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[en] Realistic FRC equilibria are calculated and their stability to the n=1 tilting mode is studied. Excluding kinetic effects, configurations ranging from elliptical to racetrack are unstable. Particle simulations of FRCs show that particle loss on open field lines can cause sufficient plasma rotation to drive the n=2 rotational instability. The allowed frequencies of the shear Alfven wave are calculated for use in heating of spheromaks. An expanded spheromak is introduced and its stability properties are studied. Transport calculations of CTs are described. A power balance model shows that many features of gun-generated CT plasmas can be explained by the dominance of impurity radiation. It is shown how the Taylor relaxation theory, applied to gun-generated CT plasmas, leads to the possibility of steady-state current drive. Lastly, applications of accelerated CTs are considered. (author)
[en] Current-induced precessional magnetization reversal in microscopic spin valves is studied. The magnetization reversal is induced by ultra-short in-plane current pulses through the device. The resulting transverse Oerstedt field triggers precessional magnetization reversal of the free layer. Consecutive application of the same current pulse toggles the magnetization with every pulse. The bias field dependence of the switching properties reveals the clear characteristics of precessional switching
[en] The relationship of the micromagnetic structure, the contributions of various crystalline phases and hysterons obtained by the first order reversal curves (FORC) method in sintered (NdDy)(FeCo)B magnets is discussed. The distribution map of parameters of magnetic hysteresis partial loops that allows the separation of various spin ensembles to the magnetization has been built.
[en] The shape and the dynamics of reversals of the magnetic field in a turbulent dynamo experiment are investigated. We report the evolution of the dipolar and the quadrupolar parts of the magnetic field in the VKS experiment, and show that the experimental results are in good agreement with the predictions of a recent model of reversals: when the dipole reverses, part of the magnetic energy is transferred to the quadrupole, reversals begin with a slow decay of the dipole and are followed by a fast recovery, together with an overshoot of the dipole. Random reversals are observed at the borderline between stationary and oscillatory dynamos.
[en] Rapid field reversal is employed to trap an initial negative-magnetic-field bias flux in a 300-cm long theta pinch having an inner radius of 10 cm. A large fraction (40%--75%, depending on filling pressure) of the initial bias flux is trapped after the implosion (approx.1 μsec); this fraction then diminishes to a plateau value of 25% to 35% in approximately 2 μsec. During this decay, magnetic probe measurements indicate an average anomalous resistivity one order of magnitude greater than classical. The open-line configurations obtained have large separatrix (zero enclosed flux) radii and are present for the duration of the applied magnetic field. The presence of the reversed bias field lowers the plasma temperature by a factor of two
[en] Bias field scans are performed at various fill pressures in the FRX-C [Fusion Technol. 9, 13 (1986)] and FRX-C/LSM [Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1989), Vol. II, p. 517] field-reversed theta pinches. These data show a systematic degradation of the confinement properties of field-reversed configurations whenever strong axial implosions occur during plasma formation. This limitation prevents access to the desired regime of large-size and long-lived field-reversed configurations. The cause of the confinement degradation must be due to some formation or gross stability problem. Here many studies are reported that attempt to correlate confinement degradation with some formation characteristic. These investigations remain inconclusive and suggest further stability studies presented in a companion paper
[en] Highly elongated field-reversed configuration (FRC) equilibria are computed in a straight conducting cylinder for the pressure profile p'(psi) = cH(psi), where H(x) is the Heaviside function. The equilibria are found by inverting the Grad--Shafranov equation by means of a Green's function and by solving the resulting nonlinear integral equation. Long equilibria are obtained only for values of the constant c very near a critical value: the equilibria change from 2:1 elongated to infinitely long as c varies by only 0.3%. This criticial value of c is predicted by the average beta condition