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.

2012, Gopal, A., May, T., Herzer, S., Reinhard, A., Minardi, S., Schubert, M., Dillner, U., Pradarutti, B., Polz, J., Gaumnitz, T., Kaluza, M.C., Jäckel, O., Riehemann, S., Ziegler, W., Gemuend, H-P., Meyer, H-G., Paulus, G.G.

We report the first experimental observation of terahertz (THz) radiation from the rear surface of a solid target while interacting with an intense laser pulse. Experimental and two-dimensional particle-in-cell simulations show that the observed THz radiation is mostly emitted at large angles to the target normal. Numerical results point out that a large part of the emission originates from a micron-scale plasma sheath at the rear surface of the target, which is also responsible for the ion acceleration. This opens a perspective for the application of THz radiation detection for on-site diagnostics of particle acceleration in laser-produced plasmas.