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CCD Detectors in High-Resolution Biology

CCD Detectors in High-Resolution Biology. Jian Guan 6-28-2013. Overview . Some Chemistry Concepts What is CCD? How does CCD work? Structure of CCD Principle of CCD Operation Pixel Size calculation. Some Chemistry Concepts. 1.12ev. +. 3.55ev. Silicon Crystal. What is CCD?.

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CCD Detectors in High-Resolution Biology

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  1. CCD Detectors in High-Resolution Biology Jian Guan 6-28-2013

  2. Overview • Some Chemistry Concepts • What is CCD? • How does CCD work? • Structure of CCD • Principle of CCD Operation • Pixel Size calculation

  3. Some Chemistry Concepts 1.12ev + 3.55ev

  4. Silicon Crystal

  5. What is CCD? Willard.S Boyle George Elwood Smith

  6. How does CCD work?

  7. Structure of CCD

  8. Principles of CCD Operation Direct detection, well… • More than enough • Damage • Interference from X-ray

  9. Indirect Detection is much more acceptable: Electron energy conversion into light • high conversion efficiency into visible radiation, • reasonably short and well-defined decay time of the emitted scintillation, • phosphor output wavelength matched to CCD sensitivity (which has a maximum at ~700 nm), • resistance to radiation damage, • a convenient, reproducible method of depositing a thin layer of phosphor on a flat surface. Strong electron P20: zinc cadmium sulphide doped with silver P43: gadolinium oxy-sulphide doped with terbium

  10. Optical coupling: Lens or Fibre optics Lens coupling Fibre optics

  11. Readout and analog-to-digital At the output Stage The charge in Pixel is transferred to a capacitor Amplifier and analog-to-digital converter Convert charge to 12 bits or 16 bits resolution (Digitalization)

  12. Noises • Dark current noise • Readout noise • Spurious events due to X-rays or cosmic rays Temperature-dependent keep cold Faster readout, more than one read out node Software algorithm

  13. Electron diffraction applications

  14. Pixel Size Calculation Calculation of Pixel Size from a CCD Image Actual pixel size Get the pixel size information from the Digital Micrograph program Save CCD image in DM3 file format  Pixel size = Magnification If not:

  15. For Example Apogee AP7p CCD Pixel Array: 512 x 512 pixels Array Dimensions: 12.3 mm x 12.3 mm Pixel Dimensions: 24 micron square Actual pixel size Pixel size = Array dimension Actual pixel size = = 12.3/512 = 24 micron = 240,000 Angstrom Magnification Pixel arry Magnification = 100,000 = 2.4 Angstrom

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