TRANSVERSE BEAM MOTION ON THE SECOND AXIS OF THE DUAL AXIS RADIOGRAPHIC HYDRODYNAMIC TEST FACILITY*

The accelerator on the second-axis of the Dual-Axis Radiographic Hydrodynamic Test (DARHT-II) facility [1] will generate a 20 MeV, 2-4 kA, 2 m s long electron beam with an energy variation £ – 0.5%. Four short current pulses with various lengths will be selected out of this 2 m s long current pulse and delivered to an x-ray converter target. The DARHT-II radiographic resolution requires these electron pulses to be focused to sub-millimeter spots on Bremsstrahlung targets with peak-to-peak transverse beam motion less than a few hundred microns. We have modeled the transverse beam motion, including the beam breakup instability, corkscrew motion [2, 3], transverse resistive wall instability [4] and beam induced transverse deflection in the kicker system, from the DARHT-II injector exit to the x-ray converter target. Simulations show that the transverse motion at the x-ray converters satisfies the DARHT-II radiographic requirements.