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This presentation is based on our August 2003 SPIE conference paper (ps, pdf). Several improvements to the analysis described in that work are currently in progress, such as using Sherpa fits to pulse-height spectra instead of region-of-interest analysis, using different pileup coefficients for BI and FI chips, including 3-photon terms to the pileup corrections, and applying known corrections to the BI QEs.
Results can be extended to longer wavelengths by analyzing LETG/HRC-S data. Order separation is more difficult because of the HRC-S's lack of effective energy resolution, but strong emission lines can provide reliable measurements of 2nd and 3rd order efficiencies. Continuum spectra may also be useful in certain circumstances. One example is the spectrum of V4743 Sgr, in which 1st-order emission is concentrated in a narrow range of wavelengths, so that there is relatively little overlap with 2nd and 3rd orders. Jeremy Drake has provided preliminary results from analysis of V4743 (without QE uniformity corrections) which agree well with LETG/ACIS-S measurments.
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