| 摘要 |
In rotating anode X-ray tubes it has not been the practice to provide anode cooling because of problems in arranging coolant flow. A further problem which has arisen, particularly in tubes for computerized tomography which should have precisely defined focal spots, is off-focus radiation apparently resulting from back scattered electrons hitting the tube target away from the focal spot. It is here proposed to provide a rotating anode X-ray tube with a shroud surrounding and close to at least part of the anode. This is extended towards the electron gun with an aperture through which the electron beam travels and an X-ray emissive window. The shroud collects back scattered electrons and can also be fluid cooled. The window provides some collimation and the edges can be shaped to restrict the focal spot as viewed away from the main X-ray beam.
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