3 February 2004 Characterizing nonlinearities in the Chandra LETGS + HRC-S dispersion relation
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Abstract
The dispersion relation for the Chandra Low Energy Transmission Grating Spectrometer (LETGS) is known to better than 1 part in 1000 over the wavelength range 5-150 Å. A recent resolution of a data processing software bug that lead to a systematic error in the computation of photon wavelengths has allowed us to trace further discrepancies in the dispersion relation to the boundaries between different microchannel plate segments of the HRC-S imaging detector. However, data acquired during in-flight calibration with the HRC-S detector have always shown the presence of additional non-linear deviations in the positions of some spectral lines by as much as 0.05 Å, which is of the order of a full width half maximum (FWHM) of a line profile. These latter effects are thought to be caused by spatial non-linearities in the imaging characteristics of the HRC-S detector. Here, we present an improved dispersion relation for the LETG+HRC-S and new methods to help characterize the spatial non-linearities. We also describe an empirical approach that might be used to help improve the position determination of photon events.
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Sun Mi Chung, Sun Mi Chung, Jeremy J. Drake, Jeremy J. Drake, Vinay L. Kashyap, Vinay L. Kashyap, Peter W. Ratzlaff, Peter W. Ratzlaff, Bradford J. Wargelin, Bradford J. Wargelin, } "Characterizing nonlinearities in the Chandra LETGS + HRC-S dispersion relation", Proc. SPIE 5165, X-Ray and Gamma-Ray Instrumentation for Astronomy XIII, (3 February 2004); doi: 10.1117/12.509360; https://doi.org/10.1117/12.509360
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