Intense ion beam generation with an inverse reflex tetrode (IRT)

摘要

An inverse reflex tetrode (IRT) for producing an intense pulsed beam of ions includes a real cathode having a curved or conical surface which is substantially transparent to the ions; first anode and second anode, or grid, which are spaced apart and are at the same potential, the first anode being between the real cathode and the second anode and having a curved or conical surface approximately parallel to the surface of the real cathode, and also being formed from a dielectric material such as polyethylene; a curved or conical hollow anode stalk which supports both anodes; and a virtual cathode which is formed by electrons that are emitted by the real cathode and pass through the first anode. The real cathode and first and second anodes are enclosed in a vacuum chamber and are immersed in an applied external magnetic field. The IRT receives an electrical pulse from a high-voltage pulse generator. The real cathode emits electrons which accelerate toward the first anode, pass through the first anode and form a virtual cathode between the first and second anodes. Most of the electrons oscillate between the virtual cathode and the real cathode and form a plasma sheath on the surfaces of the first anode. Some ions from the plasma propagate toward the second anode, and some ions propagate toward the real cathode. The ions arrive at the second anode with zero velocity, while the other ions pass through the real cathode and form a propagating ion beam.