[en] A cryogenic extrusion system has succeeded in extruding into vacuum four 0.6 mm diameter solid D₂ fibers at a temperature of 13 K to form a square array 2.0 cm on the side. The system is designed to allow a wide variety of extrusion geometries by virtue of a replaceable distribution manifold/die assembly. A unique cryogenic high vacuum valve which precedes the manifold is necessary to preserve the vacuum thermal insulation of the cryostat during the condensation and solidification process, but allow the resultant solid to flow through the manifold to the die under piston pressure. Flexibility in the choice of gas species used is made possible by isothermal temperature controlled operation down to 10 K. The principle application envisioned is the rapid in situ formation of a circular array of many fibers for use as a z pinch load. Other potential applications and pertinent design and operational details are discussed

[en] The authors have used 12 megamp, 5 megajoule axial discharges to electromagnetically implode tapered thickness spherical aluminum shells, achieving peak implosion velocities above 20 km/sec inner surface, 10 km/sec thickness averaged. The shell thickness was proportional to the inverse of the square of the cylindrical radius. This causes the ratio of magnetic pressure to shell areal mass density (and spherical acceleration) to be independent of polar angle, so that the spherical shape is nominally maintained during the implosion. The authors have used these implosions to compress hot hydrogen plasmas with initial pressure about 100 atm and initial temperature above 1 eV. The hot hydrogen plasmas were injected beforehand using 1 megamp, 100 kilojoule range co-axial gun discharges through a circular array of vanes to strip away magnetic field. The imploding shell and the compressed hot hydrogen working fluid's effect on a diagnostic compression target were observed with radiography. Interior magnetic probes and auxiliary shots without working fluid injection were used to confirm that there is no magnetic field interior to the imploding aluminum shell. Thus, diagnostic target compression, which was observed in working fluid compression experiments, was presumably due to the compressed hot hydrogen pressure

[en] The authors have used 12 megamp, 5 megajoule axial discharges to electromagnetically implode aluminum shells in tapered spherical and cylindrical geometry, achieving peak implosion velocities above 20 km/sec inner surface, 10 km/sec thickness averaged. They have used these implosions to compress pre-inserted hot hydrogen plasma working fluid with initial pressure above 100 atm and initial temperature above 1 eV. The hot hydrogen plasmas are pre-inserted using 1 megamp, 100 kilojoule range co-axial gun discharges, injected through a circular array of vanes to strip away magnetic field. The working fluid injection was observed with auxiliary experiments, using diagnostically accessible injection chambers similar to the solid liner interior volume. Differences in instability growth, evident on the outer surface of the imploding shell with radiography, were observed for spherical and cylindrical shells, and for implosions with and without working fluid. Comparison of experimental and theoretical results, and interpretation of experimental results will be discussed

[en] We have magnetically driven a tapered-thickness spherical aluminum shell implosion with a 12.5 MA axial discharge. The initially 4 cm radius, 0.1 to 0.2 cm thick, ±45^degree latitude shell was imploded along conical electrodes. The implosion time was approximately 15 μsec. Radiography indicated substantial agreement with 2D-MHD calculations. Such calculations for this experiment predict final inner-surface implosion velocity of 2.5 to 3 cm/μsec, peak pressure of 56 Mbar, and peak density of 16.8 g/cm³ (>6 times solid density). The principal experimental result is a demonstration of the feasibility of electromagnetic-driven spherical liner implosions in the cm/μsec regime

[en] Magneto-inertial fusion (MIF) approaches take advantage of an embedded magnetic field to improve plasma energy confinement by reducing thermal conduction relative to conventional inertial confinement fusion (ICF). MIF reduces required precision in the implosion and the convergence ratio. Since 2008 (Wurden et al 2008 IAEA 2008 Fusion Energy Conf. (Geneva, Switzerland, 13–18 October) IC/P4-13 LA-UR-08-0796) and since our prior refereed publication on this topic (Degnan et al 2008 IEEE Trans. Plasma Sci. 36 80), AFRL and LANL have developed further one version of MIF. We have (1) reliably formed, translated, and captured field reversed configurations (FRCs) in magnetic mirrors inside metal shells or liners in preparation for subsequent compression by liner implosion; (2) imploded a liner with interior magnetic mirror field, obtaining evidence for compression of a 1.36 T field to 540 T; (3) performed a full system experiment of FRC formation, translation, capture, and imploding liner compression operation; (4) identified by comparison of 2D-MHD simulation and experiments factors limiting the closed-field lifetime of FRCs to about half that required for good liner compression of FRCs to multi-keV, 10¹⁹ ion cm⁻³, high energy density plasma (HEDP) conditions; and (5) designed and prepared hardware to increase that closed-field FRC lifetime to the required amount. Those lifetime experiments are now underway, with the goal of at least doubling closed-field FRC lifetimes and performing FRC implosions to HEDP conditions this year. These experiments have obtained imaging evidence of FRC rotation, and of initial rotation control measures slowing and stopping such rotation. Important improvements in fidelity of simulation to experiment have been achieved, enabling improved guidance and understanding of experiment design and performance. (paper)

[en] To demonstrate the physics basis for Magnetized Target Fusion (MTF), we have designed a field reversed configuration (FRC) target plasma to ultimately be compressed within an imploding metal flux conserver (liner). This new, high energy density FRC device, named FRX-L, is operating at Los Alamos as a compact 'theta-pinch' formation FRC. The system capability includes a 0.5 T bias field, 70 kV 250 kHz ringing pre-ionization, and a 1.5 MA, 200 kJ main-theta-coil bank. We show FRC data with plasma parameters approaching the desired MTF requirements, examples of substantial Ohmic heating from magnetic flux annihilation, and measurements of plasma anomalous resistivity. Improvements are underway to reduce the main bank crowbar ringing, which will increase the trapped flux in the FRC. A prototype deformable flux-conserving liner with large entrance holes to accept an FRC has also been designed with MACH2 (2-D MHD modelling code) and successfully imploded at Kirtland Air Force Base on the Shiva Star pulsed power facility. (author)