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FOS1 Parameters

Device Identification

Chip name FOS1

Year of manufacture: 1997

Serial number: FT512 w11-8

First light on La Palma: Feb. 1998

Description: Thinned backside illuminated with passivated platinum surface.

Operational Characteristics

Measurements made on
Linear to(ADU)
Readout time(s)
Binning - NB when binning is selected the readout speed is TURBO regardless of the readout speed selected.

Vertical CTE                                               0.999994

Horizontal CTE                                           0.999996

Physical Characteristics

Pixel Scale                                                   ? arcsecs/pixel

X Pixel size                                                  15 microns

Y Pixel size                                                  15 microns

X size in pixels of digitised area                    528

Y size in pixels of digitised area                    1124

X size of useful imaging area                     512

Y size of useful imaging area                     1024

X start of useful imaging area                    1

Ystart of useful imaging area                     1

LN2 capacity of cryostat                            2.5 litres

Operational Parameters

Flooding type

Passivated Platinum Process - The high QE of this device in the blue is due to the passivated platinum surface treatment of the CCD. This treatment is particularly prone to surface contamination of the chip such as will occur if the LN2 supply runs out with the chip still cold. If the camera is to be warmed up it is essential therefore that the CCD temperature servo be set to an elevated temperature prior to LN2 exhaustion. If the surface does become contaminated, it will show itself as a loss of blue sensitivity and a very mottled flat field response. The activity of the Platinum treatment can be restored by the following steps :

1) Warm up the camera.

2) Pump for one hour.

3) Backfill the camera through the vacuum pump. This will bathe the chip in dry air since the pump should contain a moisture trap.

4) Leave for one hour, then re-pump for at least a further hour.

5) Refill with LN2 immediately after disconnecting the vacuum pump.

Controller Hardware Modifications        CDS Card gain reduced, R5 changed to 6K7

Operating temperature                             173K

Preferred amplifier                                     B giving 8.6e noise.( A is the backup giving 8.9 e noise,, C & D are unusable )

Network name                                           CCD1

Anti blooming available                            no

Measured Characteristics

Quantum Efficiency - Sky blue line FT512 W10-7

Dark current   1 electron/pixel/hour @ -107 Degrees C after 24 hours in the dark and after being switched on for 16 hours.

Point spread function  - The CCD suffers from a poor PSF particularly at the blue end of the spectrum. Photoelectrons diffuse sideways a considerable distance resulting in effective pixel sizes similar to the old GEC chip used in FOS. The FWHM is approximately 1.8 pixels @ 820nm, 2.5 pixels @ 440nm.

Full well bloom limit  50000 e

Chip flatness   Approximately +/- 1 micron

Cosmetics - No bad columns, very clean.  Thinning defect rounds off the image area near amplifier D, not a serious problem.  Some vertical streaks visible in flats near amplifier A.  Slight rise in bias in first few columns.

Cosmic Rays  600 events per hour

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Last modified: 21 November 2010