This directory contains quantum efficiency vs energy tables for each ACIS flight detector (one file per detector, with the detector focal plane position indicated by the first two characters of the filename.) Each file contains an ascii header filed by an ascii table. See the file header for details. Header information is reproduced in this file (README_qe_0804.) A listing of the QE data files follows: -rw-r--r-- 1 edgar 1015068 Aug 17 11:30 i0_w203c4r_eff_0700_release.qdp -rw-r--r-- 1 edgar 1015066 Aug 17 11:30 i1_w193c2_eff_0700_release.qdp -rw-r--r-- 1 edgar 1014957 Aug 17 11:30 i2_w158c4r_eff_0700_release.qdp -rw-r--r-- 1 edgar 1015067 Aug 17 11:30 i3_w215c2r_eff_0700_release.qdp -rw-r--r-- 1 edgar 1014961 Aug 17 11:30 s0_w168c4r_eff_0700_release.qdp -rw-r--r-- 1 edgar 1006354 Aug 17 11:30 s1_d36.qdp -rw-r--r-- 1 edgar 1014711 Aug 17 11:30 s2_w182c4r_eff_0700_release.qdp -rw-r--r-- 1 edgar 1006046 Aug 17 11:30 s3_d46.qdp -rw-r--r-- 1 edgar 1014922 Aug 17 11:30 s4_w457c4_eff_0700_release.qdp -rw-r--r-- 1 edgar 1015106 Aug 17 11:30 s5_w201c3r_eff_0700_release.qdp !Release notes for ACIS CCD quantum efficiency curves, 24 July 2000 !C. Grant cgrant@space.mit.edu for the ACIS SI Team. ! !Filenames: ! i0_w203c4r_eff_0700_release.qdp ! i1_w193c2_eff_0700_release.qdp ! i2_w158c4r_eff_0700_release.qdp ! i3_w215c2r_eff_0700_release.qdp ! s0_w168c4r_eff_0700_release.qdp ! s1_w140c4r_eff_0700_release.qdp ! s2_w182c4r_eff_0700_release.qdp ! s3_w134c4r_eff_0700_release.qdp ! s4_w457c4_eff_0700_release.qdp ! s5_w201c3r_eff_0700_release.qdp ! !where ! the first two characters indicate detector position in the focal plane; !and ! wxxxcyy indicates CCD serial number (e.g, w182c4r) ! !Format: !ASCII table suitable for use with qdp. The files contain this !message, followed by a 9-line qdp header which identifies the device. !Following the qdp header there are two columns: !1) Energy (keV) !2) Quantum Efficiency (for ASCA grades 0,2,3,4,6) ! !Description: !This release is an update to the previous release of August 1998. !These QE curves describe at-launch performance and DO NOT account !for any radiation-induced change in quantum efficiency that occurred !after the launch of Chandra. The only change from the previous release !is in the energy range and energy step size. The energy range has been !increased to 0.6 to 12 keV and the energy step size has been decreased !to a fixed grid of 0.2 eV in order to better match the energy resolution !of the spectroscopic gratings particularly over the absorption edges of !Oxygen, Silicon, and Nitrogen. This step size oversamples the original !measurements of ACIS quantum efficiency. ! !Ten files, one for each focal plane detector, are released. !The predictions are for ASCA grades 0,2,3,4,6, with !the following event and split-event thresholds: !Chip Type Event Threshold Split Threshold ! (adu) (electrons, (adu) (electrons, ! approximate) approximate) !FI 38 40 13 14 !BI 20 26 13 15 !(adu = analog-to-digital converter unit converter units) ! !Detectors S1 and S3 are back-illuminated (BI); the other detectors are !front-illuminated (FI). ! !These estimates were derived from MIT CSR subassembly calibration !measurements, !and reflect the spatially averaged detection efficiency of each device. !Consult Chapter 4 of the January 1999 release of the ACIS calibration !report for a full explanation of the assumptions, model, best-fit model !parameters, probable errors, and limitations inherent !in these model predictions. ! ! !Intended use: !These files provide a higher-spectral-resolution version of the quantum !efficiency data released by MIT CSR in August, 1998, and have been released !primarily to aid in analysis of Transmission Grating Spectrometer data. !These data should support reasonably accurate, broadband counting rate !estimates in the 0.5-4 keV band for proposal purposes. These files probably !overestimate FI detector quantum efficiency outside of the this spectral !band. Accurate analysis of FI CCD spectra will require spectral !redistribution function data. ! !Because the modelling of the BI detectors is expected to improve !significantly before the launch of AXAF, the BI quantum !efficiency curves released herewith are specifically NOT intended for the !analysis of AXAF data on astronomical sources. ! !Notes/Bugs: !1. These QE curves describe at-launch performance and DO NOT account !for any radiation-induced change in quantum efficiency that occurred !after the launch of Chandra. ! !2. Please read the ACIS Calibration report, release of January 1999, !for a complete discussion of the limitations of these predictions. !Systematic relative errors in the spectrally-averaged absolute efficiency !of the FI detector models may be of order 5% over the 0.4-6 keV. Errors !may be larger outside this band. !Errors in the efficiency of one FI device relative to another should be !considerably smaller than 5%, except possibly at energies above 6 keV. !Systematic Errors in the predicted absolute efficiency of the !BI devices may be as large as 25% below 1.5 keV. ! !3. Typical estimated errors as a function of energy for FI devices !was released separately in the file s2_w182c4r_effrange_898.qdp. ! !4. The quantum efficiency in the August 1998 release is sampled on a fixed !energy grid of 0.01 keV spacing between 0.100 and 11.990 keV. This sampling !may be too coarse just above the characteristic edges of nitrogen, oxygen !and silicon, where fine structure has been measured on scales of a few eV. !The July 2000 release has a finer energy grid of 0.2 eV which should be !sufficient resolution near the absorption edges. This finer grid !oversamples the measurements of the absorption edge structure. ! !5.These predictions are intended to represent the spatially averaged !quantum efficiency of each ACIS device. Generally, !quantum efficiency of unradiated FI devices is uniform over the device !within +-5% at all energies below 6 keV. Spatial variations in !quantum efficiency in the BI chips !may be as large at 20%. See the January 1999 release of the !ACIS calibration report for details. ! !6. The BI quantum efficiency estimates are based on a single deadlayer model !for both BI devices, but the two models have !different depletion layer thicknesses. Thus, below about 1 keV, the !predicted efficiencies are identical for the two BI chips. The BI detector !S3 is more efficient than the BI detector S1. ! !7. The data in the files are replica files in !/varda/d0/cgrant/qe_0700/ as of 2000 Jul 24 12:45 (for all chips) ! !8. The BI chip QE curves (for S1 and S3) were revised in 08/04. The !new data are presented here.