| 摘要 |
PURPOSE:To make it possible to pick up a huge amount of ion beams, by furnishing a plain grid kept at the negative potential to an ion rejector, a DC power source to keep the plain grid negative, and an electromagnetic coil a DC magnetic field is applied parallel to the central axis of an electron acceleration grid surrounding the ion rejector concentrically. CONSTITUTION:After the inside of an envelope 6 is evacuated throughly, a filament 1 is heated by a heating power source 8, and thermions 2 are emitted. The thermions 2 are accelerated toward an acceleration grid 21 and pass through the next of the electron acceleration grid 21. The thermions 2 flow further to an ion acceleration grid 22, but they lose the speed gradually, stop finally, turn back their direction, and begun to be accelerated again toward the electron acceleration grid 21, because a deceleration electric field to the thermions 2 is composed at the space between the ion acceleration grid 22 and the electron acceleration grid 21. While the thermions 2 fly in the space, they strike the gas molecules to ionize them and produce a plasma. Since the injection efficiency of gas molecules by the electron impact is maximum within a specific area where the kinetic energy of the thermions 2 is maximum, a huge amount of plus ions are generated before and after the thermions stop.
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