Glossary of terms used on this site
C
- Characteristic radiation
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The discrete part of the X-ray spectrum*. The electrons suddenly decelerate upon colliding with the material target and knock out electrons from the inner shell of the target atoms. As a result, electrons from higher energy levels fill up the vacancies and X-ray photons are emitted to compensate for the difference in energy between the two shells. The wavelength distribution of the characteristic radiation varies from material to material- different anode materials create more or less high-energy X-rays, thus directly influencing their capability to pass trough material.
- Contrast
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Radiographic contrast describes the differences in photographic density in a radiograph. The larger the difference in thickness or density between to areas of the subject, the larger the difference in radiographic density or contrast, the more visible features become. Contrast is caused by the fact that different parts of the object absorb X-rays differently. How great a difference in radiation absorption is necessary depends on the detector. With two parts of an object with radiation intensities I[A] and I[B], the difference in contrast is defined as 2*| I[A] � I [B] | / ( I[A] + I [B] ). As a rule of thumb, a difference in radiation absorption of 2% (0.5% for a digital detector) is needed in order for an image intensifier to produce a visible image. Moreover, contrast depends on the wavelength of the primary radiation.
- Coolidge, W.D.
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Inventor of the Coolidge tube, also called hot cathode tube (1913). It is still used today, since most X-ray tubes used today are based on the design of the Coolidge tube.
- Cosslett, V.E.
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This British physicist was the first to build a microfocus X-ray tube, based on a suggestion of M. v. Ardenne, and to use it in his �Shadow X-ray microscope� in 1951 (Nature 10, 1951, pp 24).