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Title: Semianalytical study of the propagation of an ultrastrong femtosecond laser pulse in a plasma with ultrarelativistic electron jitter

The interaction of a multi-petawatt, pancake-shaped laser pulse with an unmagnetized plasma is studied analytically and numerically in a regime with ultrarelativistic electron jitter velocities, in which the plasma electrons are almost completely expelled from the pulse region. The study is applied to a laser wakefield acceleration scheme with specifications that may be available in the next generation of Ti:Sa lasers and with the use of recently developed pulse compression techniques. A set of novel nonlinear equations is derived using a three-timescale description, with an intermediate timescale associated with the nonlinear phase of the electromagnetic wave and with the spatial bending of its wave front. They describe, on an equal footing, both the strong and the moderate laser intensity regimes, pertinent to the core and to the edges of the pulse. These have fundamentally different dispersive properties since in the core the electrons are almost completely expelled by a very strong ponderomotive force, and the electromagnetic wave packet is imbedded in a vacuum channel, thus having (almost) linear properties. Conversely, at the pulse edges, the laser amplitude is smaller, and the wave is weakly nonlinear and dispersive. New nonlinear terms in the wave equation, introduced by the nonlinear phase, describemore » without the violation of imposed scaling laws a smooth transition to a nondispersive electromagnetic wave at very large intensities and a simultaneous saturation of the (initially cubic) nonlocal nonlinearity. The temporal evolution of the laser pulse is studied both analytically and by numerically solving the model equations in a two-dimensional geometry, with the spot diameter presently used in some laser acceleration experiments. The most stable initial pulse length is estimated to exceed ≳1.5–2 μm. Moderate stretching of the pulse in the direction of propagation is observed, followed by the development of a vacuum channel and of a very large electrostatic wake potential, as well as by the bending of the laser wave front.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Zemun (Serbia)
  2. Dipartimento di Fisica, Università di Napoli “Federico II,” M.S. Angelo, Napoli (Italy)
  3. (Italy)
  4. Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar)
  5. SPIN-CNR, Complesso Universitario di M.S. Angelo, Napoli (Italy)
Publication Date:
OSTI Identifier:
22408347
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 4; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATION; AMPLITUDES; ELECTROMAGNETIC RADIATION; ELECTRONS; LASERS; NONLINEAR PROBLEMS; PETAWATT POWER RANGE; PLASMA; PONDEROMOTIVE FORCE; PULSES; RELATIVISTIC RANGE; SCALING LAWS; TIME DEPENDENCE; TWO-DIMENSIONAL SYSTEMS; VELOCITY; WAVE EQUATIONS