'Focus' p2 Searchterm 'Focus' found in 4 terms [ • ] and 9 definitions [• ]Result Pages : •
X-ray tubes are devices for the production of x-rays. X-ray tubes consist of an evacuated glass vessel and two electrodes. An electrical current with very high voltage passes across the tube and accelerates electrons emitted by thermionic emission from a tungsten filament (cathode also called electron gun) towards the anode target. The electrons collide with the anode and this deceleration generates x-rays (bremsstrahlung). The high vacuum allows the electron beam an unimpeded passage. The electron beam heats the anode (usually copper), which is cooled by water to prevent melting. A copper target emits x-rays with a characteristic wavelength. Other used metals soften or harden the x-ray beam. The x-rays pass through a very thin beryllium (Be) foil. This beryllium window absorbs a high amount of the elastically scattered electrons (produced by the target) and allows the radiation to get out of the tube without substantial absorption. In conventional x-ray tubes, the anode is also the target. In nanofocus and microfocus x-ray tubes, the electron beam is transmitted through a hole in the anode where it is then focused onto a small spot on the target. See also X-Ray Tube Housing, Fine Focus X-Ray Tube, Transformer, Diode, Digital to Analog Converter and Angular Response. • View NEWS results for 'X-Ray Tube' (1). Further Reading: News & More:
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The highest amount of detail that can be shown in an image. Defined by the size of the smallest object that can be conveniently viewed, which for nanofocus and microfocus x-ray tubes is about half the size of the focal spot. •
An electromagnetic lens is designed to focus the electron beam by using a suitable shaped magnetic field. The lens is a symmetric electromagnet consisting of wire coil, magnetic iron yoke and iron pole pieces.
A strong magnetic field is produced by passing a current through the windings. This field acts as a convex lens; converge off axis rays back to focus. Like an optical lens, a magnetic lens is characterized by focal length and can be altered by changing the strength of the current.
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Compton scattering is the deflection of gamma- and x-ray photons by electrons. See also Compton Continuum, Compton Effect, Air Kerma, Filter Grid, Focused Grid, Grid Efficiency, and Compton Arthur Holly. Further Reading: News & More:
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Cryotherapy (also called cryoablation or cryosurgery) uses extreme cold for the treatment of disease. A cryoprobe applies the cold to the selected anatomic area, for example the prostate. See also Brachytherapy, RF Thermal Ablation, High Intensity Focused Ultrasound and Prostate Ultrasound. Result Pages : |