Patent ID: 8498380
Filing Date: 2013-07-30
Classification: H01J

Abstract:
1. An X-ray tube of the rotary-anode type, comprising: a rotating anode having an X-ray emitting surface comprising a target area that includes a focal spot; a cathode comprising a thermionic electron emitter; and an at least temporarily negatively biased main control grid arranged in a vacuum envelope between said emitter and said anode, said X-ray tube further comprising a biased aperture auxiliary grid electrode through which an electron beam emitted by said emitter passes after passing a main control grid and before impinging on said focal spot, said X-ray tube configured for switching said auxiliary grid electrode off by supplying said auxiliary grid electrode with a negative voltage potential, for applying a negative grid cut-off voltage to said main control grid, and for synchronizing said switching with said applying, said grid cut-off voltage being given by a potential difference between said emitter and said main control grid and being more negative than said negative voltage potential.