Transport measurements in a two-stage proton linear induction accelerator

An experimental study of the transport of a 1 MeV, 6 kA, 50 ns annular proton beam in several confinement geometries is in progress. Carbon activation and Faraday cup arrays are employed to measure proton density and current density respectively. Radial current profiles show that significant beam focusing occurs when the beam is injected through a half-cusp into a 1.4 T solenoidal magnetic field. The strength of this focusing increases with beam current. At beam currents < 1 kA the authors measured transport efficiencies of up to 100% across the second accelerating gap (300 kV, 2.5 cm). However, beam divergence is found to increase significantly as the beam traverses this gap. The transport efficiency is reduced at higher beam currents. A full-cusp injection system has been constructed in order to maintain the annular beam profile throughout the system. Transport measurements in this geometry will be presented for both single and two stage operation