Author: Thoma, C.H.
Paper Title Page
WEPC044 Minimizing Beam Motion in a Long-pulse Linear Induction Accelerator 2109
  • C. Ekdahl, E.O. Abeyta, J.B. Johnson, K. Nielsen, M.E. Schulze
    LANL, Los Alamos, New Mexico, USA
  • T.P. Hughes, C.H. Thoma
    Voss Scientific, Albuquerque, New Mexico, USA
  • C.-Y. Tom
    NSTec, Los Alamos, New Mexico, USA
  Funding: This work was supported by the US National Nuclear Security Agency and the US Department of Energy under contract DE-AC52-06NA25396.
The Dual Axis Radiography for Hydrodynamic Testing (DARHT) Facility at Los Alamos uses two linear induction accelerators (LIAs) for flash radiography of explosively driven experiments from orthogonal viewpoints. The DARHT Axis-II long-pulse 1.8-kA, 16.5-MeV LIA is unique. It has a beam pulse with a 1600-ns flattop during which the kinetic energy varies < 2%. During this flattop, a kicker cleaves out four short micro-pulses, which are focused onto a high-Z target and converted to bremsstrahlung for multi-pulse flash radiography of the experiments. Asymmetric injection of the beam into the solenoidal focusing field, small temporal variations in accelerating potentials, and slight cell misalignments cause the beam position to wander during the flattop. This is undesirable for radiography, because it causes a displacement of the four radiographic source spots. Since the specific energy deposition from each micro-pulse can vaporize target material, succeeding pulses impact an asymmetric object causing a distortion of the source spot. This presentation will review the physics of the beam motion and the tuning procedures we have optimized to minimize the number of shots required.