2013, Steinke, S., Hilz, P., Schnürer, M., Priebe, G., Bränzel, J., Abicht, F., Kiefer, D., Kreuzer, C., Ostermayr, T., Schreiber, J., Andreev, A.A., Yu, T.P., Pukhov, A., Sandner, W.

We present experimental results on ion acceleration with circularly polarized, ultrahigh contrast laser pulses focused to peak intensities of 5×1019 W cm-2 onto polymer targets of a few 10 nanometer thickness. We observed spatially and energetically separated protons and carbon ions that accumulate to pronounced peaks around 2 MeV containing as much as 6.5% of the laser energy. Based on particle-in-cell simulation, we illustrate that an early separation of heavier carbon ions and lighter protons creates a stable interface that is maintained beyond the end of the radiation pressure dominated acceleration process.

2010, Pfotenhauer, S.M., Jäckel, O., Polz, J., Steinke, S., Schlenvoigt, H.-P., Heymann, J., Robinson, A.P.L., Kaluza, M.C.

We present a novel, cascaded acceleration scheme for the generation of spectrally controlled ion beams using a laser-based accelerator in a 'double-stage' setup. An MeV proton beam produced during a relativistic laser-plasma interaction on a thin foil target is spectrally shaped by a secondary laser-plasma interaction on a separate foil, reliably creating well-separated quasi-monoenergetic features in the energy spectrum. The observed modulations are fully explained by a one-dimensional (1D) model supported by numerical simulations. These findings demonstrate that laser acceleration can, in principle, be applied in an additive manner. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

2010, Sokollik, T., Paasch-Colberg, T., Gorling, K., Eichmann, U., Schnürer, M., Steinke, S., Nickles, P.V., Andreev, A., Sandner, W.

We report on our experiments on laser-driven ion acceleration using fully isolated mass-limited spheres with a diameter down to 8μm for the first time. Two-dimensional (2D) particle-in-cell (PIC) and hydro-code simulations were used to show that the pre-plasma at both the front and rear sides of the target strongly affect the efficiency of the ion acceleration. The mechanism of the plasma flow around mass-limited targets has not yet been identified for laser-driven ion acceleration. Our models indicate that this effect is the cause of the observed limitation to the ion-beam energy in both previous experiments and in our own. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.