X-ray polarimetry and position measurement using the photoeffect and charge diffusion in a CCD

A new method of X-ray polarimetry based on the photoeffect in a highly segmented silicon charge coupled device (CCD) has been established using monochromatic synchrotron radiation and planar channeling radiation. For the smallest pixel dimensions (6.8 × 6.8 μm2) available today in commercial optical CCD cameras an analyzing power for linear polarization in the order of 10% has been measured at energies above 10 keV. A strong energy dependence is observed in the energy range from 15 to 40 keV. In addition to events due to the photoeffect in the thin depleted front layer of the CCD, also diffusion spread events resulting from far more abundant conversions deeper inside the chip were found to be very useful for simultaneous measurements of polarization, energy and position with sub-pixel, submicron impact accuracy (0.9 μm rms at 15 keV). The spatial accuracy is in accord with expectations from Monte-Carlo simulations.