NOT CCD4 (HiRAC), details:
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:
|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 nm||68, 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
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.