[en] Topics covered at this meeting are: computational plasma physics; slow wave devices; basic phenomena in fully ionized plasmas; microwave-plasma interactions; space plasmas; fast wave devices; plasma processing; plasma, ion, and electron sources; vacuum microelectronics; basic phenomena in partially ionized gases; microwave systems; plasma diagnostics; magnetic fusion theory/experiment; fast opening switches; laser-produced plasmas; dense plasma focus; intense ion and electron beams; plasmas for lighting; fast z-pinches and x-ray lasers; intense beam microwaves; ball lightning/spherical plasma configuration; environmental plasma science; EM and ETH launchers; and environmental/energy issues in plasma science. Separate abstracts were prepared for most of the individual papers

[en] Thompson et.al. reported on a new Z-pinch load termed a tandem puff. In this geometry, current from a Marx bank is initially carried by an annular plasma column. Magnetohydrodynamic forces push the current sheath axially. At the end of the conduction region, the current is transferred onto an annular gas puff without an intervening vacuum power flow volume. The puff then implodes much like a standard Z-pinch. The advantages of this geometry are (1) it uses a simple, compact and relatively inexpensive Marx bank, (2) a separate plasma opening switch (POS) is not needed between the source and the load, and (3) Z-pinch parameters like mass loading and radius need not be tuned to match the Marx bank's current time history. The authors present here initial tests of this tandem puff configuration using the 4 MJ ACE 4 inductive energy storage (IES) machine. Neon and a few krypton puffs from an 11 centimeter diameter fast gas valve gave significant (>10 kJ) soft x-ray (∼1 keV) yields. Load currents exceeded 3 megamps, a level 3 times higher than the earlier experiments. They observed implosion times of over 400 nanoseconds. The diagnostics included calorimeters, time-resolved sensors (PCDs, XRDs, and silicon PIN diodes), and time-integrated images (pinhole and KAP spectra). Only a limited number of shots were made, hence this configuration is far from optimized. However, the results suggest that the tandem puff geometry is very promising as a long implosion time x-ray source

[en] Prior experiments showed enhanced soft (∼1 keV) and significant hard (>6 keV) x-ray output for aluminum plasma jet implosions that included a central metal wire. In an effort to confirm those results and to establish the operative physical processes, the authors adapted the puff-on-wire geometry to the tandem puff load on the 4 MJ ACE 4 inductive energy storage (IES) machine. Most of the experiments used an 11 centimeter diameter neon gas puff surrounding central fine (25--75 micron diameter) wires of copper, molybdenum, silver and tungsten. In addition to standard soft radiation sensors (calorimeters, XRDs, PCDs, etc.), the diagnostics included a nine channel silicon PIN diode spectrometer covering the range from ∼6 to over 300 keV. Peak current into the load exceeded 3 megamps. The authors do not see increased soft and hard x-ray output when a central wire is in place. Time resolved data show that the soft and hard x-ray components begin at the same time but their evolutions vary with wire atomic number. The time scale of the hard radiation exceeds 100 ns. The hard x-ray yield increases with wire atomic number

[en] The transient sheath expansion induced by a voltage pulse applied to two-dimensional targets is simulated numerically with a fluid model. Non-linear sheath expansion due to sheath overlapping in a small cylindrical bore with a finite depth is presented. The sheath expansion inside the bore is enhanced by the initially nonuniform plasma distribution. The angular distribution of the ions impinging on the target surface and the nonuniformity of the incident ion dose are calculated for a cylindrical bore target. A dip of the dose profile, seen earlier for square targets, appears at convex corners of the target. This dip is a numerical artifact, not a real physical phenomenon, mainly caused by false diffusion (numerical diffusion) and inaccurate estimation of the electric field on the corner. By re-orientation of the numerical mesh to suppress false diffusion, the dip effect can be eliminated effectively in the square target case

[en] The build-up of an adequate model for the mechanism of charged particle acceleration is one of the urgent problems in the plasma focus studies. It is known that near-electrode processes play an important role in the case of a solid anode. The goal of a given study was to investigate the dynamics of the electron beam and the spectrum of the hard X-ray (HXR) produced in the current sheath run away regime within the plane geometry of electrodes. For studying the HXR-spectrum a four channel circuit of measurements was used. Each channel is a combination of a fast plastic scintillator (t < 0.5 ns) with a photoelectron converter (t < 0.3 ns). The radiation under study is introduced into the detector shielded against the electromagnetic noise and against the scattered radiation through various filters. The detectors were placed symmetrically, at the same distances from the anode. The control over the discharge symmetry and over the homogeneity of a radiation field in each discharge was realized with the thermoluminescent dosemeters and with a pin-hole camera. The X-ray spectra at each instant of time was reconstructed from the experimental absorption curves by the modified regularization technique

