| 摘要 |
The invention relates to a miniature X-ray source device connected to a distal end of a guiding wire for insertion towards a desired location within an animal body for effecting radiation therapy, said X-ray source device at least comprising a vacuum tube containing a cathode and an anode spaced apart at some distance from each other; emitting means for emitting free electrons from the cathode; electric field generating means for applying during use a high-voltage electric field between said cathode and said anode for accelerating said emitted free electrons towards said anode; a getter material located in a high-voltage electric field free region in said vacuum tube; wherein said vacuum tube being at least partly transparent to X-ray radiation emitted by said anode. It is necessary to locate the getter material inside the vacuum tube at a location, where no electric field between the anode and cathode exits. An essentially electric field free location of the getter material is required as therefore the getter would not present any internal electrical problems associated with surface arcing or breakdown. To this end, in order to benefit from the use of a getter material inside the vacuum tube for improving the vacuum level inside as well as avoiding any electrical problems as mentioned above and to obtain an improved miniature X-ray tube source device having reduced constructional dimensions according to the invention said cathode is arranged for shielding said getter material from said high-voltage electric field.
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