Self-magnetic-field-enhanced ion diode

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Abstract
An intense ion source has been developed utilizing an ion diode that partially suppresses electron flow using the self-magnetic field of the diode current. This is an extension of a diode class known as pinch reflex ion diodes. In this case the diode was coupled to the particle beam fusion accelerator and was configured in two different cylindrical designs. The first pinch ion diode was a straight, 42-cm-diam cylinder and the second, Obi, was a focusing, 26-cm-diam, aspheric barrel. In the Obi diode a central gas cell provided current-neutralized beam transport. In addition, the accelerator was run in a low-voltage, 0.8 MV, and a high-voltage, 2.0 MV, mode. The best results showed that the Obi diode produced 3 TW of protons at 34% efficiency in the high-voltage mode. We present an analytic model of ion efficiency, compare various diode impedance models, and discuss beam divergence mechanisms. The limitation of this ion source as a fusion driver is presently the 2–3° divergence that we measure using a shadow-box technique. A companion paper contains numerical simulations and further analytic modeling.