When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2-kA, 17-MeV electron beam in a 1600-ns flat-top pulse. In initial tests, DARHT-II accelerated beams with current pulse lengths from 500 to 1200 ns full-width at half-maximum (FWHM) with more than 1.2-kA, 12.5-MeV peak current and energy. Experiments have now been done with a 1600-ns pulse length. These pulse lengths are all significantly longer than any other multimegaelectronvolt LIA, and they define a novel regime for high-current beam dynamics, especially with regard to beam stability. Although the initial tests demonstrated insignificant beam-breakup instability (BBU), the pulse length was too short to determine whether ion-hose instability would be present toward the end of a long, 1600-ns pulse. The 1600-ns pulse experiments reported here resolved these issues for the long-pulse DARHT-II LIA.

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The second axis of the dual-axis radiographic hydrotest (DARHT) facility will provide four radiographic images within -1.6 microseconds. This will be accomplished by slicing four short pulses out of a -1.6-microsecond long electron beam produced by the DARHT-II linear induction accelerator and directing them onto a bremsstrahlung converter target. Commissioning of the full 17-MeV configuration the DARHT-II accelerator will begin in spring of 2007 following tests of a new high-perveance (2 kA at 2.5 MV) diode. We will present the results of diode performance measurements as well as initial measurements of the fully accelerated electron beam parameters.