TY - JOUR
T1 - Reduction of ion thermal transport due to non-uniformity effects of the radial electric field at the edge of the JT-60U tokamak
AU - Kamiya, K.
AU - Itoh, K.
AU - Itoh, S. I.
N1 - Funding Information:
The authors deeply appreciate the continued research and operational efforts of the entire JT60 team. Discussions with Prof K. Ida, Dr T. Kobayashi, Prof P.H. Diamond, Prof U. Stroth and Prof J.Q. Dong are also acknowledged. Authors acknowledge the partial support by GrantinAid for Scientific Research (JP 15K06657, JP 15H02155, JP 16H02442) and collaboration programmes between QST and universities and of the RIAM of Kyushu University, and by Asada Science Foundation.
PY - 2017/9/11
Y1 - 2017/9/11
N2 - 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.
AB - 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.
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U2 - 10.1088/1741-4326/aa7f3b
DO - 10.1088/1741-4326/aa7f3b
M3 - Article
AN - SCOPUS:85034445469
SN - 0029-5515
VL - 57
JO - Nuclear Fusion
JF - Nuclear Fusion
IS - 12
M1 - 126003
ER -