| 摘要 |
The cathode comprises a directly heated emitter with variable emission surface area, which is held by support wires, forming a part of a current supply, whereby the current supplies to the emitter (1) are, at least partially, separately heatable. The support wires carrying the emitter are preferably U-shaped, whereby thighs (6a, 6b) of each support wire are connected respectively with an additional heating current source (UZl, UZ2). The emitter legs (2) of an emitter, preferably formed as flat emitter, are preferably slit, forming respectively two thighs (2a, 2b), whereby the thighs of each emitter leg are connected respectively over an additional current source, and whereby respectively one thigh of each emitter leg is connected to the emitter heating current source (UH).
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