Auxiliary grid electrode for x-ray tubes
AssigneeKoninklijke Philips Electronics N.V.
InventorRolf Karl Otto Behling
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Abstract
The present invention refers to an X-ray tube of the rotary-anode type which comprises at least one temporarily negatively biased auxiliary grid electrode (119) with an aperture through which an electron beam (115) emitted by a tube cathode's thermoionic electron emitter (111) can pass. As an alternative thereto, the auxiliary grid electrode (119) may also be positively biased so as to enhance electron emission from a thermoionic electron emitter (111). The auxiliary grid electrode may thereby be connected to a supply voltage UAUX of a controllable voltage supply unit by means of a feedthrough cable (120) serving as a feeding line for providing the main control grid (112) with a grid supply voltage UG.
Claims7
A high-power X-ray tube of the rotary-anode type (100), comprising a rotating anode (101), a cathode (103) equipped with a thermoionic electron emitter (111) and an at least temporarily negatively biased main control grid (112) arranged in a vacuum envelope (100a) between the thermoionic electron emitter and the rotating anode, said X-ray tube further comprising a biased aperture auxiliary grid electrode (119) through which an electron beam (115) emitted by the thermoionic electron emitter (111) of the X-ray tube's cathode (103) passes after passing the main control grid (112) and before impinging on a focal spot (109) in a target area of the tube anode's X-ray emitting surface.
The method according to claim 3,
- wherein the process of switching the aperture auxiliary grid electrode (119) off by supplying it with a negative voltage potential (UAux) such as proposed in claim 5 is synchronized with an application of a negative grid cut-off voltage (Uco) to the X-ray tube's main control grid (112), said grid cut-off voltage being given by the potential difference between the tube cathode's thermoionic electron emitter (111) and the main control grid (112).
Dependencies are inferred from the claim text.