A thermal transport coefficient for ohmic and ICRF plasmas in Alcator C-Mod

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:427997

Doughton, W; Coppi, B; Sugiyama, L; Greenwald, M ^[1]; Bombarda, F

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States)

The energy confinement in plasmas produced by Alcator C-Mod machine is markedly different from that observed by previous high field compact machines such as Alcator A and C, FT, and more recently. For ohmic plasmas at low and moderate densities, the confinement times routinely exceed those expected from the so-called neo-Alcator scaling by a factor as high as three. For both ohmic and ICRF heated plasmas, the energy confinement time increases with the current and is approximately independent of the density. The similarity in the confinement between the ohmic and ICRF regimes opens the possibility that the thermal transport in Alcator C-Mod may be described by one transport coefficient for both regimes. The authors introduce a modified form of a transport coefficient previously used to describe ohmic plasmas in Alcator C-Mod. The coefficient is inspired by properties of the so-called ubiquitous mode that can be excited in the presence of a significant fraction of trapped electrons and also includes the constraint of profile consistency. A detailed series of transport simulations are used to show that the proposed coefficient can reproduce the observed temperature profiles, loop voltage and energy confinement time for both ohmic and ICRF discharges. A total of nearly two dozen ohmic and ICRF Alcator C-Mod discharges have been fit over the range of parameter space available using this transport coefficient.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• OSTI ID: 427997
• Report Number(s): CONF-960634--
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALCATOR DEVICE
HEAT TRANSFER
ICR HEATING
JOULE HEATING
MODIFICATIONS
PLASMA SIMULATION
TEMPERATURE DISTRIBUTION