Published: 12 September 2013, 09:20
Together with colleagues from the University of Düsseldorf and the Helmholtz Instiute Jena, the two ACP principal scientists Malte Kaluza and Christian Spielmann have just published an original research article on "Optical control of hard x-ray polarization by electron injection in a laser wakefield accelerator" (Nature Comm. 4, 2421, 2013).
Abstract: Laser-plasma particle accelerators could provide more compact sources of high-energy radiation than conventional accelerators. Moreover, because they deliver radiation in femtosecond pulses, they could improve the time resolution of X-ray absorption techniques. Here we show that we can measure and control the polarization of ultra-short, broad-band keV photon pulses emitted from a laser-plasma-based betatron source. The electron trajectories and hence the polarization of the emitted X-rays are experimentally controlled by the pulse-front tilt of the driving laser pulses. Particle-in-cell simulations show that an asymmetric plasma wave can be driven by a tilted pulse front and a non-symmetric intensity distribution of the focal spot. Both lead to a notable off-axis electron injection followed by collective electron-betatron oscillations. We expect that our method for an all-optical steering is not only useful for plasma-based X-ray sources but also has significance for future laser-based particle accelerators.