Reduction of energy sweep of the ETA-II beam

The ETA-II 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 +or-1% of the wiggler resonance value. In initial operations the ETA-II 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 accelerator induction cells. A new multicable pulsed power feed design was tested in a shortened version of ETA-II 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.<>