We present measurements of a magnetic reconnection in a plasma created by two laser beams (1 ns pulse duration, 1 x 10(15) W cm(-2)) focused in close proximity on a planar solid target. Simultaneous optical probing and proton grid deflectometry reveal two high velocity, collimated outflowing jets and 0.7-1.3 MG magnetic fields at the focal spot edges. Thomson scattering measurements from the reconnection layer are consistent with high electron temperatures in this region.

Intense relativistic electron beams, produced by high-intensity short-pulse laser irradiation of a solid target, have many potential applications including fusion by fast ignition. Using a unique Fokker-Planck code, supported by analytic calculations, we show that fast electrons can be collimated into a beam even when the fast electron source is not strongly anisotropic, and we derive a condition for collimation to occur.

Abstract. Fast Ignition Inertial Confinement Fusion is a variant of inertial fusion in which DT fuel is first compressed to high density and then ignited by a relativistic electron beam generated by a fast (< 20 ps) ultra-intense laser pulse, which is usually brought in to the dense plasma via the inclusion of a re-entrant cone. The transport of this beam from the cone apex into the dense fuel is a critical part of this scheme, as it can strongly influence the overall energetics. Here we review progress in the theory and numerical simulation of fast electron transport in the context of Fast Ignition. Important aspects of the basic plasma physics, descriptions of the numerical methods used, a review of ignition-scale simulations, and a survey of schemes for controlling the propagation of fast electrons are included. Considerable progress has taken place in this area, but the development of a robust, high-gain FI 'point design' is still an ongoing challenge.

In solid targets irradiated by short pulse high intensity lasers, fast electrons have collision times longer than the laser pulse duration and mean free paths much larger than the radius of the laser spot. In these conditions, fast electron transport is dominated by electric and magnetic field. Although the fast electrons are collisionless, collisions of background electrons determine the ability of the background plasma to carry the return current which balances the fast electron current. Hence collisions are important even in this regime. A successful numerical simulation has to be able to model a plasma in which some electrons are collisionless and others are strongly collisional. An expansion of the electron distribution in spherical harmonics in momentum space is well suited to this, and we describe the formulation of the Vlasov-Fokker-Planck equation in terms of spherical harmonics and its solution in our KALOS code. We review the physics that must be modelled in a numerical simulation of fast electron transport and then describe KALOS.

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We study how the proton density in a target irradiated by an ultraintense laser affects the proton spectrum, with analytical models and Vlasov simulations. A low relative proton density gives rise to peaks in the energy spectrum. Furthermore, a target with the protons confined to a thin, low density layer produces a quasimonoenergetic spectrum. This is a simple technique for producing proton beams with a narrow energy spread for proton radiography of laser-plasma interactions.

Three models for nonlocal electron thermal transport are here compared against Vlasov-Fokker-Planck (VFP) codes to assess their accuracy in situations relevant to both inertial fusion hohlraums and tokamak scrape-off layers. The models tested are (i) a moment-based approach using an eigenvector integral closure (EIC) originally developed by Ji, Held, and Sovinec [Phys. Plasmas 16, 022312 (2009)]; (ii) the non-Fourier Landau-fluid (NFLF) model of Dimits, Joseph, and Umansky [Phys. Plasmas 21, 055907 (2014)]; and (iii) Schurtz, Nicolaï, and Busquet’s [Phys. Plasmas 7, 4238 (2000)] multigroup diffusion model (SNB). We find that while the EIC and NFLF models accurately predict the damping rate of a small-amplitude temperature perturbation (within 10% at moderate collisionalities), they overestimate the peak heat flow by as much as 35% and do not predict preheat in the more relevant case where there is a large temperature difference. The SNB model, however, agrees better with VFP results for the latter problem if care is taken with the definition of the mean free path. Additionally, we present for the first time a comparison of the SNB model against a VFP code for a hohlraum-relevant problem with inhomogeneous ionisation and show that the model overestimates the heat flow in the helium gas-fill by a factor of ∼2 despite predicting the peak heat flux to within 16%

We present a new magnetic field generation mechanism in underdense plasmas driven by the beating of two, co-propagating, Laguerre-Gaussian (LG) orbital angular momentum (OAM) laser pulses with different frequencies and also different twist indices. The resulting twisted ponderomotive force drives up an electron plasma wave with a helical rotating structure. To second order, there is a nonlinear rotating current leading to the onset of an intense, static axial magnetic field, which persists over a long time in the plasma (ps scale) after the laser pulses have passed by. The results are confirmed in three-dimensional particle-in-cell simulations and also theoretical analysis. For the case of 300 fs duration, 3.8×10 17 W/cm 2 peak laser intensity we observe magnetic field of up to 0.4 MG. This new method of magnetic field creation may find applications in charged beam collimation and microscale pinch.