Fluctuations and nonuniformity of the ion beam current and electron flow in a long-pulse, applied B/sub r/ magnetically insulated ion diode

The low-frequency fluctuations (10--200 MHz) and spatial nonuniformity (2--20 mm) of ion beam currents and electron flow have been studied for a long-pulse (insulation time approx.1 μs) intense ion beam source. The total ion current was > or approx. =5 kA, the ion energy was approx.70 keV, and the total ion output was approx.1 x 1016/pulse. The fluctuations and nonuniformity of the electron flow were measured using x-ray emission from the anode and magnetic probes. Those were closely correlated to the fluctuations and nonuniformity of the ion beam. With a high-current, low-voltage diode, measurements indicated that the ion beam characteristics were caused by a low-frequency instability. One possible candidate for this instability is the cathode-plasma filamentation which has been found using an image converter camera