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 language | English |
---|---|
Pages (from-to) | 1183-1198 |
Number of pages | 16 |
Journal | Nuclear Fusion |
Volume | 38 |
Issue number | 8 |
DOIs | |
State | Published - 1998 |