| 摘要 |
The envelope comprises a window made of material transparent to the radiation emitted by the source that comprises at least one chamber (20, 22, 23) in which can be moved a material impervious to the electromagnetic radiation, the chamber being shaped such that the material impervious to the radiation can be inserted from outside the chamber and that inside the chamber the material impervious to the radiation surrounds a radiation beam passage zone, such that the surface of the beam passage zone vaires according to the volume of the impervious material in the chamber, thus eliminating the extrafocal stray radiation. The invention is useful in X-ray imaging apparatus.
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