Dependence of the DIII-D beta limit on the current profile

Conference · Mon Apr 01 04:00:00 EST 1991

OSTI ID:5905988

Strait, E J; Chu, M S; Ferron, J R; Lao, L L; Osborne, T H; Taylor, T S; Turnbull, A D ^[1]; Lazarus, E A ^[2]

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1. General Atomics, San Diego, CA (USA)
2. Oak Ridge National Lab., TN (USA)

The maximum beta values achieved in DIII-D are not fully described by the simple scaling law {beta}{sub max} {proportional to} I/aB. There is, in addition, a dependence on the form of the current profile as parameterized by the safety factor q and internal inductance {ell}{sub i}. The maximum experimentally achieved value of normalized beta {beta}{sub N} = {beta}/(I/aB) varies from 3.5 at low safety factor q (q{sub 95} < 3) to 5 at higher values of q. At low q, discharges are terminated by disruptions at high {beta}{sub N} and at both the low and high {ell}{sub i} boundaries of the stable range. These disruptions are attributed to external and global kink modes. At higher q, such disruptions are much less frequent, and beta is limited by slowly growing resistive modes, fishbones, and possibly by ballooning modes. At each value of q, the maximum beta tends to increase with internal inductance {ell}{sub i}. A numerical study of kink mode stability has shown a similar trend for optimized pressure profiles. These observations have suggested a new scaling law for the operational beta limit: {beta}{sub max} = 4{ell}{sub i}(I/aB), which fits the DIII-D data well. 13 refs., 4 figs.

• Research Organization: General Atomics, San Diego, CA (USA)
• Sponsoring Organization: DOE; USDOE, Washington, DC (USA)
• DOE Contract Number: AC03-89ER51114; AC05-84OR21400
• OSTI ID: 5905988
• Report Number(s): GA-A-20477; CONF-910609--7; ON: DE91011140
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700103* -- Fusion Energy-- Plasma Research-- Kinetics
BETA RATIO
CURRENT DENSITY
DIVERTORS
DOUBLET REACTORS
INSTABILITY
PLASMA DISRUPTION
PLASMA INSTABILITY
SCALING LAWS
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS