Commissioning of a multi-beamline femtoslicing facility at SOLEIL

Multiplexed emitting system for an energy-recovery-linac-based coherent light source

Recently, a novel approach has been proposed to produce ultrashort, fully coherent high-repetition-rate EUV and X-ray radiation by combining an energy recovery linac (ERL) with the angular-dispersion-induced microbunching methodology. It is critical to maintain microbunching when the beam passes through bending magnets between the undulators, which results in difficulties supporting multiple beamlines. In this paper, the design of a multiplexed emitting system consisting of multi-bend achromats, matching sections and radiators to facilitate the multi-beamline operation is presented. Theoretical analysis and numerical simulations have been carried out and the results show that the microbunching and beam quality can be well maintained after four times of bending. Five radiation pulses with a central wavelength of 13.5 nm and peak power at the MW level have been produced by the same electron beam via this multiplexed emitting system. The proposed method holds potential in the multi-beamline operation of ERL- or storage-ring-based coherent light sources.

Piezo-modulated active grating for selecting X-ray pulses separated by one nanosecond

We present a novel method of temporal modulation of X-ray radiation for time resolved experiments. To control the intensity of the X-ray beam, the Bragg reflection of a piezoelectric crystal is modified using comb-shaped electrodes deposited on the crystal surface. Voltage applied to the electrodes induces a periodic deformation of the crystal that acts as a diffraction grating, splitting the original Bragg reflection into several satellites. A pulse of X-rays can be created by rapidly switching the voltage on and off. In our prototype device the duty cycle was limited to ∼1 ns by the driving electronics. The prototype can be used to generate X-ray pulses from a continuous source. It can also be electrically correlated to a synchrotron light source and be activated to transmit only selected synchrotron pulses. Since the device operates in a non-resonant mode, different activation patterns and pulse durations can be achieved.

Laser-slicing at a low-emittance storage ring

Laser-slicing at a diffraction-limited storage ring light source in the soft X-ray region is investigated with theoretical and numerical modelling. It turns out that the slicing efficiency is favoured by the ultra-low beam emittance, and that slicing can be implemented without interference to the standard multi-bunch operation. Spatial and spectral separation of the sub-picosecond radiation pulse from a hundreds of picosecond-long background is achieved by virtue of 1:1 imaging of the radiation source. The spectral separation is enhanced when the radiator is a transverse gradient undulator. The proposed configuration applied to the Elettra 2.0 six-bend achromatic lattice envisages total slicing efficiency as high as 10^-7, one order of magnitude larger than the demonstrated state-of-the-art, at the expense of pulse durations as long as 0.4 ps FWHM and average laser power as high as ∼40 W.

Recent advances in ultrafast X-ray sources

Over more than a century, X-rays have transformed our understanding of the fundamental structure of matter and have been an indispensable tool for chemistry, physics, biology, materials science and related fields. Recent advances in ultrafast X-ray sources operating in the femtosecond to attosecond regimes have opened an important new frontier in X-ray science. These advances now enable: (i) sensitive probing of structural dynamics in matter on the fundamental timescales of atomic motion, (ii) element-specific probing of electronic structure and charge dynamics on fundamental timescales of electronic motion, and (iii) powerful new approaches for unravelling the coupling between electronic and atomic structural dynamics that underpin the properties and function of matter. Most notable is the recent realization of X-ray free-electron lasers (XFELs) with numerous new XFEL facilities in operation or under development worldwide. Advances in XFELs are complemented by advances in synchrotron-based and table-top laser-plasma X-ray sources now operating in the femtosecond regime, and laser-based high-order harmonic XUV sources operating in the attosecond regime. This article is part of the theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays'.

Coherent THz Emission Enhanced by Coherent Synchrotron Radiation Wakefield

We demonstrate that emission of coherent transition radiation by a ∼1 GeV energy-electron beam passing through an Al foil is enhanced in intensity and extended in frequency spectral range, by the energy correlation established along the beam by coherent synchrotron radiation wakefield, in the presence of a proper electron optics in the beam delivery system. Analytical and numerical models, based on experimental electron beam parameters collected at the FERMI free electron laser (FEL), predict transition radiation with two intensity peaks at ∼0.3 THz and ∼1.5 THz, and extending up to 8.5 THz with intensity above 20 dB w.r.t. the main peak. Up to 80-µJ pulse energy integrated over the full bandwidth is expected at the source, and in agreement with experimental pulse energy measurements. By virtue of its implementation in an FEL beam dump line, this work promises dissemination of user-oriented multi-THz beamlines parasitic and self-synchronized to EUV and x-ray FELs.