An experiment on electron beam transport in an array of wires

We have investigated experimentally the propagation of a relativistic electron beam through an array of parallel conducting wires. Theory and particle simulation predict such an array will provide both charge and current neutralization, allowing beam transport above the drift tube limit. We injected a 60ns, l7kA (12OA/cm/sup 2/ )pulse of 1.4 MeV electrons into an array of 1 m long wires spaced 1 cm apart, filling a hexagon 15 cm across. Arrays have been tested with 12 mil diameter copper wire, 3 mil stainless steel wire, and 12 mil copper wires terminating on an insulated, segmented beam dump. B probes and streak camera data show that 67% of the current is transported in the case of the stainless steel array. The copper wire array transported electrons for 20ns only. The beam is injected with a 250 mrad divergence, and the transported beam has a divergence of less than 100 mrad. Follow-up experiments are to use thinner wires to improve both the propagation and divergence of the beam.