The temporal structure of the storage-ring free-electron laser at Elettra shows high sensitivity to electron-beam instabilities. In fact, even small beam perturbations may affect the FEL dynamics and periodically switch off the laser. In order to improve the FEL operation and performance, different and complementary feedback systems have been activated. This paper reports on their beneficial ef...

A low-energy undulator test line (LEUTL) is under construction at the Advanced Photon Source (APS). This line will initially be used to demonstrate a free-electron laser (FEL) based on the self-amplified spontaneous-emission (SASE) process. The FEL simulation programs, TDA3D and GENESIS, together with several other codes have been used for the LEUTL project. In order to increase the confidence ...

We report the first experimental demonstration of a slippagedominant superradiant free-electron laser (FEL) using an ultrafast seed-laser pulse. We measured the evolution of the longitudinal phase space in the slippage-dominant superradiant regime. With a roughly 1% variation in the electron beam energy, we observed a seed-like fully longitudinal coherence, and a 2% wavelength shift from the se...

BACKGROUND AND OBJECTIVES In theory, infrared vibrational bands could be used for selective photothermolysis of lipid-rich tissues such as fat, sebaceous glands, or atherosclerotic plaques. STUDY DESIGN/MATERIALS AND METHODS Absorption spectra of human fat were measured, identifying promising bands near 1,210 and 1,720 nm. Photothermal excitation of porcine fat and dermis were measured with a...

We report results from characterization of the output of a high-gain harmonic-generation (HGHG) free-electron laser (FEL). A CO2 seed laser at a wavelength of 10.6 μm is amplified and frequencydoubled in the FEL to produce 5.3-μm output. The wavelength spectrum, pulse duration, and correlation length of the output verify that the light is longitudinally coherent. Comparisons of the measured ele...

We demonstrate how a steady-state train of ultrashort radiation pulses can be produced utilizing a new free-electron laser ~FEL! configuration, the injection-locked regenerative klystron amplifier ~IRKA!. This configuration consists of two elements: ~1! a prebuncher, which microbunches the electron beams at the desired output wavelength, and ~2! a multipass FEL operated at a very small cavity d...

The LCLS Free-Electron Lasers operates in the wavelength range of 1.5 15 Angstrom, using an electron beam with an energy between 4.5 and 14.5 GeV. The generation of the electron beam, the preservation of its brightness during acceleration and compression, and the amplification of the spontaneous radiation within the FEL can only be described by a consistent set of simulation codes. We present t...

Recently a scheme entitled echo-enabled harmonic generation (EEHG) was proposed for producing short wavelength FEL radiation that allows far higher harmonic numbers to be accessed as compared with the normal limit arising from incoherent energy spread. In this paper we study the feasibility of a single EEHG stage to generate coherent radiation in the ”water window” (24 nm wavelength) directly f...

We have investigated dissociative ionization of N2 and O2 molecules by 52 nm extreme-ultraviolet light pulses at the free-electron laser facility in Japan. Distributions of kinetic energy release were measured at two different laser power densities below 3 × 1013 W cm−2 and intermediate and final states of the sequential two photon transitions were identified. A free-electron laser (FEL) based ...