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3 February 2004 Chandra LETG higher-order diffraction efficiencies
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Accurate calibration of the Chandra Low Energy Transmission Grating (LETG) higher-order (|m|>1) diffraction efficiencies is vital for proper analysis of spectra obtained with the LETG's primary detector, the HRC-S, which lacks the energy resolution to distinguish different orders. Pre-flight ground calibration of the LETG was necessarily limited to sampling a relatively small subset of spectral orders and wavelengths, and virtually no higher-order data are available in the critical region between 6 and 10 Å. In this paper, we describe an analysis of diffraction efficiencies based on in-flight data obtained using the LETG's secondary detector, the ACIS-S. Using ACIS, the relative efficiency of each order can be studied out to |mλ| ~ 80 Å, which is nearly one-half of the LETG/HRC-S wavelength coverage. We find that the current models match our results well but can be improved, particularly for the even orders just longward of the Au-M edge at 6 Å.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Bradford J. Wargelin, Peter W. Ratzlaff, Deron O. Pease, Vinay L. Kashyap, and Jeremy J. Drake "Chandra LETG higher-order diffraction efficiencies", Proc. SPIE 5165, X-Ray and Gamma-Ray Instrumentation for Astronomy XIII, (3 February 2004);


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