Measurement of magnetic fields generated by a high-energy, high-intensity laser-driven millimeter-scale Helmholtz coil target is reported. The magnetic field is derived from a reverse current that passes through two coils of 1.25-mm radius. A peak field of 7T with a time decay of 17ns is inferred from a series of induction coil measurements when the hot-electron temperature driving the reverse current is approximately ∼15keV. A simple model of the laser-driven Helmholtz coil target suggests how the target should be optimized to produce high-peak fields and indicates that peak magnetic fields above 100T are accessible. This could lead to exciting experiments in laser-plasma physics, in particular, experiments related to laboratory astrophysics.

The VULCAN ͓C. N. Danson et al., Opt. Commun. 103, 392 ͑1993͔͒ laser at the UK Central Laser Facility is being used for laboratory-based simulations of collisionless shocks. By ensuring that key dimensionless parameters in the experiments have values similar to those of supernova remnants ͑SNRs͒, the hydrodynamics and magnetic field of the experiment are scaled to those of a SNR. This makes it possible to investigate experimentally the physics of collisionless magnetized shocks in such objects. The experiments are providing data against which to test current theory. Collisionless shock formation and the interaction of two counterpropagating colliding plasmas permeated by a strong magnetic field are discussed.

Results from an experimental study of the collisionless interaction of two laser-produced plasmas in a magnetic field with applications to supernova remnant shock physics are presented. The dynamics of the two plasmas and their interaction are studied with and without magnetic field through spatially and temporally resolved measurements of the electron density. Experimental results show that counter-propagating collisionless plasmas interpenetrate when no magnetic field is present. In contrast, results obtained with the addition of a 7.5 T magnetic field perpendicular to plasma flow show density features in the interaction area that only occur when the field is present. The reason for this remains uncertain. It is suggested that this results from an increase in the effective collisionality as the magnetic field reduces the ion and electron gyroradius below the size of the experiment.

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Results from a scaled, collision-free, laser-plasma experiment designed to address aspects of collisionless plasma interaction in a high-plasma β supernova remnant (SNR) are discussed. Ideal magneto-hydrodynamic scaling indicates that the experimental plasma matches the SNR plasma at 500 ps. Experimental data show that the magnetic field can alter the plasma density profile when two similar plasmas interact in a colliding geometry. These results are not explained by magnetic-field pressure; they do, however, suggest magnetic field penetration that localizes the plasma particles to the Larmor radius, which appears smaller than the size of the experiment and the particle mean-free paths and may thus increase the effective collisionality of the interacting plasma system.