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- ItemA cascaded laser acceleration scheme for the generation of spectrally controlled proton beams(College Park, MD : Institute of Physics Publishing, 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.
- ItemObservation of energetic terahertz pulses from relativistic solid density plasmas(Bristol : IOP, 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.