Wakefield generation in magnetized plasmas

We consider wakefield generation in plasmas by electromagnetic pulses propagating perpendicular to a strong magnetic field, in the regime where the electron cyclotron frequency is equal to or larger than the plasma frequency. PIC-simulations reveal that for moderate magnetic field strengths previous results are re-produced, and the wakefield wavenumber spectrum has a clear peak at the inverse skin depth. However, when the cyclotron frequency is significantly larger than the plasma frequency, the wakefield spectrum becomes broad-band, and simultaneously the loss rate of the driving pulse is much enhanced. A set of equations for the scalar and vector potentials reproducing these results are derived, using only the assumption of a weakly nonlinear interaction.Comment: 6 pages, 8 figure

The reflectivity of relativistic ultra-thin electron layers

The coherent reflectivity of a dense, relativistic, ultra-thin electron layer is derived analytically for an obliquely incident probe beam. Results are obtained by two-fold Lorentz transformation. For the analytical treatment, a plane uniform electron layer is considered. All electrons move with uniform velocity under an angle to the normal direction of the plane; such electron motion corresponds to laser acceleration by direct action of the laser fields, as it is described in a companion paper. Electron density is chosen high enough to ensure that many electrons reside in a volume \lambda_R^3, where \lambda_R is the wavelength of the reflected light in the rest frame of the layer. Under these conditions, the probe light is back-scattered coherently and is directed close to the layer normal rather than the direction of electron velocity. An important consequence is that the Doppler shift is governed by \gamma_x=(1-(V_x/c)^2)^{-1/2} derived from the electron velocity component V_x in normal direction rather than the full \gamma-factor of the layer electrons.Comment: 7 pages, 4 figures, submitted to the special issue "Fundamental Physics with Ultra-High Fields" in The European Physical Journal

Generation of ultra-short light pulses by a rapidly ionizing thin foil

A thin and dense plasma layer is created when a sufficiently strong laser pulse impinges on a solid target. The nonlinearity introduced by the time-dependent electron density leads to the generation of harmonics. The pulse duration of the harmonic radiation is related to the risetime of the electron density and thus can be affected by the shape of the incident pulse and its peak field strength. Results are presented from numerical particle-in-cell-simulations of an intense laser pulse interacting with a thin foil target. An analytical model which shows how the harmonics are created is introduced. The proposed scheme might be a promising way towards the generation of attosecond pulses. PACS number(s): 52.40.Nk, 52.50.Jm, 52.65.RrComment: Second Revised Version, 13 pages (REVTeX), 3 figures in ps-format, submitted for publication to Physical Review E, WWW: http://www.physik.tu-darmstadt.de/tqe

Relativistische Wechselwirkung intensiver kurzer Laserpulse mit ueberdichten Plasmen: Erzeugung hoher Harmonischer

The main subject of this thesis is a theoretical study of the generation of high harmonics by interaction of ultrashort laser pulses with condensed matter at intensities I#lambda#"2 = 10"1"7... 10"2"0Wcm"-"2#mu#m"2, where #lambda# is the laser wavelength. At these intensities, solid targets are rapidly ionized, and short pulses interact with sharp boundaries of overdense plasmas of electron densities on the order of the electron density in solids. The fact that electrons are driven to relativistic energies at intensities I#lambda#"2 >or#approx# 10"1"8Wcm"-"2#mu#m"2 is the most prominent feature of this new type of laser-plasma-interaction that can be approached by new short-pulse high-power lasers using the technique of Chirped-Pulse-Amplification. The basic numerical tool for studying the interaction of intense laser light with fully ionized collisionless plasma are kinetic simulations that reveal the selfconsistent, collective and relativistic evolution of plasma and fields. Here, a one-dimensional relativistic particle-in-cell (PIC) Code is used that has been developed within the framework of this thesis. This code allows for arbitrary polarization of incident and generated light, but restricts the emission of light to the specular direction. In order to interprete the simulation results, the interaction is also described analytically by hydrodynamic equations treating the plasma as a cold relativistic fluid. (orig.)SIGLEAvailable from TIB Hannover: RN 5339(219) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

LPIC++. A parallel one-dimensional relativistic electromagnetic particle-in-cell code for simulating laser-plasma-interaction

The code LPIC++ presented here, is based on a one-dimensional, electromagnetic, relativistic PIC code that has originally been developed by one of the authors during a PhD thesis at the Max-Planck-Institut fuer Quantenoptik for kinetic simulations of high harmonic generation from overdense plasma surfaces. The code uses essentially the algorithm of Birdsall and Langdon and Villasenor and Bunemann. It is written in C++ in order to be easily extendable and has been parallelized to be able to grow in power linearly with the size of accessable hardware, e.g. massively parallel machines like Cray T3E. The parallel LPIC++ version uses PVM for communication between processors. PVM is public domain software, can be downloaded from the world wide web. A particular strength of LPIC++ lies in its clear program and data structure, which uses chained lists for the organization of grid cells and enables dynamic adjustment of spatial domain sizes in a very convenient way, and therefore easy balancing of processor loads. Also particles belonging to one cell are linked in a chained list and are immediately accessable from this cell. In addition to this convenient type of data organization in a PIC code, the code shows excellent performance in both its single processor and parallel version. (orig.)Available from TIB Hannover: RN 5339(225) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman