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X-Ray Polarimetry Workshop SLAC, Stanford, California 9-11 February 2004 |
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Polarization response and calibration of the MEGA medium energy gamma-ray telescope
Gottfried
Kanbach
Max-Planck-Inst. f. Extraterrestrische Physik
gok@mpe.mpg.de
A. Zoglauer, G. Kanbach, R. Andritschke (MPE, Garching, Germany) P. F. Bloser (GSFC, Greenbelt, MD) V. Litvinenko (BNL, Brookhaven, NY)
The Medium Energy Gamma-ray Astronomy telescope MEGA, which detects gamma-rays via Compton scattering and pair creation, has been calibrated at the High Intensity Gamma Source of the Free Electron Laser facility at Duke University during April/May 2003. Exposures to monoenergetic (range 710 keV to 50 MeV, dE/E < 2%), 100% polarized pencil beams allow us to derive the imaging and spectral properties, sensitivity, and field of view of this prototype instrument. Since the gamma-ray test beam is generated by inverse Compton scattering inside a free electron laser, the degree and angle of polarization are completely determined. We describe the measured response of MEGA to these polarized photons in the range below about 5 MeV, where Compton scattering is the dominant detection process. We compare these calibrations to Geant4 simulations, which include polarization effects in the Compton cross section, and use them to estimate the polarization sensitivity of a satellite version of MEGA to a typical high-energy gamma-ray burst.
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For more information, contact
Jennifer Formichelli |
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