Reduction of ion thermal transport due to non-uniformity effects of the radial electric field at the edge of the JT-60U tokamak

K. Kamiya, K. Itoh, Sanae Itoh

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Non-uniformity effects of the edge radial electric field, E r, on edge transport barrier (ETB) formation have been identified with high-spatiotemporal resolution spectroscopic measurement. We identified the decisive importance of E r-curvature (i.e. 2nd derivative of E r) on ETB formation corresponding to a local peak value in the pedestal region of the normalized ion temperature gradient,LTi-1 ≡ - Ti/Ti. On the other hand, the E r-shear (i.e. 1st derivative of E r) was discovered to promote the expansion of pedestal width, compensating an unfavorable effect of the E r-curvature having its sign dependence on the transport reduction/enhancement - predicted by a theoretical model as LTi-1∞(E'r E'r- ErE''r)0.5. A significant reduction of the inferred ion thermal transport coefficient in the pedestal region, Xiped. , due to the non-uniformity effects of E r was also confirmed quantitatively in the H-mode plasma at the initial ELM-free phase. When the inhomogeneity of radial electric field became strong enough, the inferred Xiped. value was close to its neoclassical one at the later ELM-free H-phase until 1st type-I ELM onset. Nevertheless, we observed the further reduction of electron density fluctuations (in the range up to 300 kHz) and D δsignals in association with the increment of electric field inhomogeneity. These suggest that the electron turbulent transport is suppressed further.

Original languageEnglish
Article number126003
JournalNuclear Fusion
Volume57
Issue number12
DOIs
Publication statusPublished - Sep 11 2017

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nonuniformity
electric fields
inhomogeneity
curvature
ions
ion temperature
temperature gradients
transport properties
shear
expansion
augmentation
high resolution
electrons

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Reduction of ion thermal transport due to non-uniformity effects of the radial electric field at the edge of the JT-60U tokamak. / Kamiya, K.; Itoh, K.; Itoh, Sanae.

In: Nuclear Fusion, Vol. 57, No. 12, 126003, 11.09.2017.

Research output: Contribution to journalArticle

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