CCD RAIN PHOTONS VERTICAL CONVEYOR BELTS CCD COLUMNS

CCD RAIN (PHOTONS) VERTICAL CONVEYOR BELTS (CCD COLUMNS) BUCKETS (PIXELS) HORIZONTAL CONVEYOR BELT MEASURING CYLINDER (OUTPUT AMPLIFIER) (SERIAL REGISTER) 1

CCD Incoming photons Ø All astronomical CCD’s are thin, backside illuminated Ø Consumer CCD’s are thick, frontside illuminated Anti-reflective (AR) coating p-type silicon n-type silicon Polysilicon electrodes Incoming photons 15 mm p-type silicon n-type silicon 625 mm Silicon dioxide insulating layer Polysilicon electrodes 2

CCD Photomicrograph of a corner of an EEV CCD. 160 mm Bus wires Serial Register Read Out Amplifier Edge of Silicon Image Area The serial register is bent double to move the output amplifier away from the edge of the chip. This useful if the CCD is to be used as part of a mosaic. The arrows indicate how charge is transferred through the device. 3

CCD 1 2 3 4

CCD Image area Metal, ceramic or plastic package Connection pins Gold bond wires Bond pads Silicon chip On-chip amplifier Serial register 5

CCD The diagram shows a small section (a few pixels) of the image area of a CCD. This pattern is reapeated. Channel stops to define the columns of the image Plan View One pixel Cross section Transparent horizontal electrodes to define the pixels vertically. Also used to transfer the charge during readout Electrode Insulating oxide n-type silicon p-type silicon Every third electrode is connected together. Bus wires running down the edge of the chip make the connection. The channel stops are formed from high concentrations of Boron in the silicon. 6

CCD Camera Thermally Insulating Pillars Electrical feed-through Vacuum Space Pressure vessel Pump Port Telescope beam Face-plate CCD Focal Plane of Telescope Optical window . . . CCD Mounting Block Thermal coupling Boil-off Nitrogen can Activated charcoal ‘Getter’ 7

CCD Camera CCD Retaining clamp Temperature servo circuit board Aluminised Mylar sheet Gold plated copper mounting block Top of LN 2 can Platinum resistance thermometer Pressure Vessel ‘Spider’. The CCD mounting block is stood off from the spider using insulating pillars. Location points (x 3) for insulating pillars that reference the CCD to the camera face-plate Signal wires to CCD 8

CCD Mosaic 9

CCD Ø Buried channel MOS type p-n type 10