Solar-B EIS Preliminary Design Review 6-7 July 2000 CCD Camera Design Chris McFee Mullard Space Science Laboratory

Solar-B EIS Preliminary Design Review 6-7 July 2000

CCD Camera Design

Chris McFee

Mullard Space Science Laboratory


Introduction

• Science drivers for CCD camera design;• CCD features;• Camera Mechanical Design;• Camera Electronic Design;• Camera Design Trade Offs;• Challenges;• Test Plan and Facilities;


CCD Camera Assembly

The Camera Assembly consists of:

• Focal Plane Assembly (FPA).– Two CCDs at focal plane;– Mechanical mounting of CCDs at focal plane;

• Read Out Electronics.

Three Flight Model CCDs procured with option for further CCDs.

Three Engineering models and six Commercial Devices.


CCD Camera Requirements

Heading Requirement Camera Implications

Spectral resolution High CCD pixel size 13.5µm.

Minimisation of charge transfer inefficiency.

Minimisation of the effects of radiation induced dark noise.

Spatial resolution Equal to or less than 2” CCD pixel size 13.5µm.



Heading Requirement Camera implications

Temporal Resolution

High temporal resolution for both imaging and spectroscopy

Readout speed of 500 kpixels/s.

On chip windowing.

Provision of dump drain.

Wavelength range Two wavelength ranges

Two CCDs.

Backthinned to maximise QE



Heading Requirement Camera Implications

Read out Read out fractions of the CCD

Windowing will be implemented

Read out in fractions of a second

Readout speed of 500 kpixels/s

On chip windowing

Provision of dump drain


CCD features

• Marconi (EEV) 42-20;• Size – 2048x1024 (13.5µm square pixels);• MPP device (dark noise ~ 300 e/p/s @ +20C);• Basic backthining process - ~80% QE;• Electronic readnoise ~ 5/6 electrons;• Full well - ~90k electrons (~7000 photons);• Two readout amplifiers per CCD.


CCD Camera Mechanical design

• CCDs mechanically supported at Focal plane;• CCDs bonded to individual invar plates;• These invar plates then attached to backplates built at MSSL;• Can be moved in two dimensions for alignment;• CCDs connected to ROE by short cable to minimise noise

pickup.


CCD Camera Design

• Operating temperature -55 °C;• CCD can be heated to +30 °C to remove contamination; • Three phase clocking;• Up to two windows per CCD;• Gain ~ 5.5 electrons per DN;• Binning in spatial and spectral direction;• Dumping of unwanted lines;• Programmable voltages to minimise the effects of ionising

radiation damage;• Overclocking for testing, offset bias determination, etc.• Stim patterns for testing;• Flat fielding/Pre flash LEDs.


CCD Camera Design

• Status monitoring.– CCD temperatures;– Current monitoring of supply lines;– Voltage monitoring of supply lines;– Monitor voltage of substrate bias, reset drain bias and output

drain bias;– Reflect back register values for check.


CCD Camera Design

Science data via high speed linkCommunication with ICU via LVDS drivers

@ 16 Mbits/s for each data link

Commands and Status information via low speed link @ 9.6 k baud


CCD Camera DesignWindow counters

Imageclocks

Readoutclocks

CCD biasVariable biasVrd, Vod, Vss

CCD 0

CCD 1

Sync

Sample and convert logic

Para

llel

to

Seri

al c

onve

rsio

n

Pre-

ampl

ific

atio

n

AD

C

High SpeedLink

LowSpeedLink

Science data

Commands and status


CCD Camera Design Trade Offs

• Operating temperature– low operating temperature to minimise dark current and the potential effects of radiation damage. But very low temperatures difficult to obtain without major redesign of radiator, requires use of MPP device but this lowers the full well capacity

• Shielding– maximise shielding to minimise radiation damage but this will add mass. Use of programmable voltages minimises the effects of this damage.


CCD Camera Design Trade Offs

• Read Out Rates.– 500 kpixels/s baselined. Faster readouts are difficult to achieve in

current power budget and design and faster readout also increases CCD readout noise;

• On Chip windowing.– Design of electronics is greatly simplified by reducing the number of

windows that are available;

• Mass– Shielding.


CCD Camera Challenges

• Cleanliness – EUV demands extreme cleanliness;– All operations will use at least a class 100 cleanroom or better, high

standards from GOES-SXI programme adopted with great care taken to eliminate molecular contamination;

• Readout speed – current designs 330 kpixels/s;– 500 kpixels/s and 14 bit digitisation challenging but achievable;

• Physically fitting electronics within the ROE box constraints.


CCD Camera Test Plan

• Read out electronics– Verification of correct functionality

– Optimisation of design with CCD

– Read out noise

– Validate grounding

• CCD characterisation– Establish and Monitor chamber cleanliness levels

– Defects, hot pixels, QE

• Integration with spectrometer


Current CCD Camera Test Facilities

• Camera Test Facilities based on Facilities developed for GOES/SXI;– (large amount of redundancy available)


Current CCD Camera Test Facilities

CCD

Focal plane

Assembly

Preamps

Clock level

shifters

Bias Control

box

Control of CCD bias

voltages

Monitor CCD voltages

Control image clocks

PC 500 MHz,128Mb ram

DAC card

CCD bias control

ADC Card

CCD bias monitoring

DMA Card

MSSL built ISA Card

Control of clocking

Receive CCD data via high speed

link (5.2 MHz)

Generate CCD commands via low

speed link (64 kbaud)

Generate bilevel command lines

and receive status lines

Read out

Electronics

Card 1:

CCD bias supplies

Power switching

Amp-cds-adc

Card 2:

Clock pulse generator

Card 3:

Interface to PC

(FIFO-PISO-HSL)


CCD Camera Schedule

• CCD Camera completed 20 December 2000;• PM delivery 12 March 2001.


Summary

• Resolution.– pixel size 13.5µm.– MPP device to minimise dark current;

• Temporal resolution.– Readout rate 500 kpixels/s;– Dump drain facility;– On-chip windowing;– Two readout amplifiers per CCD.

Documents

Solar-B EIS Preliminary Design Review 6-7 July 2000 CCD Camera Design Chris McFee Mullard Space Science Laboratory