lect11 - UCF Physics: AST 5937/4932: (Advanced)...

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UCF Physics: AST 5937/4932: (Advanced) Astronomical Data Analysis Fall 2007 Lecture Notes: 11. Infrared Arrays, Sky, and Corrections 1 Check in: 2:00 — 2:10, 10 min Homework must run or 50% off per problem If you are stuck, comment out stuff that doesn’t run or use fake numbers to get it to run, and say so in a comment. HW5 status. ..need extension to Thursday? DPS Questions before we start? 2 Infrared Arrays: 2:10 — 2:30, 20 min Can dope Si so it is sensitive in visible and still act as CCD Need other materials to be sensitive at long wavelengths InSb λ < 5 μ m HgCdTe λ < 2.4 μ m HgCdTe λ < 10 μ m Si:As λ < 28 μ m Si:Sb λ < 40 μ m HgCdTe QE curve 01irqe.png Most IR materials can’t work as semiconductor like Si CCDs Also, the background can be high in the IR Air, telescope, dome, and camera can emit in IR brighter than astronomical sources “Background limited” sources fill wells fast, so need to read out up to 1 kHz CCD takes several seconds to read Solution: IR absorbing layer connected to Si multiplexer Indium bump bonds connect them 02irbump.png Each unit cell read out directly in turn to amplifier: no charge motion across chip Often have many amplifiers, each reading quadrants or every 4th row, etc. 1
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Huge read noise, up to 2000 e - Can measure voltage on each unit cell diode more than once: non-destructive reads (NDR) Correlated multiple sampling reduces read noise by NDR Trade-off between read speed and noise: CCD slow and accurate, multiplexer fast and noisy
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lect11 - UCF Physics: AST 5937/4932: (Advanced)...

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