A Soft X-ray Polarimeter Designed for Broad-band X-ray Telescopes

TL;DR

This paper introduces a broad-band soft X-ray polarimeter that uses innovative gratings and multilayer optics to measure X-ray polarization with high efficiency across 0.2 to 0.8 keV, suitable for space telescopes.

Contribution

It presents a novel design combining critical angle transmission gratings and multilayer-coated paraboloids for efficient X-ray polarization measurement.

Findings

Achieves over 50% modulation factor across 0.2-0.8 keV band

Uses radial dispersion and ring imaging for polarization analysis

Compatible with Constellation-X telescope optics

Abstract

A novel approach for measuring linear X-ray polarization over a broad-band using conventional imaging optics and cameras is described. A new type of high efficiency grating, called the critical angle transmission grating is used to disperse soft X-rays radially from the telescope axis. A set of multilayer-coated paraboloids re-image the dispersed X-rays to rings in the focal plane. The intensity variation around these rings is measured to determine three Stokes parameters: I, Q, and U. By laterally grading the multilayer optics and matching the dispersion of the gratings, one may take advantage of high multilayer reflectivities and achieve modulation factors over 50% over the entire 0.2 to 0.8 keV band. A sample design is shown that could be used with the Constellation-X optics.