Sustained kilowatt lasing in a free-electron laser with same-cell energy recovery

Jefferson Laboratory's kW-level infrared free-electron laser utilizes a sup erconducting accelerator that recovers about 75% of the electron-beam power . In achieving first lasing, the accelerator operated "straight ahead" to d eliver 38-MeV, 1.1-mA cw current for lasing near 5 mu m, The waste beam was sent directly to a dump while producing stable operation at up to 311 W. U tilizing the recirculation loop to send the electron beam back to the linac for energy recovery, the machine has now recovered cw average currents up to 5 mA, and has lased cw with up to 1720 W output at 3.1 mu m.