15 October 1997 Measurement of x-ray polarization with small-pixel charge-coupled devices
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Abstract
Measuring the polarization of x-rays emitted from cosmological objects yields explanations of the structure which characterize these sources. Polarization detection efficiencies of up to 18% have been measured for two, small pixel, charge coupled devices (CCDs) using an 80% polarized monochromatic synchrotron beam between energies of 7.5 keV and 35 keV. The device efficiencies at less than 15 keV are of particular interest for astronomical purposes where imaging, spectroscopy and polarization measurements can be carried out simultaneously. Polarization measurements using a CCD rely on the preferential direction of the ejected photoelectron along the E-field of the incident x-ray beam. The resultant charge cloud is sampled by the pixellated array of the CCD. It will be shown that the CCD polarization detection efficiency (modulation factor) is a function of the pixel size and the energy of the incident photons. The effect of depletion depth and impact of a field-free layer in the detector are reviewed. The two devices used were a commercial optical CCD, Kodak KAF1400, with 6.8 by 6.8 micrometer squared pixels and a specialized CCD, designed by EEV Ltd., deeply depleted with 4 by 9 micrometer squared pixels.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Joanne E. Hill, Andrew D. Holland, Christian M. Castelli, Alexander T. Short, Martin J. L. Turner, D. Burt, "Measurement of x-ray polarization with small-pixel charge-coupled devices", Proc. SPIE 3114, EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy VIII, (15 October 1997); doi: 10.1117/12.283771; https://doi.org/10.1117/12.283771
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