| 摘要 |
PURPOSE:To provide an electron beam with uniform density by supporting each end of a filament with bimetal, and offsetting the longitudinal elongation of the filament central part due to thermal expansion with the warp of bimetal caused by temp. change. CONSTITUTION:Bi-metal 13 has a warp of L/2, where L is elongation of the central part 17c of a filament 17, and thereby absorbs an elongation of L/2. In the process from room temp. to completion of heating, the bimetal 13 follows elongation of the filament 17 and supports it without deflection. In this arrangement, there is no member which hinders thermal expansion of the filament central part 17c in the sectional direction, and the dia. of the filament 17 will be constant at all temps. As the filament central part 17c is free from contact with any other member, the temp. distribution will also become constant. The bimetals 13, 14 are free from deflection at all temps. Thereby an electron beam with uniform density is obtained from filament 17.
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