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