Performance of the accelerator driver of Jefferson Laboratory's free-electron laser
Bohn CL., Benson S., Biallas G., Campisi I., Douglas D., Evans R., Fugitt J., Hill R., Jordan K., Krafft G., Li R., Merminga L., Neil G., Piot P., Preble J.
The driver for Jefferson Lab's kW-level infrared free electron laser (FEL) is a superconducting, recirculating accelerator that recovers about 75% of the electron-beam power and converts it to radiofrequency power. In achieving first lasing, the accelerator operated `straight-ahead' to deliver 38 MeV, 1.1 mA cw current through the wiggler for lasing at wavelengths in the vicinity of 5 μm. Just prior to first lasing, measured rms beam properties at the wiggler were 7.5±1.5 mm-mr normalized transverse emittance, 26±7 keV-deg longitudinal emittance, and 0.4±0.1 ps bunch length which yielded a peak current of 60±15 A. The waste beam was then sent directly to a dump, bypassing the recirculation loop. Stable operation at up to 311 W cw was achieved in this mode. Commissioning the recirculation loop then proceeded. As of this Conference, the machine has recirculated cw average current up to 4 mA, and has laced cw with energy recovery up to 710 W.