Current neutralization of nanosecond risetime, high-current electron beams

Methods of achieving current neutralization in fast-risetime (<3 ns) electron beams propagating in low-pressure gas are described. For this investigation, a 3-MV, 30-kA intense beam was injected into a drift cell containing gas pressures form 0.10 to 20 torr. By using a fast net current monitor (100-ps risetime), it was possible to observe beam front gas breakdown phenomena and to optimize the drift cell gas pressure to achieve maximum current neutralization. Experimental observations have shown that by increasing the drift gas pressure (P ≈12.5 torr) to decrease the mean time between secondary electron gas collisions, the beam can propagate with 90% current neutralization for the full beam pulsewidth (16 ns)