单词	X-ray tube
释义	X-ray tube A device for generating X-rays by accelerating electrons to a high energy by an electrostatic field and making them strike a metal target either in a tube containing a low-pressure gas or, as in modern tubes, in a high vacuum. The target is made from a heavy metal, usually tungsten, and is backed by a massive metal anode to conduct the heat away (see illustration showing a liquid-cooled copper anode). The electron beam is produced by heating the cathode by means of a white-hot tungsten filament. A transformer supplies the high voltage, often 100 kV, the tube acting as its own rectifier. On the half-cycles when the target is negative nothing happens. When the target becomes positive, the electrons bombarding it generate X-rays. X-ray tube
随便看	Q-value QCD QED QFD QSG QSO QSS quadratic equation quadrature quality of sound quantization quantum quantum chaos quantum chromodynamics quantum electrodynamics quantum electronics quantum entanglement quantum field theory quantum flavourdynamics quantum gravity quantum Hall effect quantum jump quantum mechanics quantum number quantum optics

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