On the Origin of Steep and Localized Radial Electric Field in the Transport Barrier at Plasma Edge

Itoh, K.; Itoh, Sanae I.; Kobayashi, Tatsuya; Kamiya, K.; Ido, T.; Tokuzawa, T.; Inagaki, S.; Kasuya, Naohiro

doi:10.1002/ctpp.201610042

Cited by 2 publications

(3 citation statements)

References 52 publications

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“…The model of turbulence intensity, in the presence of inhomogeneous radial electric field, was assessed based on the model formula for the effect of electric field shear 5 12 13 and that of electric field curvature in 31 32 , and is used in the experimental test here as;…”

Section: Resultsmentioning

confidence: 99%

Experimental validation of non-uniformity effect of the radial electric field on the edge transport barrier formation in JT-60U H-mode plasmas

Kamiya

Itoh

2016

Sci Rep

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The turbulent structure formation, where strongly-inhomogeneous turbulence and global electromagnetic fields are self-organized, is a fundamental mechanism that governs the evolution of high-temperature plasmas in the universe and laboratory (e.g., the generation of edge transport barrier (ETB) of the H-mode in the toroidal plasmas). The roles of inhomogeneities of radial electric field (Er) are known inevitable. In this mechanism, whether the first derivative of Er (shear) or the second derivative of Er (curvature) works most is decisive in determining the class of nontrivial solutions (which describe the barrier structure). Here we report the experimental identification of the essential role of the Er-curvature on the ETB formation, for the first time, based on the high-spatiotemporal resolution spectroscopic measurement. We found the decisive importance of Er-curvature on ETB formation during ELM-free phase, but there is only a low correlation with the Er-shear value at the peak of normalized ion temperature gradient. Furthermore, in the ELMing phase, the effect of curvature is also quantified in terms of the relationship between pedestal width and thickness of the layer of inhomogeneous Er. This is the fundamental basis to understand the structure of transport barriers in fusion plasmas.

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Section: Resultsmentioning

confidence: 99%

Experimental validation of non-uniformity effect of the radial electric field on the edge transport barrier formation in JT-60U H-mode plasmas

Kamiya

Itoh

2016

Sci Rep

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“…We here briefly revisit theoretical formulas for experimental validation, which have been proposed based on the recent progress of diagnostics [20][21][22][23]. In this study, we use the model of normalized turbulence intensity, I/I 0 , in the presence of nonuniformity E r effects (as expressed by the parameter of Z) as follows:…”

Section: Theoretical Modelmentioning

confidence: 99%

“…As discussed in [20][21][22], the nonlinear decorrelation rate of fluctuations is enhanced by the shear of the radial electric field as…”

Section: Theoretical Modelmentioning

confidence: 99%

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

Kamiya

Itoh

2017

Nucl. Fusion

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Nonuniformity effects of the edge radial electric field, E r , on edge transport barrier (ETB) formation have been identified with highspatiotemporal 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, L −1 Ti ≡ −∇T i /T i . 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. A significant reduction of the inferred ion thermal transport coefficient in the pedestal region, χ i,ped. , due to the nonuniformity effects of E r was also confirmed quantitatively in the Hmode plasma at the initial ELMfree phase. When the inhomogeneity of radial electric field became strong enough, the inferred χ i,ped. value was close to its neoclassical one at the later ELMfree Hphase until 1st typeI ELM onset. Nevertheless, we observed the further reduction of electron density fluctuations (in the range up to 300 kHz) and D α signals in association with the increment of electric field inhomogeneity. These suggest that the electron turbulent transport is suppressed further.

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On the Origin of Steep and Localized Radial Electric Field in the Transport Barrier at Plasma Edge

Cited by 2 publications

References 52 publications

Experimental validation of non-uniformity effect of the radial electric field on the edge transport barrier formation in JT-60U H-mode plasmas

Experimental validation of non-uniformity effect of the radial electric field on the edge transport barrier formation in JT-60U H-mode plasmas

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

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