A Study of the Properties of a Magnetically-Insulated Ion Diode

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Abstract
The diode mechanism was studied in a magnetically-insulated ion diode producing a proton beam of 7 kA total current with high efficiency (∼40%), having an ion current density exceeding the Child-Langmuir current by a factor of more than 50 and long pulse insulation of the gap (∼850 ns). It was found that electrons in the gap move azimuthally in theEz×Br, direction under the balance of radial forces. Optimization of the azimuthal drift length (∼60 mm) and the uniformity of the anode plasma is possible if the shape of the insulating magnetic field is changed. The ion production efficiency is mainly determined by this length. The ion beam divergence of 1°∼4° is thought to be caused by cathode plasma filamentation and ion space charge in the drift region. It is shown that when titanium hydride is used as the anode material, electron bombardment plays an important role in the anode plasma production.