Electron-Bombarded Charge-Coupled Devices

Electron-bombarded charge-coupled devices (CCDs) are a relatively new development in which photons are detected by a photocathode in a manner similar to an image intensifier. Instructions for operation of the tutorial appear beneath the applet window.

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Photons (yellow) impinging upon the surface of the photocathode liberate photoelectrons (red), which are accelerated by a high voltage gradient and impact on the back side of a CCD. Use the Gain slider to control the voltage supplied to the photocathode and, hence, the intensity or number of photoelectrons emitted by the photocathode.

The high-energy electrons that strike the CCD generate multiple charges resulting in a modest gain of a few hundred. The advantages of this device over a cooled, slow-scan CCD are the additional gain and accompanying speed; the main disadvantages are the lower quantum efficiency of the photocathode and diminished dynamic range.

Contributing Authors

Kenneth R. Spring - Scientific Consultant, Lusby, Maryland, 20657.

John C. Long and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.