Design considerations for table-top, laser-based VUV and X-ray free electron lasers

Abstract

A recent breakthrough in laser-plasma accelerators, based upon ultrashort high-intensity lasers, demonstrated the generation of quasi-monoenergetic GeV-electrons. With future Petawatt lasers ultra-high beam currents of ∼ 100 kA in ∼ 10 fs can be expected, allowing for drastic reduction in the undulator length of free-electron-lasers (FELs). We present a discussion of the key aspects of a table-top FEL design, including energy loss and chirps induced by space-charge and wakefields. These effects become important for an optimized table-top FEL operation. A first proof-of-principle VUV case is considered as well as a table-top X-ray-FEL which may open a brilliant light source also for new ways in clinical diagnostics.

Generalized algorithm for control of numerical dispersion in explicit time-domain electromagnetic simulations

“…Since then, efforts have focused on obtaining beams useful for highenergy particle colliders [9] and radiation sources [16][17][18][19]. This involves developing longer acceleration stages to achieve greater total energy gain, and controlling the injection process for higher beam quality.…”

Miniature magnetic devices for laser-based, table-top free-electron lasers

“…Appealing features of laser-plasma accelerators are the mm-scale size that is required for the generation of GeV electron energies [4] and the high peak currents of up to 100 kA combined with short bunch lengths on the 10 fs scale [6]. Especially the latter suggests the application of laser-accelerated electron bunches as drivers for secondary light sources, either via incoherent synchrotron radiation [7], undulator radiation, or coherent FEL (free-electron laser) radiation [8].…”

“…In a recent design study [8], our group pointed out the feasibility of the operation of a laser-plasma accelerator driven table-top FEL. Thus, the principle aim of this paper is to give experimental evidence that the crucial components that have to be used to control the propagation of the electron beam can be sufficiently miniaturized.…”

“…The radiation bandwidth, and correspondingly the electron energy spread, has to be smaller ( 1 = 1 2 = < 2 ) than the so-called Pierce parameter [10]. In large-scale FELs this parameter is typically of the order of 10 ÿ4 -10 ÿ3 while for laser-based FELs it can be 1 order of magnitude larger, especially due to the high peak currents [8]. Tolerances of the magnetic field distribution of the undulator are accordingly determined by the Pierce parameter, as will be discussed quantitatively later.…”

“…Besides the most demanding scenario of the table-top FEL [8] for which the components presented here have been developed, miniaturized lenses and undulators will have numerous applications in conventional as well as laser-driven accelerators. High gradient and thus short focal-length magnetic lenses have the potential for generating focal spots in the sub-micron range.…”