Time-dependent degradation of an ion-focused ATA beam

Abstract

We have made detailed measurements of the timedependent beam quality of an ATA pulse transported on a KrF laser-photoionized benzene channel. We have found that the tail portion (T > 20-30 ns) of the pulse becomes severely degraded both at high currents (I > 3 kA) and at long transport distances. Non-axisymmetric channel ion motion is suspected as the predominant source of the problem. We discuss various experiments which varied laser properties (timing, fluence, profiles), background ion pressure, and electron beam current in order to study the physics behind this degradation.

Foil Focusing of Electron Beams

“…Both transport techniques are, moreover, subject to beam instabilities, either from cavity modes 3 or from ion motion. 4 An alternative transport technique, first suggested by Adler, 5 is a series of thin conducting foils placed transverse to the beam axis. Foils act like thin electrostatic lenses that focus the beam via image charges.…”