Thomas P Intrator

Summary form only given. The generation and destruction of magnetic field is an important feature of solar, magnetosphere and cosmic plasmas, for example during reconnection, dynamo, and turbulent processes. We have experimentally measured spatially resolved profiles of magnetic flux ropes. These data include ion flow, magnetic field, current density, and plasma pressure, which allow us to verify a screw pinch equilibrium and also infer the electron fluid flow in three dimensions. Parallel currents along each flux rope result in a mutual attraction, which compresses and distorts the cylindrically symmetric equilibrium profiles. The electron and ion fluid flows turn out to be different, and we show that sheared axial electron fluid flow v_e generates magnetic field B(t) via the induction term curl X̅v_e X B = -curl X E = dB/dt. Data show a quadrupole out of plane magnetic field signature with four fold symmetry that is driven by flux rope flows with two fold symmetry. This mechanism provides a natural and general mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence.

Summary form only given. The objective of the Field-Reversed Configuration Heating Experiment (FRCHX) is to obtain a better understanding of the fundamental scientific issues associated with high energy density plasmas (HEDPs) in strong, closed-field-line magnetic fields. These issues have relevance to such topics as magneto-inertial fusion (MIF), laboratory astrophysical research, and intense radiation sources, among others. To create the HEDP, a field-reversed configuration (FRC) plasma of moderate density is first formed via reversed-field theta pinch. It is then translated into a cylindrical aluminum shell (solid liner), where it is trapped between two magnetic mirrors and then compressed by the magnetically-driven implosion of the shell. A requirement is that once the FRC is stopped within the shell, the trapped flux inside the FRC must persist while the compression process is completed. With the present shell dimensions and drive bank parameters, the total time required for implosion is ~25 microseconds. Lifetime measurements of recent FRCHX FRCs indicate trapped lifetimes now approaching ~14 microseconds, and with recent experimental modifications the liner compression can be initiated considerably earlier before formation is completed in order to close that gap further. A discussion of FRC lifetime-limiting mechanisms will be presented along with a description of FRCHX and recent changes that have been made to it. Results from recent experiments aimed at lengthening FRC lifetime will also be presented.

Summary form only given. The Field-Reversed Configuration Heating Experiment (FRCHX) is a collaborative experiment between the Air Force Research Laboratory (AFRL) and Los Alamos National Laboratory (LANL) to explore the physics of magneto-inertial fusion (MIF) and other high energy density laboratory plasma (HEDLP) phenomena. In the experiment, a plasma in a field-reversed configuration (FRC), with density 5 × 10 16 ions/cm 3 , total temperature ~200 eV, poloidal magnetic field ~1 T, length 15 ~ 20 cm, and field exclusion radius ~2 cm is formed via a reversed-field theta discharge and then translated a short distance (~1 m) into a magnetic mirror that has been established within a 30 cm long, 10 cm diameter, 0.11 cm thick aluminum solid liner. The high energy density state (10 19 ions/cm 3 , multi-keV, MegaGauss fields) will be achieved when a 12 MA axial current, provided by the AFRL Shiva Star capacitor bank, implodes the liner and compresses the FRC within. Conventional FRC formation techniques trap only a small fraction of the initial axial bias field. Guided by extended 2D-MHD simulations, several factors limiting the closed field lifetime of the FRCs to about half that required for good liner compression have been identified, and new experimental hardware has been designed and prepared to increase that lifetime. Results from recent setup experiments will be presented, including a full-scale engineering test shot, along with a description of FRCHX's pulsed power systems and plasma diagnostics.

Summary form only given. The goal of the Field-Reversed Configuration Heating Experiment (FRCHX) is to demonstrate magnetized plasma compression and thereby provide a low cost approach to high energy density laboratory plasma (HEDLP) studies, which include such topics as magneto-inertial fusion (MIF). A requirement for the field-reversed configuration (FRC) plasma is that the trapped flux in the FRC must maintain confinement of the plasma within the capture region long enough for the compression process to be completed, which is approximately 20 microseconds for FRCHX. Current lifetime measurements of the FRCs formed with FRCHX show lifetimes of only 7 ~ 9 microseconds once the FRC has entered the capture region.

Summary form only given. Experiments on FRC formation and translation into the interior of a metal shell or liner have been conducted at AFRL. Flux exclusion, collimated light, and interferometer data on magnetized plasma injection will be presented. These are a pre-requisite for FRC compression by liner implosion, experiment progress on which will also be presented. FRC translation, capture, and compression experiments all use primarily axial ~ 2 Tesla guide and mirror fields established inside the liner, using ~ 5 millisecond rise time discharges into an array of pulsed magnet coils surrounding the liner implosion portion of the device. A 12 MA, 4.5 MJ axial discharge drives the liner implosion for compression experiments. The FRC capture experiments use 3 capacitor discharges into a segmented theta coil surrounding the FRC formation region to establish a bias field, accomplish pre-ionization of deuterium gas, and provide the reverse field main theta discharge (~ 1 Megamp) which forms the FRC. This is aided by two cusp field discharges. The guide and mirror fields enable translation of the FRC and its capture in the liner interior region. Diagnostics include pulsed power (current and voltage), magnetic field, field exclusion, He Ne laser interferometry, imaging and spectroscopy, radiography, and both activation and time-of-flight neutron detection. Design features and operating parameters are guided by 2D-MHD simulations.

Summary form only given. Over the past six years, the Air Force Research Laboratory in Albuquerque, NM has been working in close collaboration with Los Alamos National Laboratory on their field-reversed configuration (FRC) experiment, FRX-L. Through these joint efforts a second experiment has been designed and is now being assembled and tested at the AFRL. This new experiment, which is referred to as the FRC Heating Experiment (FRCHX), has the goal of not only forming a plasma in a field-reversed configuration but of also translating it into an aluminum flux conserving shell (solid liner), where it will be subsequently heated through rapid compression of the liner. The FRC formation portion of FRCHX has been designed to closely match the electrical properties of FRX-L so that FRCs of similar parameters can be formed. Likewise, the translation portion of FRCHX, which has been designed and fabricated concurrently with the new translation section of FRX-L, also closely matches that of FRX-L. The design approach being taken to compressively heat the FRC in the final portion of FRCHX relies on the experimental setup used during two earlier "deformable-contact" vacuum liner experiments that were performed with the Shiva Star Capacitor Bank. In these experiments the liner electrodes had 8-cm-diameter holes on their axes, and both tests were found to be successful in that the ends of the 10-cm diameter, 30-cm long aluminum liner stretched and maintained contact with the electrodes while the body of the liner glided radially inward to implode uniformly. This presentation focuses on the system design and integration of the first two portions of the FRCHX experiment, the FRC formation and translation sections. The performance characteristics of each, as determined by recent test results, are discussed, along with the various magnetic and plasma diagnostics that are being fielded in both sections. Remaining tasks to be accomplished before a complete FRC formation, translation, and compression experiment can be performed are also outlined at the end.