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Optical Engineering

Transmission grating spectroscopy and the Advanced X-Ray Astrophysics Facility
Author(s): Mark L. Schattenburg; Claude R. Canizares; Daniel Dewey; Kathryn A. Flanagan; Margaret A. Hamnett; Alan M. Levine; Kenneth S. K. Lum; Ramanujam Manikkalingam; Thomas H. Markert; Henry I. Smith
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Paper Abstract

The use of transmission gratings with grazing-incidence telescopes in celestial x-ray astronomy is reviewed. The basic properties of transmission grating spectrometers and the use of "phased" gratings to enhance the diffraction efficiency are outlined. Special attention is given to the AXAF high-energy transmission grating (HETG) being fabricated at MIT. The HETG operates over the range 0.4 to 8 keV, gives resolving powers of 100 to 1000, effective areas of 10 to 300 cm2, and a minimum detectable line flux of 1 to 10 x 10-6 photons cm-2 s-1. The instrument consists of a single array with two types of membrane-supported grating facets: medium-energy gratings (0.6-μm period, 0.5-μm-thick silver) mounted behind the outer three AXAF mirrors, and high-energy gratings (0.2-μm period, 1.0-μm-thick gold) mounted behind the inner three mirrors. The materials and thicknesses are selected to maximize efficiency throughout the energy band. The facets are fabricated at MIT using a process involving x-ray lithography. AXAF will also carry a low-energy transmission grating (LETG) supplied by the Laboratory for Space Research at Utrecht. It uses mesh-supported grating facets of 1.0-μm period and is optimized for operation down to 80 eV. Gratings are most effective for the study of point sources, but they also give moderate resolution spectra of slightly extended sources and can be used to map the spatial distribution of line-emitting regions.

Paper Details

Date Published: 1 October 1991
PDF: 11 pages
Opt. Eng. 30(10) doi: 10.1117/12.55976
Published in: Optical Engineering Volume 30, Issue 10
Show Author Affiliations
Mark L. Schattenburg, Massachusetts Institute of Technology (United States)
Claude R. Canizares, Massachusetts Institute of Technology (United States)
Daniel Dewey, Massachusetts Institute of Technology (United States)
Kathryn A. Flanagan
Margaret A. Hamnett, Massachusetts Institute of Technology (United States)
Alan M. Levine, Massachusetts Institute of Technology (United States)
Kenneth S. K. Lum, Massachusetts Insitute of Technology (United States)
Ramanujam Manikkalingam, Massachusetts Institute of Technology (United States)
Thomas H. Markert, Massachusetts Institute of Technology (United States)
Henry I. Smith, Massachusetts Institute of Technology (United States)

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