Traveling mirror compressor delay line with nonconstant capacitance

The scaling relations for a traveling mirror magnetic compressor [P.M. Bellan, Phys. Rev. Lett. 43, 858 (1979)] having nonconstant capacitance are derived. Varying capacitance (rather than inductance) makes possible a lower impedance device, and hence, higher field levels or faster compression times

Alfvén-Wave Instability of Current Sheets in Force-Free Collisionless Plasmas

If the current sheet between adjacent twisted magnetic flux tubes is sufficiently thin, the electron flow velocity becomes comparable to the Alfvén velocity and can destabilize collisionless Alfvén waves. The threshold for instability in force-free plasmas is calculated for both inertial and kinetic Alfvén-wave regimes. When there is strong magnetic shear, unstable kinetic Alfvén waves can resonantly accelerate ions to energies much higher than the electron temperature

Collisionless reconnection using Alfvén wave radiation resistance

Patchy magnetic reconnection involves transient field-aligned current filaments. The spatial localization, transient time-dependence, and orientation of these current filaments means they must radiate torsional Alfvén waves. Radiation of wave energy does not come for free—it must load the current which acts as the radiative source. This loading (radiation resistance) is proposed as the energy sink required for collisionless magnetic reconnection to proceed. Radiation resistance for both inertial and kinetic Alfvén waves is calculated and, for highly collisionless plasmas, is shown to exceed by a substantial factor both Spitzer resistivity and the effective resistance due to the direct acceleration of electrons (inertial loading). The radiation resistivity is shown to provide the magnetic field diffusivity required for magnetic fields to diffuse across the assumed width of the current filament on the time scale of the reconnection. It is also shown that Landau damping of the radiated waves results in the generation of energetic, field-aligned particles: in the beta << me/mi regime the energetic particles are electrons while in the me/mi << beta << 1 regime, the energetic particles are ions

Laboratory investigations of space-relevant, self-organizing MHD plasmas

Pulsed power technology is used to produce transient MHD-regime plasmas having topology and dynamical behavior similar to solar and astrophysical plasmas. These plasmas are not exact scale models, but exhibit many behaviors similar to actual solar and astrophysical plasmas, for example, collimation, kinking, and jet motion. These plasmas can also display an interaction between MHD-dynamics and non-MHD particle orbit behavior

Miniconference on astrophysical jets

This miniconference brought together observers of astrophysical jets, analytic and numerical modelers of both astrophysical jets and spheromaks, and laboratory experimentalists. The purpose of the miniconference was to encourage interaction between these diverse groups and also expose the plasma physics community to the interesting plasma issues associated with astrophysical jets. The miniconference emphasized magnetically driven astrophysical jets and consisted of three half-day sessions. The order of presentation was approximately: observations and general properties, experiments, numerical models, and special topics

Comment on "On the Alfvén resonance and its existence" [Phys. Plasmas 2, 340 (1995)]

The validity of the Alfvén resonance concept in a real plasma is discussed since experiments are performed on real plasmas and not on MHD plasmas

Simple system for locating ground loops

A simple low-cost system for rapid identification of the cables causing ground loops in complex instrumentation configurations is described. The system consists of an exciter module that generates a 100 kHz ground loop current and a detector module that determines which cable conducts this test current. Both the exciter and detector are magnetically coupled to the ground circuit so there is no physical contact to the instrumentation system under test

Rotamak confinement-power-current relationships and r.f. loading resistance

The relationships between input power, driven current, energy confinement, temperature and density are examined in detail for existing rotamak experiments. Additionally, the loading resistance presented to the r.f. power supply and the density at which this resistance peaks are calculated (for typical experiments this density corresponds to an optimum operating point since maximum power is coupled to the plasma)

Conservation of canonical circulation and its relation to finite Hall term magnetohydrodynamics

The axisymmetric, compressible visco-resistive two-fluid plasma equations are examined under the constraint that the current is purely poloidal and the pressure is a function of density only ("barotropic"). For ideal plasmas (zero resistivity and zero viscosity) the Kelvin circulation theorem of fluid mechanics and the concept of frozen-in field lines turn out to be limiting cases of a more general concept, namely, that the canonical circulation Ssigma=[contour-integral] (msigmausigma+qsigmaA) ·dl of a toroidal fluid element, is exactly conserved as the toroidal element convects and/or is compressed. Appropriate linear combinations of the electron and ion fluid equations give a magnetohydrodynamic vorticity transport equation and an induction equation with a nonlinear Hall term. The finite Hall term is identical to the source term in the vorticity transport equation [P. M. Bellan, Phys. Rev. Lett. 69, 3515 (1992)], except for a constant factor related to the ion collisionless skin depth

Simple system for mapping magnetic field errors in tori

A simple inexpensive electron beam/detector system is described. This system is capable of making vector maps of magnetic field errors over the minor cross section of toroidal plasma devices