Search for Defocusing During a Single Pulse of a 2 kA Relativistic Electron Beam Due to Ions Accelerated from a Target

Lauer, E J ; Caporaso, G J ; Chambers, F W ; Chen, Y-J ; Falabella, S ; Guethlein, G ; McCarrick, J ; Richardson, R ; Sampayan, S ; Weir, J

Lawrence Livermore National Laboratory

关键词: Dielectric Materials;    99 General And Miscellaneous//Mathematics, Computing, And Information Science;    43 Particle Accelerators;    Lanl;    36 Materials Science;   

DOI  :  10.2172/15002787
RP-ID  :  UCRL-ID-150026
RP-ID  :  W-7405-ENG-48
RP-ID  :  15002787

美国|英语

来源: UNT Digital Library

【 摘 要 】

The DARHT accelerator will deliver several intense relativistic electron beam pulses to an x-ray conversion target during a few microseconds. Plasma from the target can cause a partial neutralization of the vacuum self-Er field resulting in an unacceptably large beam radius at the target. The Livermore group has been developing barrier foils to block the plasma from moving upstream. Positive ions accelerated upstream from the foil in the self-Ez field during a single pulse could defocus the beam. In May, 2001 LANL used a sensitive ''two foil'' experiment to search for such effects. They measured significant time dependent effects using conducting foils (1). In January, 2002, the Livermore group repeated the experiment using the ETA II accelerator. We expected to see similar effects and planned to collect data that we could model. We saw no significant effect from conducting foils unless the beam radius was small enough to damage the foil. The reason for the different results has not been explained and is still being investigated. Possibilities have to do with the longer pulse length at LANL, (60 ns compared to 40) or with the higher energy at LANL, (20 Mev compared to 5.7) We also did some tests on dielectric targets where there is a strong effect to test our techniques.