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X-ray Polarimeter

XPOL schematic diagram

A possible configuration for XPOL. Click the image for larger view

The X-ray Polarimeter (XPOL) is an imaging polarimeter, with polarization sensitivity of 1 percent for a source with a 2–10 keV flux of 1mCrab in a 105 s exposure. XPOL utilizes a fine grid Gas Pixel Detector (GPD) to image the tracks of photoelectrons produced by incident X-rays and determine the direction of the primary photoelectron, which conveys information about the polarization of the incoming radiation. XPOL also has spectrographic capabilities with a resolution of E/ΔE of ~5 at 6 keV and timing information at few ms level. The XPOL´s FOV of 2.5 arcmin × 2.5 arcmin and its spatial resolution is a good match to the mirror point spread function (PSF). See IXO Science Performance Requirements.

Data collected by the XPOL will mainly contribute to high-energy astrophysics, such as the study of Matter under Extreme Condition,Structure and Physics of Jets, and also to test theories of Quantum Gravity.

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Polarimeter Polarimeter

XPOL photograph. Click the image for a larger view

XPOL schematic. Click the image for a larger view

Gas proportional counters are a well-established space technology. Virtually every X-ray observatory from Uhuru (1970) through BeppoSAX (1996) utilized some form of gas counter. Gas Pixel Detectors have been under development for several years. A GPD variant— the Time Projection Chamber polarimeter—is the heart of the GEMS SMEX mission, recently selected by NASA for a 2014 launch.

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Selected References

  • Bellazzini et al., "A polarimeter for IXO", Proceeding of Roma Conference "The Coming of age of X-ray polarimetry", INAF/IASF-Rome, Italy, 2010. Download PDF.
  • A.M.Bykov, Yu.A.Uvarov, J.B.G.M.Bloemen, J.W. den Herder, J.S.Kaastra, "A Model of Polarized X-ray Emission from Twinkling Synchrotron Supernova Shells", MNRAS (in press), 2009. Download PDF.
  • Enrico Costa et al., "XPOL: a photoelectric polarimeter onboard XEUS", Proceedings of SPIE Astronomical Instrumentation 2008 Conference, 23–28 June 2008 Marseille, France, Vol. 7011–15. Download PDF.
  • Muleri, F. et al., Nuclear Instruments and Methods in Physics Research, A 584, 149–159, 2008. Download PDF.

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