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Update to Absolute QE – Photon Flux. Need to know illumination power at CCD Measure illumination power in integrating sphere during QE measurements Use K (= power at CCD/Power at sphere) to determine light level at CCD What if K is not constant but K( l )?
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Update to Absolute QE – Photon Flux • Need to know illumination power at CCD • Measure illumination power in integrating sphere during QE measurements • Use K (= power at CCD/Power at sphere) to determine light level at CCD • What if K is not constant but K(l)? • Measure K for newly design integrating sphere • Better uniformity at CCD? • No need to 2-sphere illumination Scarpine, CCD Meeting
K Factor from Monochromator • K appears to depend on l • Is this dependence in illumination system or photodiode calibration? • Could have a ~10% effect on QE measurement in near IR Scarpine, CCD Meeting
K from Monochromator and Filter Wheel Scarpine, CCD Meeting
Conclusion • Is K a function of l or this in the photodiode calibration? • Is there some l dependent absorber in system? • Either way, this will change the shape of the absolute QE curve Scarpine, CCD Meeting