Fabrication and testing of off-plane gratings for future x-ray spectroscopy missions

Soft X-ray spectroscopy is a useful observational tool, offering information about high-temperature (106 - 107 K) astrophysical plasmas and providing useful characterizations of a number of energetic systems, including accreting young stars, cosmic filaments between galaxies, and supermassive black holes. In order to yield high resolution spectra with good signal-to-noise, however, soft X-ray spectrometers must realize improvements in resolving power and effective area through the development of high performance gratings. Off-plane reflection gratings offer the capability to work at high dispersions with excellent throughput, and are a viable candidate technology for future X-ray spectroscopy missions. The off-plane geometry requires a customizable grating meeting distinct fabrication requirements, and a process for producing gratings meeting these requirements has been developed. These fabricated gratings have been evaluated for performance in terms of resolution and diffraction efficiency. Furthermore, these gratings have been conceptually implemented in a soft X-ray spectrometer, the Off-Plane Grating Rocket Experiment (OGRE), whose optical design provides a template for future missions to achieve high performance within a small payload envelope.