The effect of current profile changes on confinement in the DIII-D tokamak

Conference · Fri May 01 04:00:00 EDT 1992

OSTI ID:7205694

Ferron, J R; Lao, L L; Taylor, T S

Experiments in the DIII-D tokamak have demonstrated that the effect of changes in the current profile on plasma confinement varies with the discharge shape. The results are similar in many respects to those from other tokamaks. In all cases, a rapid change in the plasma current in an L-mode, circular or moderately elongated, discharge has been used to produce a transient change in the current density profile. Although the detailed results vary among tokamaks, it is generally observed that during and immediately following a negative plasma current ramp, the stored energy does not follow the L-mode scaling that predicts that confinement should be proportional to the total plasma current. The stored energy changes on the time scale of the relaxation of the current density profile rather than the shorter time scales of the energy confinement time or the change in the total current. Because of the discharge having capability of the DIII-K tokamak it has been possible to extend these current ramp experiments beyond the L-mode, moderate elongation case to highly elongated double-null divertor discharges in H-mode. In separate experiments, a rapid change in the discharge elongation has also been used to vary the current density profile. This paper shows that the dependence of the plasma confinement on the current profile changes when the discharge shape is changed. This variation with discharge shape provides evidence for a model that predicts that changes in the local magnetic shear resulting from the changes in the current profile can result in decreased local transport.

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-89ER51114
• OSTI ID: 7205694
• Report Number(s): GA-A-20913; CONF-920610--7; ON: DE92016256
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700310* -- Plasma Confinement-- (1992-)
CLOSED PLASMA DEVICES
CONFINEMENT
CONFINEMENT TIME
CURRENT DENSITY
DIVERTORS
DOUBLET-3 DEVICE
H-MODE PLASMA CONFINEMENT
PLASMA CONFINEMENT
THERMONUCLEAR DEVICES
TOKAMAK DEVICES