Abstract Details
Utilizing tilted laser-intensity fronts for electron-pointing control and off-axis injection in laser-wakefield acceleration
Author: Jens Osterhoff
Requested Type: Oral Only
Submitted: 2009-04-20 04:11:45
Co-authors: A.Popp, Zs.Major, M.Fuchs, R.Weingartner, R.Hörlein, J.Vieira, M.Marti, R.A.Fonseca, L.O.Silva, F.Grüner, D.Habs, F.Krausz, S.Karsch
Contact Info:
Max-Planck-Institute of Quantum Optics
Hans-Kopfermann-Str. 1
Garching, Bavaria 85748
Germany
Abstract Text:
Steady progress in the field of laser-wakefield acceleration of electrons in a plasma has identified this technique as a promising route towards the realization of an affordable and compact source of ultra-short and ultra-relativistic electron bursts. In order to reliably harness these electron beams for applications, such as the generation of XUV-undulator radiation or even the construction of a free-electron laser of table-top size, extensive control over key beam characteristics with sufficient shot-to-shot stability is crucial. Here, we discuss the possibility to finely tune one of these beam attributes, namely the pointing direction of laser-wakefield-accelerated electron bunches by controlling the tilt of the driving laser-pulse intensity front.
The according experiments have been carried out at the 25 TW ATLAS-laser facility at MPQ (Garching, Germany). By means of introducing defined amounts of laser-angular chirp, we were able to successfully alter the far-field evolution of the laser-pulse-front tilt (PFT), which resulted in a correlated achromatic change in the direction of electron pointing by ±10 mrad. This subtle effect was detectable owing to our low-fluctuation electron source delivering highly reproducible beams with good pointing stability (~1.7 mrad RMS) and sub-mrad divergence, which allowed for a meaningful statistical evaluation.
These experimental results are supported by full-featured simulations performed with the 3D-PIC code OSIRIS, which suggest that the steering effect is caused by a temporally evolving axially asymmetric wakefield profile induced by the tilted laser front. This asymmetry leads to a tilted electron-density profile forcing the driver laser to deviate from its original path and consequently initiates a directional change of the excited plasma wake and the captured relativistic particles.
In addition, these simulations indicate the feasibility of an off-axis injection of electrons into a wake bucket by PFT, which may potentially be used to induce defined collective betatron oscillations of the captured electron stem. Preliminary experimental evidence of this effect will also be presented.
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