1. Area Detectors Like film can detect position Like scintillation detector can measure intensity With modern computers can assign hkl from unaligned crystal Must convert pixel intensity to intensity by some sort of integration

2. Image Plates Use a phosphor which emits light proportional to x-ray exposure Very large dynamic range Very low background Large input area Not a “real time” device

3. Rigaku r-axis

4. Image Plate Schematic

5. How IP works

6. Small Molecule IP

7. Schematic

8. CCD Detector The ccd is a standard camera chip Need a phosphor to convert x-rays to light The ccd pixel is a well that converts photons to electrons and stores them. The wells are read out by shifting to special readout wells and using an a-to-d converter

9. Schematic of a ccd

10. Noise Dark Current—stored electrons from dark exposure Can reduce dark current by cooling the ccd. Peltier cooling is frequently used Readout Noise—from moving pixels to counting registers Slower the movement the lower the noise

11. Size More most 1K ccd chips the pixels are too small. Use glass taper to expand the face. Taper introduces a distortion Pixels still to small. Binning—fold 4 pixels into 1 Use large ccd chip 4K

12. Phosphors Thickness is important Too thin and x-rays penetrate Too thick and emitted photons are re- absorbed For Mo radiation phosphor is only about 80% efficient

13. KappaCCD Roughly 1K chip 12 electrons/photon Dark current 0.02electrons/second Read out at 200kHz—noise about 12electrons Pixel size 22.5 x 22.5 micrometers Binned 110 x 110 Readout time about 3 seconds

14. KappaCCD

15. Kappaccd