Fabrication and performance of blazed transmission gratings.pdfVIP

Fabrication and performance of blazed transmission gratings for x-ray astronomy Ralf K. Heilmann, Minseung Ahn, and Mark L. Schattenburg Space Nanotechnology Laboratory, MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA ABSTRACT We have developed a new type of soft x-ray diffraction grating. This critical-angle transmission (CAT) grat- ing combines the advantages of traditional transmission gratings (low mass, extremely relaxed alignment and flatness tolerances) with those of x-ray reflection gratings (high efficiency due to blazing in the direction of grazing-incidence reflection, increased resolution due to the use of higher diffraction orders). In addition, grating spectrometers based on CAT gratings are well-suited for co-existence with high-energy focal plane microcalorime- ter detectors as planned for the Constellation-X mission, since most high-energy x rays are neither absorbed nor deflected, and arrive at the telescope focus. We describe the CAT grating principle and design, and fabrication and x-ray diffraction efficiency results for a CAT grating with 1742 lines/mm. We have observed up to 46% diffraction efficiency in a single order, and up to 55% at blaze at extreme ultraviolet wavelengths. We present our recent fabrication and soft x-ray diffraction results for 200 nm-period (5000 lines/mm) gratings. Keywords: x-ray optics, Constellation-X, critical-angle transmission grating, x-ray spectroscopy, blazed trans- mission grating, extreme ultraviolet, soft x-ray 1. INTRODUCTION X-ray spectroscopy provides invaluable quantitat