 m
1 m
Advanced Compton TelescopeAdvanced Compton Telescope
See McConnell (ACT Workshop 2001)
X-ray polarimetryX-ray polarimetrywith MicroPattern Gas Detectorswith MicroPattern Gas Detectors
Costa et al. 2001
Simulation EffortSimulation Effort
•Improved EM Physics•Kinematic reconstruction of multiple Compton events•Electron and pair tracking•Background simulation efforts•Image deconvolution
See Kippen (ACT Workshop 2001)
RequirementsRequirements
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?Geant4: the answer?
Unified framework (science, background, instrumental effects)
Source & Background modellingDetector descriptionSpace modulesAnalysis tools
ARGO ARGO (Argentine Gamma Observatory)(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
