Herbert L Berk

TL;DR: In this paper, a fluid model for the flow conditions necessary to form a compact torus from the plasma ejected by a coaxial plasma gun is developed by finding the conditions for which the steady-flow equations break down.

TL;DR: In this article, a kink-tearing eigenmode equation is derived for a slab layer geometry in the limit me/mi≪βi≪L2n/L2s (me/mi ≡mass ratio, βi≡ ion beta value, Ln ≡gradient scale length, Ls ≡shear length) and when the electron collision frequency is comparable to the eigenfrequency.

TL;DR: In this paper, the stability of the scrape-off layer of a tokamak was analyzed, taking into account the surface sheath impedance and the axial shear in the E×B flow.

TL;DR: In this paper, it was shown that Fokker-planck calculations for the nonlinear system abruptly break down in the course of the calculation for some initial conditions, and that this arises because an adiabatic description of phase space structures at zero collisionality does not necessarily lead to continual frequency sweeping.

Abstract: Alternatives to the usual picture of advanced tokamak (AT) discharges are those that form when anomalous thermal conductivity and/or resistivity alter plasma current and pressure profiles to achieve stationary characteristics through self-organizing mechanisms where a measure of desired AT features is maintained without external current-profile control. Regimes exhibiting these characteristics are those where the safety factor (q) evolves to a stationary profile with the on-axis and minimum q ∼ 1. Operating scenarios with fusion performance exceeding H-mode at the same plasma current and where the inductively driven current density achieves a stationary configuration with either small or nonexisting sawteeth should enhance the performance of ITER and future burning plasma experiments. We present simulation results of anomalous current-profile formation and evolution using theory-based hyper-resistive models. These simulations are stimulated by experimental observations with which we compare and contrast the simulated evolution. We find that the hyper-resistivity is sufficiently strong to modify the current-profile evolution to achieve conditions consistent with experimental observations. Modelling these anomalous effects is important for developing a capability to scale current experiments to future burning plasmas.