Reduction of energy sweep of the ETA-II beam

The ETA-2 electron beam will be used to drive a high power microwave frequency FEL for plasma heating experiments. For maximum FEL output power the beam energy at the entrance to the wiggler should be within ±1% of the wiggler resonance value. In initial operations the ETA-2 beam energy stayed within this range for a maximum time of less than 13 ns, Much of the energy variation was due to the design of the pulsed power feeds to the of the pulsed power feeds to the accelerator induction cells. A new multicable pulsed power feed design was tested in a shortened version of ETA-2 where it extended the time during which the beam energy stayed within the ±1% limits to greater than 40 ns. These design changes are now being incorporated into the full accelerator. 9 refs., 4 figs