Characterization of a crystal for x-ray spectropolarimetric plasma diagnostics

Summary form only given. A well-known feature in many otherwise thermal plasmas is an energetic electron component, whose origin and properties remain to be fully understood. When the energetic electrons have a preferred direction, the X-rays created by the beam can be polarized. In turn, information about the anisotropic electron energy distribution can be obtained from the X-ray spectrum's polarization, and a polarization-containing plasma radiation model. A promising way to perform the appropriate spectropolarimetry uses a crystal that contains two equivalent sets of planes under 120 degrees with each other. These diffract, for a given wavelength, an incident X-ray beam in two directions perpendicular to this beam and to each other.The diffracted X-rays are then linearly polarized perpendicular to each other. The polarization-splitting properties of a quartz crystal cut along the (10-10) plane and diffracting from two (11-20) planes were confirmed with synchrotron radiation from the Advanced Photon Source at the Argonne National Laboratory. The crystal characteristics and requirements for its use to diagnose electron beams in zpinch plasmas will be presented.