LMU, München
LBNL, Berkeley, California
Recent breakthroughs in the field of laser-plasma electron accelerators have led to intrinsically ultrashort (supposedly ~5 fs rms) electron beams with energies on the GeV-scale. In these accelerators, a high-power laser beam is focussed into a gas target and excites a plasma wave, whose fields can accelerate electrons to ultrarelativistic energies over distances of only a few centimeters. Owing to their unprecedented features, these electron beams are suited for driving a next generation of ultrashort X-ray light sources. Both, spontaneous undulator light sources with femtosecond to attosecond pulse duration and, later, FEL-emission could be realized on a laboratory-sized scale. In this talk, we will present first experimental breakthroughs towards this end, manifesting itself in a laser-driven soft x-ray undulator source. We will also discuss a design for a first table-top FEL demonstration experiment.
USTRAT/SUPA, Glasgow
Instituto Superior Tecnico, Lisbon
University of Oxford, Oxford
GoLP, Lisbon
STFC/RAL, Chilton, Didcot, Oxon
University of Dundee, Nethergate, Dundee, Scotland
OXFORDphysics, Oxford, Oxon
University of Oxford, Clarendon Laboratory, Oxford
UAD, Dundee
University of Glasgow, Glasgow
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
We describe the latest results to develop brilliant incoherent and coherent radiation sources based on laser-plasma wakefield accelerators. We demonstrate both experimentally and theoretically a brilliant gamma ray sub 10 femtosecond source based on betatron radiation in the plasma density wake trailing behind an intense laser pulse. Furthermore, experimental and theoretical progress towards a compact free-electron laser based on a laser-plasma wakefield accelerator will be discussed.
LOA, Palaiseau
GoLP, Lisbon
PSI, Villigen
Free-electron lasers have been recently evolving very fast in the extreme-ultraviolet to soft X-ray region. Once seeded with high harmonics, these schemes are considered as next generation soft X-ray light sources delivering ultrashort pulses with high temporal and spatial coherence. Here we present a detailed experimental study of a kHz two-colour (fundamental + second harmonic) high harmonic generation and investigate its potential as a suitable evolution of the actual seeding sources. It turns out that this source (both odd and even harmonics) is highly tuneable, and delivers intense radiations with only one order of magnitude difference in the photon yield from 65 nm to 13 nm. We also observed an astonishing aberration-free character of these harmonics (aberration below λ/17 rms at 44 nm). Finally, the variable linear polarization of the harmonics was revealed to be easily controllable with the generation conditions. Then, the implementation of this technique on seeded FELs would allow amplifications, with perfect beam quality, to be achieved at wavelengths shorter than previously accessible.
PSI, Villigen
Recently, several groups suggested a new FEL operation mode with low single bunch charge to generate sub-fs long longitudinal coherent XFEL photon pulses, so called single spike lasing mode. At PSI, we studied this mode to generate single spike XFEL photon beams at 1 nm and 0.1 nm. We report several critical issues which we found with such an operation mode, namely, ultra-tight RF jitter tolerances, alignment tolerances, and challenging beam diagnostic specifications for the stable single spike lasing mode.
BNL, Upton, Long Island, New York
Short noise in electron beam distribution is the main source of noise in high-gain FEL amplifiers ranging single- and multi-stage HGHG FEL to FEL amplifier for Coherent Electron Cooler. This noise also imposes a fundamental limit on FEL gain to about six orders of magnitude, after which SASE FEL does saturate. There is a number of advantages can be gain if short noise in the electron beam and corresponding spontaneous radiation are strongly suppressed. A traditional passive method used in low-energy microwave electronic devices* has a number of significant limitations and hardly can be used for highly inhomogeneous beams used in modern high gain FELs. In this paper we present a novel active method of suppressing the short noise in relativistic electron beams by many orders of magnitude. We present theoretical description of the process, the fundamental limitation of the process. We also discuss potential experiment demonstrating the proposed technique.
* I.e. waiting for plasma oscillation to transfer short noise in the density distribution into the velocity noise. This technique is very successful for low-energy DC beams with constant peak current.