Method for controlling the electron current in an x-ray tube, and x-ray system operating according to the method
AssigneeSiemens Aktiengesellschaft
InventorsErich Hell, Peter Schardt
Life of this patent
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Abstract
In a method and x-ray system for controlling the electron current in an x-ray tube emitted from a continuously heated electron emitter with an allocated focussing electrode to an anode, the potential of the focussing electrode is pulsed between a conducting-state voltage, selected dependent on the desired size of the focal spot and/or the tube voltage of the electron beam on the anode, and a blocking voltage interrupting the electron current to the anode, the pulsewidth being modulated to control the electron current.
Claims20
A method for controlling an electron current in an x-ray tube, comprising the steps of:
- continuously heating an electron emitter during operation of an x-ray tube containing said electron emitter to emit an electron beam from said electron emitter;
- causing said electron beam to strike an anode in said x-ray tube at a focal spot on said anode, said focal spot having a focal spot size, said anode thereupon emitting x-rays;
- producing a tube voltage across said electron emitter and said anode, said tube voltage having a tube voltage amplitude;
- disposing a focussing electrode at said electron emitter, said focussing electrode having a focussing field which interacts with said electron beam, said focussing electrode being at a focussing electrode potential;
- pulsing said focussing electrode potential at a pulse frequency between a conducting state voltage which allows passage of said electron beam through said focussing electrode and a blocking voltage which interrupts said electron beam to control an electron current associated with said electron beam;
- and
- selecting said pulse frequency dependent on both said focal spot size and said tube voltage amplitude.
An x-ray system comprising:
- an x-ray tube containing an electron emitter which emits an electron beam, an anode on which said electron beam is incident at a focal spot having a focal spot size, said anode emitting x-rays from said focal spot;
- means for continuously heating said electron emitter during operation of said x-ray tube for causing said electron emitter to emit said electron beam;
- means for producing a tube voltage across said electron emitter and said anode, said tube voltage having a tube voltage amplitude;
- a focussing electrode disposed in said x-ray tube at said electron emitter having a focussing electrode field which interacts with said electron beam, said focussing electrode being at a focussing electrode potential;
- and
- control means for pulsing said focussing electrode potential with a modulated pulse frequency between a conducting state voltage which allows passage of said electron beam through said focussing electrode and a blocking voltage which interrupts said electron beam, for controlling an electron current associated with said electron beam dependent on both said focal spot size and said tube voltage amplitude.
Dependencies are inferred from the claim text.