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Proceedings Paper

Hard-x-ray polarimetry with the Ramaty high energy solar spectroscopic imager (RHESSI)
Author(s): Mark L. McConnell; David M. Smith; A. Gordon Emslie; Robert P. Lin; James M. Ryan
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Paper 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 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.

Paper Details

Date Published: 14 February 2003
PDF: 12 pages
Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003); doi: 10.1117/12.458879
Show Author Affiliations
Mark L. McConnell, Space Science Ctr., Univ. of New Hampshire (United States)
David M. Smith, Space Sciences Lab., Univ. of California/Berkeley (United States)
A. Gordon Emslie, The Univ. of Alabama in Huntsville (United States)
Robert P. Lin, Univ. of California/Berkeley (United States)
Space Sciences Lab., Univ. of California/Berkeley (United States)
James M. Ryan, Space Sciences Ctr., Univ. of New Hampshire (United States)

Published in SPIE Proceedings Vol. 4843:
Polarimetry in Astronomy
Silvano Fineschi, Editor(s)

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