We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) in the vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approximately 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, and intensity fluctuations, are all consistent with the present models for SASE FELs.

Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL operation was performed. At saturation the FEL produces ultrashort pulses (30–100 fs FWHM) with a peak radiation power in the GW level and with full transverse coherence. The wavelength was tuned in the range of 95–105 nm.

Jefferson Laboratory's kW-level infrared free-electron laser utilizes a superconducting accelerator that recovers about $75\%$ of the electron-beam power. In achieving first lasing, the accelerator operated “straight ahead” to deliver 38-MeV, 1.1-mA cw current for lasing near $5\mu \mathrm{m}$. The waste beam was sent directly to a dump while producing stable operation at up to 311 W. Utilizing 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 $3.1\mu \mathrm{m}$.

A novel method of producing intense short wavelength radiation from relativistic electrons is described. The electrons are periodically bunched at the wavelength of interest enabling in-phase superradiant emission that is far more intense than from unbunched electrons. The periodic bunching is achieved in steps beginning with an array of beamlets emitted from a nanoengineered field emission array. The beamlets are then manipulated and converted to a longitudinal density modulation via a transverse-to-longitudinal emittance exchange. Periodic bunching at short wavelength is shown to be possible, and the partially coherent x-ray properties produced by inverse Compton scattering from an intense laser are estimated. The proposed method increases the efficiency of x-ray production by several orders of magnitude, potentially enabling compact x-ray sources to produce brilliance and flux similar to major synchrotron facilities.