Scaling of heat transport with beta in the DIII-D tokamak

C. C. Petty, T. C. Luce, J. C. DeBoo, R. E. Waltz, D. R. Baker, M. R. Wade

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

Experiments in the DIII-D tokamak have measured the scaling of heat transport with beta (β) while all other dimensionless parameters are held constant for both H mode and L mode plasmas. Experimental results from the beta scaling of heat transport help to differentiate between various proposed mechanisms of turbulent transport. For L mode plasmas, the beta scaling of heat transport over the range 0.26 ≤ βN ≤ 0.49 is close to zero, with the thermal confinement time scaling as Bτth ∝ β-0.05±0.10 and the effective (or one fluid) thermal diffusivity scaling as χeff ∝ χBβ0.11±0.20. The beta scalings of the ion and electron thermal diffusivities are the same as the effective diffusivity to within the experimental errors. Higher values of beta are investigated in H mode plasmas, where a weak-to-moderate beta scaling of transport is observed over the range 0.8 ≤ βN ≤ 1.7, with the thermal confinement time scaling as Bτth ∝ β0.03±0.11 and the effective thermal diffusivity scaling as χeff ∝ χBβ-0.54±0.21. The ion channel is responsible for the favourable beta scaling of H mode plasmas; the electron channel has no measurable beta dependence. These beta scalings determined by dimensionless parameter scans are much weaker than the predicted beta scalings from the L mode and H mode confinement scaling expressions that are currently being used to predict the performance of ITER.

Original languageEnglish
Pages (from-to)1183-1198
Number of pages16
JournalNuclear Fusion
Volume38
Issue number8
DOIs
StatePublished - 1998

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