We propose the use of a ultra-relativistic electron beam interacting with a few-cycle, intense laser pulse and an intense pulse of the coherent x-rays to produce a multi-MW intensity, x-ray pulses
approximately 100 attoseconds in duration. Due to a naturally-occurring frequency chirp, these pulses can be further temporally compressed.
We describe the design concepts for a potential future source of femtosecond x-ray pulses based on synchrotron radiation production in a recirculating electron linac. Using harmonic cascade free-electron lasers (FEL's) and spontaneous emission in short-period, narrow-gap insertion devices, a broad range of photon energies are available with tunability from EUV to hard x-ray regimes. Photon pulse durations are controllable and range from 10 fs to 200 fs, with fluxes 107-1012 photons per pulse. Full spatial and temporal coherence is obtained for EUV and soft X-rays. A fiber laser master oscillator and stabilized timing distribution scheme are proposed to synchronize accelerator rf systems and multiple lasers throughout the facility, allowing timing synchronization between sample excitation and X-ray probe of approximately 20-50 fs.
The Linac-based Ultrafast X-ray source (LUX) is a proposed recirculating linear accelerator for the purpose of producing intense, tunable, high repetition rate ultrafast x-ray pulses. An angle-time or position-time correlation is induced in the electron bunches by a dipole-mode RF cavity. Undulators and wigglers are sources of synchrotron radiation. Asymmetrically-cut crystals are used as optical elements of an x-ray pulse compression scheme. X-ray pulse durations of 50-100 fs are obtained over a range of photon energies from 2 to 12 keV. An undulator beamline consists of a collimating mirror, two asymmetric crystals and Kirkpatrick-Baez mirrors and provides compressed, monochromatic and focused x-rays for time-resolved experiments.
We are reporting on the current design status of the 200 kW average power FEL at a 0.84 micron wavelength for power beaming of satellites. The project includes a cw RF photocathode gun injector, a cw linear accelerator, achromatic beam transport lines and an FEL amplifier. Problems that are specific to our design are considered.
The FELs based on the rf accelerator-recuperator and the electron outcoupling is promising for obtaining average output power of hundreds of kilowatts. We present basic considerations for the system stability and performance optimization for this scheme.