Charles W. Hartman

Investigations of the magnetic structure and the decay of a plasma‐gun‐generated compact torus

The results of a series of experimental measurements of compact toroidal (CT) plasmas produced by a magnetized coaxial plasma gun injecting into a flux‐conserving metallic liner are reported. The experiments were performed on the Beta II facility at Lawrence Livermore National Laboratory. The magnetic equilibria are well described by a force‐free eigenmode structure that results from an extension of Taylor’s theory of the reversed‐field pinch. Consideration of helicity conservation during relaxation of the composite plasma‐gun flux‐conserver system to the final state equilibrium yields theoretical expressions that are compared with the experiment. In particular the CT poloidal flux (ψpol) and the overall electrical efficiency for producing the CT are predicted to be functions of the plasma gun inner‐electrode flux (ψgun) and the volt‐seconds input to the gun discharge (∫∞0 V dt). Away from a cutoff at too low values of ∫∞0  V dt or too high values, ψgun ,ψpol scales linearly with the square root of the pr...

Experimental demonstration of compact torus compression and acceleration

Tests of compact torus (CT) compression on the RACE device [Phys. Rev. Lett. 61, 2843 (1988)] have successfully demonstrated stable compression by a factor of 2 in radius, field amplification by factors of 2–3 to 20 kG, and compressed densities exceeding 1016 cm−3. The results are in good agreement with two‐dimensional magnetohydrodynamic simulations of the CT dynamics. The CT is formed between a pair of coaxial conical conductors that serve as both a flux conserver for stable, symmetric formation and as electrodes for the compression and acceleration phases. The CT is compressed by J×B forces (poloidal current, toroidal field) when a 120 kV, 260 kJ capacitor bank is discharged across the electrodes. The CT reaches two‐fold compression to a radius of 8 cm and a length of 20–30 cm near the time of peak current, 10 μsec (many Alfven times) after the accelerator fire time, and is subsequently accelerated in a 150 cm straight coaxial section to velocities in the range 1.5–6.5×107 cm/sec. A new set of accelera...

Production of field‐reversed plasma with a magnetized coaxial plasma gun

Experimental data are presented on the production of field‐reversed deuterium plasma by a modified coaxial plasma gun. The coaxial gun is constructed with solenoid coils along the inner and outer electrodes that, together with an external guide field solenoid, form a magnetic cusp at the gun muzzle. The net flux inside the inner electrode is arranged to be opposite the external guide field and is the source of field‐reversed flux trapped by the plasma. The electrode length is 145 cm, the diameter of the inner (outer) electrode is 15 cm (32 cm). The gun discharge is driven with a 232‐μF 40‐kV capacitor bank. Acceleration of plasma through the magnetic cusp at the gun muzzle results in entrainment of field‐reversed flux that is detected by magnetic probes 75 cm from the gun muzzle. Field‐reversed plasma has been produced for a variety of experimental conditions. In one typical case, the guide magnetic field was B0=4.8 kG and the change in axial magnetic field ΔBz normalized to B0 was ΔBz /B0=−3.1. Total fie...

Hot‐Electron Plasma Confinement in Magnetic Fields with Compensating Curvature

Loss of plasma across B is observed when the average field curvature is destabilizing in the hydromagnetic sense. Under stable curvature conditions loss across B is suppressed and enhanced end‐loss bursts appear.

The flow-through Z-pinch for fusion energy production

The authors discuss a high-density fusion reactor which utilizes a flow-through Z pinch magnetic confinement configuration. Assessment of this reactor system is motivated by simplicity and small unit size (few hundred MWe) and immunity to plasma contamination made possible at high density. The type reactor discussed here would employ a liquid Li vortex as the first wall/blanket to capture fusion neutrons with minimum induced radioactivity and to achieve high wall loading and a power density of 200 W/cm{sup 3}.

Diagnostic measurements of currents and magnetic fields in axisymmetric plasmas

The azimuthal current and magnetic flux in an axisymmetric torus or mirror are related to the (anisotropic) plasma pressure. Measurements by a Rogowski loop and a flux loop can be used to determine the spatially averaged components of pressure along and across the magnetic field.