[en] Knowledge of the internal magnetic field profile in hot plasmas is fundamental to understanding the structure and behavior of the current profile. The transient internal probe (TIP) is a novel diagnostic designed to measure internal magnetic fields in hot plasmas. The diagnostic involves shooting a magneto-optic probe through the plasma at high velocities (greater than 2 km/s) using a two stage light gas gun. Local fields are obtained by illuminating the probe with an argon ion laser and measuring the amount of Faraday rotation in the reflected beam. Initial development of the diagnostic is complete. Results of magnetic field measurements conducted at 2 km/s will be presented. Helium muzzle gas introduction to the plasma chamber has been limited to less than 0.4 Torr-ell. Magnetic field resolution of 40 Gauss and spatial resolution of 5 mm have been achieved. System frequency response is 10 MHz

[en] Fluid models for toroidal plasma are considered paying particular attention to the effects of particle motion along the equilibrium magnetic field. It is shown that the basic fluid equations can be obtained either as moments of the drift-kinetic equation, or from the standard fluid equations by expanding them in 1/B small parameter. It is shown that the collisionless gyroviscosity accounts for the effects of the particle magnetic drift in the parallel component of the momentum balance equation. Simple truncated model of the plasma response for arbitrary ω_D (magnetic drift frequency) and k_parallelV_t (parallel transit frequency) is proposed. In the absence of resonances, which can be inhibited by the particle magnetic drift, this model recovers the exact kinetic results with satisfactory accuracy. In general case, the kinetic closure for the effects of the particle motion along the magnetic field is suggested in terms of the parallel viscosity and the heat flux. They are directly calculated from the linear drift-kinetic equation. Simplified expressions in the different asymptotic limits are derived

[en] Recent ideas concerning inertial-electrostatic confinement (IEC) of fusion plasmas coupled with recent experimental results have motivated looking at the problem of confinement of these plasmas in both the gridded (pure electrostatic) and magnetically assisted (via confinement of high beta plasmas in a magnetic cusp) configuration. Questions exist as to the nature of the potential well structure and the confinement properties of high beta plasmas in magnetic cusp configurations. This work focuses on the magnetically assisted concept known as the Polywell trademark. Results are reported on the numerical simulation of IEC plasmas aimed at answering some of these questions. In particular the authors focus on two aspects of the Polywell, namely the structure of the magnetic cusp field in the Polywell configuration and the nature of the confinement of a high beta plasma in a magnetic cusp field. The existence of line cusps in the Polywell is still in dispute. A computer code for modeling the magnetic field structure and mod-B surface has been written and results are presented for the Polywell. Another source of controversy is the nature of the confinement of a high beta plasma in a magnetic cusp, and in particular in the polywell. Results from 2-D Particle In Cell (PIC) simulations aimed at answering some of these questions are presented

[en] The first experimental evidence of low frequency current drive in a tokamak has been observed on the Phaedrus-T tokamak. Low frequency current drive utilizes waves with frequencies below the ion cyclotron frequency to inject momentum to electrons to drive a toroidal current, and is often referred to as Alfven wave current drive (AWCD). Like other noninductive current drive techniques, AWCD would allow fusion tokamak reactors to operate as steady state devices. AWCD would also allow tailoring of the energy and current density profiles. Properly modified profiles would make the plasma less susceptible to instabilities. The presence of noninductive current is inferred from the behavior of the plasma loop voltage measured at the edge of the plasma. For the experiments presented here, the principle evidence of AWCD is a fractional loop voltage drop of 0.35 that cannot be accounted for by a decrease in plasma resistivity or stored magnetic energy. The estimated driven current is 20--35 kA out of a total 64 kA. Furthermore, the ΔV_L is approximately linear with applied RF power and ΔV_L is dependent upon the phase of the antenna

[en] Convergent ion focus devices have been considered as sources of fusion reactivity since early studies in the late 1960's. In general, these devices rely on the confinement and acceleration of plasma ions in a spherically or cylindrically symmetric electrostatic potential well. Ions at the edge fall into the well and converge to the central core region. This leads to a strongly increasing central density and central ion energies comparable to the depth of the potential well, resulting in considerable fusion reactivity with modest device parameters. Several schemes have been proposed for creating the potential well, with simple transparent spherical grids being the usual experimental realization. Potential applications of these fusion devices range from small low-intensity fusion-product particle sources for nuclear assaying to more intense sources for isotope generation and waste processing. Even more optimistic projections have led to discussions of fusion power generation through electrostatic confinement. Recent experiments and modeling efforts are developing a deeper understanding of the operation of these devices. Operation of a gridded spherical focus at low density has verified the classical ion flow model and demonstrated a core density enhancement factor of > 10. Probe measurements with applied potentials of ≤ 10 kV indicate a space potential distribution which is much steeper than that expected from simple space-charge-limited flow. The highest gradients are in the near-field region of the grid where the angular asymmetries of the potential distribution are also highest. Even so, central core radii of < 0.6 cm have been observed, considerably below the radius expected from single ion orbit models. Near-term future experiments are concentrating on development of nonperturbing diagnostics of the energetic ion core, achieving high core density operation, and testing predictions of flow instabilities