Global particle confinement in the Texas Experimental Tokamak

Abstract

Particle transport in an ohmically heated tokamak plasma was investigated in the Texas Experimental Tokamak (TEXT). Spectroscopic measurements of the electron source were used with electron density measurements to derive particle confinement times from the continuity equation. Scalings were developed for particle confinement time with electron density, plasma current, toroidal field, and plasma positioning. Simultaneous measurement of electrostatic fluctuations with Langmuir probes may suggest a correlation between edge particle transport in TEXT and electrostatic turbulence. In addition, two major features of transport were isolated. First, transport is poloidally asymmetric at least in the plasma edge. Secondly, in some cases, the particle confinement scalings are closely associated with the scalings for recycling at particular surfaces. Similarities of the TEXT global particle confinement time scalings to those observed in other tokamaks may allow the conclusions of this work to be extended to other devices.

Computation of electromagnetic turbulence and anomalous transport mechanisms in tokamak plasmas

“…These scales are roughly commensurate with the typical scales of low frequency drift motion as defined below. Moreover, transport analysis by power balance reveals an "anomalous transport" which is in good agreement with what one infers from these probe measurements [3]. Although there is much disagreement concerning just what mechanism accounts for this turbulence and transport, it is to be recognised that the fact that on account of these measurements we know with some confidence that anomalous transport is caused by such low frequency drift turbulence constitutes one of the major advances in the science of magnetic plasma confinement of recent years.…”

Studies of plasma performance and transport in the advanced toroidal facility (ATF)

“…The observations are broadly similar to those from the TEXT tokamak [5][6][7]. Coupling of the electrostatic turbulence to a radiative instability is expected theoretically in tokamaks [8], and a similar mechanism has been proposed for ATF.…”

Suppression of Temperature Fluctuations and Energy Barrier Generation by Velocity Shear

“…Such barriers develop spontaneously in a wide variety of magnetically confined plasmas, producing transitions from a low energy confinement state (L mode) to a higher energy confinement state (H mode) [1]. The L-H transition in magnetically confined plasmas is accompanied by a reduction of turbulence levels [2], confirming the paradigm that microturbulence is responsible for a considerable part of the energy and particle losses [3]. Behavior similar to that of the spontaneous L-H transition is obtained by applying an external radial electric field to the plasma using an electrode [4], indicating that the radial electric field and resulting E 3 B rotation play a crucial role.…”