Showing papers by "Marshall N. Rosenbluth published in 1976"

Parametric decay of electromagnetic waves into two plasmons and its consequences

Abstract: The parametric decay of the laser radiation into two plasma waves at the quarter critical density of an inhomogeneous plasma is analyzed. The growth rate and threshold of the absolute instability are derived. The bound on the saturation level of the plasma waves is obtained from the consideration of the pump depletion. The scattered radiation at 3/2 ω0 due to the beating of the incident wave with the backward plasma wave is calculated and compared with observations.

Numerical studies of nonlinear evolution of kink modes in tokamaks

Abstract: A set of numerical techniques for investigating the full nonlinear unstable behavior of low‐β kink modes of given helical symmetry in tokamaks is presented. Uniform current density plasmas display complicated deformations including the formation of large vacuum bubbles provided that the safety factor q is sufficiently close to integral. Fairly large m=1 deformations, but not bubble formation, persist for a plasma with a parabolic current density profile (and hence shear). Deformations for m⩾2 are, however, greatly suppressed.

Single‐mode saturation of the bump‐on‐tail instability: Immobile ions

Abstract: A one‐dimensional collisionless electron plasma is considered with a velocity distribution of the ’’bump‐on‐tail’’ type. The ions are immobile and the eigenmodes are separated by finite periodic boundary conditions. The electron number density is increased above the neutral‐stable value by a small fractional amount Δ. A single mode moves on to the positive slope region and grows until saturated at small amplitude by nonlinear effects. The saturated amplitude, frequency shift, and modified electron distribution function are determined in terms of Δ. The solution is shown to be stable and conserves energy and momentum. All singular functions appearing in higher harmonics are identified as generalized functions, and a correction to the class 1c mode adjoint is obtained. The solution of the ’’inflection‐on‐tail’’ problem is also given.

Dissipative universal instability due to trapped electrons in toroidal systems and anomalous diffusion

Abstract: Drift wave instabilities in toroidal systems arising from collisions of trapped electrons are analyzed including the effects of a sheared magnetic field. A maximum bound on the turbulent transport is estimated, and the theoretical predictions compared with experimental results from the Princeton FM‐1 spherator.

Cross-field energy transport by plasma waves

Abstract: Energy transport across a magnetic field by plasma and ion waves is shown to be an important process even in thermal equilibrium, because their propagation is uninhibited by the magnetic field and their long mean free path.

Nonlinear growth of the M = 1 tearing mode

Abstract: Numerical results are presented for the nonlinear evolution of the tearing mode with poloidal mode number one. Nonlinearly, the mode continues to grow exponentially at approximately the linear growth rate until it flattens the toroidal current inside the singular surface and increases the safety factor to unity at the plasma center. The hypothesis that the mode causes the internal disruption in tokamaks is supported by the fact that the time scale for the process agrees with experiment.

Conference and Symposia Plasma Physics and Controlled Nuclear Fusion Research: Summaries of the 6. International Conference

Abstract: Some 65 of the 150 papers presented at this excellently organized and planned Conference reported new experimental information on the magnetic confinement of high-temperature matter. Contrary to some fears that the reduction to two years of the interval between Conferences would lead to a paucity of new material, these papers ' reported important new advances in several areas; and the Conference was both timely and fruitful.