OGREs can see: synchrotron-based diffraction efficiency testing of OGRE diffraction gratings

The Off-plane G rating R ocket E xperiment (OGRE) i s a s ounding r ocket m ission d esigned t o c apture high-resolution spectra of Capella in the soft X-ray range (200-2000eV). Capella is one of the brightest X-ray sources in the sky, and thus ideal for studying the effectiveness o f t hree k ey i nnovative t echnologies: polished-silicon mirror segments, X-ray reflection g ratings, a nd a n i maging s ystem f eaturing f our Electron-Multiplying-CCDs. A prototype grating master was fabricated with thermally activated selective topography equilibration and characterized for OGRE applications. We present the methodology and results of diffraction g rating efficiency measurements for the prototype master grating, conducted at the Advanced Light Source facility at Lawrence Berkeley National Laboratory. The OGRE prototype measured in this work averages ≈40% absolute diffraction efficiency ov er th e me asured bandpass.