| 摘要 |
PURPOSE:To prevent the occurrence for a leak current from a getter material, by installing a recessed part, which is not opposed to a magnetic pole and the anode, in an upper end shield of a magnetron cathode structural. CONSTITUTION:In an upper end shield 2, there is provided with a recessed part 2 at the opposite side to the filament fixed side, and a getter material 6 is tightly attached to the inside of a recessed part 2 so as not to oppose a magnetic pole 9 and a vane 7. According to such like constitution, the getter material 6 absorbs a large quantity of gas, and a surface state becomes rough, coming into the state that cold emission is liable to go out, whereby even if high voltage is impressed between the cathode and the anode, the getter material is not opposed to the magnetic pole 9 and the vane 7 so that field strength among the getter material 6, magnetic pole 9 and the vane 7 becomes very weakened, thus a leak current from the getter material 6 is prevented.
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