Search

Magnetized target fusion (MTF) is a means to compress plasmas to fusion conditions that uses magnetic fields to greatly reduce electron thermal conduction, thereby greatly reducing compression power density requirements. The compression is achieved by imploding the boundary, a metal shell. This effort pursues formation of the field-reversed configuration (FRC) type of magnetized plasma, and implosion of the metal shell by means of magnetic pressure from a high current flowing through the shell. We reported previously on experiments demonstrating that we can use magnetic pressure from high current capacitor discharges to implode long cylindrical metal shells (liners) with size, symmetry, implosion velocity, and overall performance suitable for compression of FRCs. We also presented considerations of using deformable liner-electrode contacts of Z-pinch geometry liners or theta pinch-driven liners, in order to have axial access to inject FRCs and to have axial diagnostic access. Since then, we have experimentally implemented the Z-pinch discharge driven deformable liner-electrode contact, obtained full axial coverage radiography of such a liner implosion, and obtained 2 112 dimensional MHD simulations for a variety of profiled thickness long cylindrical liners. The radiographic results indicate that at least 16 times radial compression of the inner surface of a 0.11-cm-thick AI liner was achieved, with a symmetric implosion, free of instability growth in the plane of the symmetry axis. We have also made progress in combining 21/2-D MHD simulations of FRC formation with imploding liner compression of FRCs. These indicate that capture of the injected FRC by the imploding liner can be achieved with suitable relative timing of the FRC formation and liner implosion discharges. Index Terms--Field-reversed configuration, liner implosion, magnetized plasma compression, magnetized target fusion.

Field reversed theta pinch technology is employed with programmed cusp fields at the theta coil ends to form high-density field-reversed configuration (FRC) plasmas. The well-formed FRC plasmas have volume-averaged density of 2 - 4 X [10.sup.22] [m.sup.-3], total temperature ([T.sub.e] + [T.sub.i]) of 300-500 eV, and plasma lifetime between 10-20 [micro]s in 50-70 mtorr of deuterium static gas fill. The achieved FRC parameters are very close to the desired target plasma requirements for magnetized target fusion. Index Terms--Field-reversed configuration, fusion reactors, magnetized target fusion, plasma confinement, plasma generation, plasma measurements, plasma pinch, plasmas.

We describe a program to demonstrate the scientific basis of magnetized target fusion (MTF). MTF is a potentially low-cost path to fusion which is intermediate in plasma regime between magnetic (MFE) and inertial fusion energy (IFE). MTF involves the compression of a magnetized target plasma and pressure times volume (PdV) heating to fusion relevant conditions inside a converging flux conserving boundary. We have chosen to demonstrate MTF by using a field-reversed configuration (FRC) as our magnetized target plasma and an imploding metal liner for compression. These choices take advantage of significant past scientific and technical accomplishments in MFE and defense programs research and should yield substantial plasma performance (n[tau] > [10.sup.13] s-[cm.sup.-3] T > 5 keV) using an available pulsed-power implosion facility at modest cost. We have recently shown the density, temperature, and lifetime of this FRC to be within a factor of 2-3 of that required for use as a suitable target plasma for MTF compression for a fusion demonstration. Index Terms--Field-reversed configuration, fusion energy, magnetized target fusion (MTF).

Solids subjected to high pressures, shocks, and/or deformation experience an increase in internal energy density and temperature due to adiabatic compression, shock heating, and plastic work heating, respectively. Analytic approximations are derived here for the internal energy and temperature changes that result from these processes based on the analytic constitutive model and Gruneisen equation of state of Steinberg. Although of general use, the utility of the expressions is demonstrated by the detailed example of a cylindrical metal tube filled with high explosives, and detonated on axis at one end. This geometry is often used to determine the detonation properties of high explosives, where it is known as the 'cylinder test.' The geometry is also of special interest for use as the armature of cylindrical magnetic flux compression pulsed current generators. The results are favorably compared with two dimension numerical simulations of the process using Lawrence Livermore National Laboratory's shock-hydro computer code CALE using the same model for the metal. Index Terms--Cylinder test, detonation, Hugoniot, plastic flow, plasticity, shock heating, shock wave.

S. Chandrasekhar, in his book, Hydrodynamic and Hydromagnetic Stability (New York: Dover, 1961), derives the stability criteria for a semi-infinite uniform density incompressible inviscid fluid with uniform horizontal velocity supported in a gravitational field by one of higher density and opposite velocity. A transitional layer of inviscid fluid with a density equal to the average of the upper and lower fluids, and a horizontal velocity that varies linearly with depth from that of the upper fluid at the top to that of the lower fluid at the bottom is assumed. This analysis of the Kevin-Helmholtz (K-H) instability may be transformed into a model of the effect of such a velocity sheared boundary layer on the Rayleigh-Taylor (R-T) instability of modes with wave numbers in the direction of the sheared velocity by reversing the sign of the top-bottom density differential. Orthogonal modes are unaffected by the shear in the linear limit and are, therefore, R-T unstable unless an independent mechanism for their stabilization is present, such as a magnetic field orthogonal to the sheared velocity. The combined R-T/K-H stability analysis is, therefore, expected to be most applicable for magnetically accelerated media such as a Z pinch with an axial velocity sheared outer layer orthogonal to the outer azimuthal magnetic field which drives the implosion. Index Terms--Hydrodynamic instability, Kevin-Helmholtz, Rayleigh-Taylor, sheared flow, Z pinch.

The design and first successful demonstration of an imploding solid liner with height to diameter ratio, radial convergence, and uniformity suitable for compressing a field reversed configuration is discussed. Radiographs indicated a very symmetric implosion with no instability growth, with ~13x radial compression of the inner liner surface prior to impacting a central measurement unit. The implosion kinetic energy was 1.5 megajoules, 34% of the capacitor stored energy of 4.4 megajoules. Index Terms--Capacitor bank, field reversed configuration, FRC, implosion, magnetized target fusion, megamp, MTF, radiography, solid liner.

Field reversed theta pinch technology is employed with programmed cusp fields at the theta coil ends to form high-density field-reversed configuration (FRC) plasmas. The well-formed FRC plasmas have volume-averaged density of 2 – 4 × 1022 m-3, total temperature (Te + Ti) of 300–500 eV, and plasma lifetime between 10–20 μs in 50–70 mtorr of deuterium static gas fill. The achieved FRC parameters are very close to the desired target plasma requirements for magnetized target fusion. [ABSTRACT FROM AUTHOR]