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Solar Physics

, Volume 210, Issue 1–2, pp 125–142 | Cite as

RHESSI as a Hard X-Ray Polarimeter

  • Mark L. McConnell
  • James M. Ryan
  • David M. Smith
  • Robert P. Lin
  • A. Gordon Emslie
Article

Abstract

Although designed primarily as a hard X-ray imager and spectrometer, the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) is also capable of measuring the polarization of hard X-rays (20–100 keV) from solar flares. This capability arises from the inclusion of a small unobstructed Be scattering element that is strategically located within the cryostat that houses the array of nine germanium detectors. The Ge detectors are segmented, with both a front and rear active volume. Low-energy photons (below about 100 keV) can reach a rear segment of a Ge detector only indirectly, by scattering. Low-energy photons from the Sun have a direct path to the Be and have a high probability of Compton scattering into a rear segment of a Ge detector. The azimuthal distribution of these scattered photons carries with it a signature of the linear polarization of the incident flux. Sensitivity estimates, based on Monte Carlo simulations and in-flight background measurements, indicate that a 20–100 keV polarization sensitivity of less than a few percent can be achieved for X-class flares.

Keywords

Solar Phys Modulation Pattern Scattered Photon Polarization Signature Polarization Sensitivity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Kluwer Academic Publishers 2002

Authors and Affiliations

  • Mark L. McConnell
    • 1
  • James M. Ryan
    • 1
  • David M. Smith
    • 2
  • Robert P. Lin
    • 3
  • A. Gordon Emslie
    • 4
  1. 1.Space Science CenterUniversity of New HampshireDurhamU.S.A
  2. 2.Space Sciences LaboratoryUniversity of CaliforniaBerkeleyU.S.A
  3. 3.Physics Department and Space Sciences LaboratoryUniversity of CaliforniaBerkeleyU.S.A
  4. 4.Physics DepartmentUniversity of AlabamaHuntsvileU.S.A

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