SXRP

In this paper the authors describe an X-ray polarimeter which will be flown on the SPECTRUM-X-Gamma mission. The instrument exploits three distinct physical processes to measure polarization: Bragg reflection from a graphite crystal, Thomson (Compton) scattering from a metallic lithium target, and photoemission from a Cesium Iodide photocathode. The polarimeter is separated into two instruments. One instrument consists of a graphite Bragg crystal, a lithium Thomson scattering target, and four gas proportional chambers for X-ray detection. The other instrument is made up of a CsI photocathode and the associated electron detector. This instrument makes use of the recently discovered polarization dependence of X-ray photoemission from CsI. The polarimeter will make possible sensitive measurements of several hundred known X-ray sources, an increase of two orders of magnitude over the X-ray polarimeters flow to date. These polarization measurements will allow us to constrain the geometry of gas flow in X-ray binaries, differentiate between current models for X-ray emission in radio pulsars, detect nonthermal components in supernova remnants, determine the radiation mechanisms in active galactic nuclei, and search for inertial frame dragging (Lense-Thirring effect) around the putative black hole in Cygnus X-1