Proposed New Fies CCD
The proposed new CCD for FIES is either the E2V Technologies
CCD203-82 (LAMOST)
 or the
CCD231-84.
The CCD203-82 is back illuminated, 4096 x 4096 12μm pixels and comes in
either standard silicon or deep depleted with a range of alternative AR
(anti-refection) coatings.
The alternative CCD231-84 is also back illuminated, 4096 x 4096 but has
the larger 15μm pixels, comes with the same silicon and coating choices as
the CCD203-82 but has a better specified read-noise of 2e-
against 3e- for the CCD203-82 at <50Kpxls.
Both the above devices have similar architecture with 4-phase vertical
(column) clocks and 3-phase serial registers located at the top and bottom of
the chip. Each serial register has two outputs. The CCD can be read from
any combination of the readout ports depending on the capability of
the controller.
At the ESO Detector Workshop 2009 a poster paper was presented on the
MUSE Detector System
which uses the CCD231-84 device. The MUSE CCDs are deep depletion, have
a graded AR coarting and are used in an identical application to FIES,
fixed echelle spectrograph type instrument. The MUSE paper showed a
couple of useful plots of the peak QE for three devices and the PSF
dependancy of the collecting phase
voltages (Vc)1 and the number
of phases you actually integrate under.
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Measured peak QE for three CCD231-84 Devices with graded AR coating
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Measurements of the variation of the PSF wrt the phase voltage (Vc)
and the number of active phases integrated under
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1 Note:
A confusing item is the definition of Vc.
E2V sets zero voltage at the lowest potential and that is the low voltage of
the parallel clocks. Virtually everyone else (including ESO) sets zero voltage
at the substrate voltage. Thus when Vc = +2V, it is respect to
substrate which is set to zero voltage and the clocks vary from low of -8V
to high of +2V (i.e. by 10V). E2V on the otherhand say that the low level is
set to 0V (i.e. at E2V's zero potential) and one increases it to +10V
(as shown in the datasheets) for collecting charge. (The E2V typical value for
Vss = +9V.)
A variant on the CCD231-84 but in a Cermaic PGA package is the
CCD230-84
. This
CCD has poorer RON at 4e- and there is no mention
of a deep depletion option but it is believed there is.
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