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NOT CCD4 (HiRAC), details:

Notices, Properties, Oxygen soaking, Literature, Links.


25 Feb 1999: The flat field of this CCD appears to have changed as of 15th Feb 1999. Because the CCD requires O2 flooding as part of the backside passivation, the flat field is not absolutely stable from run to run (or, more precisely, from cool-down to cool-down). Normally, any changes will be invisible except upon dividing one run's flat field by that of another and even then the effects may be negligible. However, as of February 1999, an unusual pattern has appeared in the upper right corner of the CCD flat field. The quantum efficiency of the region is reduced by approximately 10%. Its qualitative appearance suggests that it may be the result of contamination of the detector. At the time of writing, we are investigating possible causes. The affected area is small and unlikely to affect observations.

Summary of properties:

Provenance Loral/Lesser
Horizontal pixels 2048
Vertical pixels 2048
Pixel size1 & plate scale 15µ, 0.110"/pixel
Readout noise approx 6 e-/pixel
Conversion factor ~1 or ~3 e-/ADU
Nonlinearity ~0.7%, Amp A., High gain
Readout time TBM
MTF Unknown (should be similar to CCD7)
QE: 350, 400, 500, 600, 700, 800 nm68, 90, 93, 90, 70, 60 %
CTI (H, V) <1×10-6, 3×10-6
Cosmetic quality 5 bad columns, 8 traps
possible contamination damage, top-right corner.
Full well 90,000 electrons
Passivation technology Ultrathinned, PPtF, O2 soak

Notes & Legend:
1: Pixels have very slightly different dimensions in the horizontal and vertical directions.
TBM = To Be Measured

Oxygen Soaking

Because this device uses the PPt passivation technology, it requires soaking in oxygen before cooling in order to achieve the best possible QE sensitivity and uniformity. Occasionally, this can fail. In this case, the flat field will be very non-uniform with a number of sensitive patches distributed over a much reduced overall sensitivity. For sample images, look here. Normally this will be caught before the observer arrives at the telescope to use the instrument.

Other Literature:


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