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Quantum Efficiency Calibration of AXAF CCDs from 2 - 10 keV

Herbert L. Manning, Stephen E. Jones, Steve E. Kissel,
Marshall W. Bautz, and George R. Ricker
Center for Space Research, Massachusetts Institute of Technology
Cambridge, Massachusetts, 02139


We describe methods used to measure the X-ray detection efficiency of reference CCDs for the AXAF CCD Imaging Spectrometer in the spectral range between 2 keV and 10 keV. The reference CCDs are identical to and are used as calibration transfer standards for the actual flight CCDs. Both radioactive (Fe) and fluorescent X-ray sources are used to illuminate the CCDs, providing a range of discrete emission lines to cover the energy band. A Si(Li) solid state detector is inserted into the beam to provide absolute calibration from 2 - 10 keV (where the Si(Li) detection efficiency can be calculated from first principles). The response function of the Si(Li) detector is discussed, along with factors used to obtain CCD efficiency parameters from the raw data. Calibration geometry and typical data are also presented.

KEYWORDS: ACIS, AXAF, calibration, CCD, Si(Li) detector, detection efficiency