A high energy phase retarder for the simultaneous production of right- and left-handed circularly polarized x rays

Abstract

We have fabricated and characterized the perfoimance of a monolithic Ge Bragg-Laue phase retarder capable of simultaneously producing both right-and left-handed circularly polarized xrays. The energy range of operation of the phase retarder is between 50 and 100 keV making it well suited to the measurement of spin-dependent Compton profiles within the impulse approximation, primarily because of the increased momentum resolution and larger Compton scattering cross section available at these higher incident energies. Although the phase retarder was optimized for operation at 86 keV, it can produce highly circularly polarized x-rays over a substantial energy range. The perfoimance of the phase retarder was tested via magnetic Compton scattering measurements on an Fe sample at the undulator A of the Advanced Photon Source. It was found to perform well in terms of flux and degree of circular polarization thereby greatly reducing the data collection times required for this inherently weak scattering process.