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    X-ray spectroscopy of super-intense laser-produced plasmas for the study of nonlinear processes. Comparison with PIC simulations
    (Bristol : IOP Publ., 2017) Dalimier, E.; Ya Faenov, A.; Oks, E.; Angelo, P.; Pikuz, T.A.; Fukuda, Y.; Andreev, A.; Koga, J.; Sakaki, H.; Kotaki, H.; Pirozhkov, A.; Hayashi, Y.; Skobelev, I.Yu.; Pikuz, S.A.; Kawachi, T.; Kando, M.; Kondo, K.; Zhidkov, A.; Tubman, E.; Butler, N.M.H.; Dance, R.J.; Alkhimova, M.A.; Booth, N.; Green, J.; Gregory, C.; McKenna, P.; Woolsey, N.; Kodama, R.
    We present X-ray spectroscopic diagnostics in femto-second laser-driven experiments revealing nonlinear phenomena caused by the strong coupling of the laser radiation with the created plasma. Among those nonlinear phenomena, we found the signatures of the Two Plasmon Decay (TPD) instability in a laser-driven CO2 cluster-based plasma by analyzing the Langmuir dips in the profile of the O VIII Lyϵ line, caused by the Langmuir waves created at the high laser intensity 3 1018Wcm-2. With similar laser intensities, we reveal also the nonlinear phenomenon of the Second Harmonic Generation (SHG) of the laser frequency by analyzing the nonlinear phenomenon of satellites of Lyman δ and ϵ lines of Ar XVII. In the case of relativistic laser-plasma interaction we discovered the Parametric Decay Instability (PDI)-induced ion acoustic turbulence produced simultaneously with Langmuir waves via irradiation of thin Si foils by laser intensities of 1021Wcm-2.
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    Characterization of self-modulated electron bunches in an argon plasma
    (Bristol : IOP Publ., 2018) Gross, M.; Lishilin, O.; Loisch, G.; Boonpornprasert, P.; Chen, Y.; Engel, J.; Good, J.; Huck, H.; Isaev, I.; Krasilnikov, M.; Li, X.; Niemczyk, R.; Oppelt, A.; Qian, H.; Renier, Y.; Stephan, F.; Zhao, Q.; Brinkmann, R.; Martinez de la Ossa, A.; Osterhoff, J.; GrĂ¼ner, F.J.; Mehrling, T.; Schroeder, C.B.; Will, I.
    The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE (Advanced Wakefield Experiment) collaboration at CERN where this effect is used to generate proton bunches for the resonant excitation of high acceleration fields. Utilizing the availability of flexible electron beam shaping together with excellent diagnostics including an RF deflector, a supporting experiment was set up at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. After demonstrating the effect [1] the next goal is to investigate in detail the self-modulation of long (with respect to the plasma wavelength) electron beams. In this contribution we describe parameter studies on self-modulation of a long electron bunch in an argon plasma. The plasma was generated with a discharge cell with densities in the 1013 cm-3 to 1015 cm-3 range. The plasma density was deduced from the plasma wavelength as indicated by the self-modulation period. Parameter scans were conducted with variable plasma density and electron bunch focusing.