Progress in the development of critical-angle transmission gratings

Recently developed Critical-Angle Transmission (CAT) grating technology in combination with x-ray CCD cameras and large collecting-area focusing optics will enable a new generation of soft x-ray spectrometers with unprecedented resolving power and effective area and with at least an order of magnitude improvement in figures-of-merit for emission and absorption line detection. This technology will be essential to address a number of high-priority questions identified in the Astro2010 Decadal Survey “New Worlds New Horizons” and open the door to a new discovery space. CAT gratings combine the advantages of soft x-ray transmission gratings (low mass, relaxed figure and alignment tolerances, transparent at high energies) and blazed reflection gratings (high broad band diffraction efficiency, utilization of higher diffraction orders to increase resolving power). We report on progress in the fabrication of large-area (31× 31 mm) free-standing gratings with two levels of low-blockage support structures using highly anisotropic deep reactive-ion etching.