Investigation of ion and electron heat transport of high-<i>T</i><sub>e</sub>ECH heated discharges in the large helical device

Pablant, N.; Satake, S.; Yokoyama, M.; Gates, D.; Bitter, M.; Bertelli, N.; Delgado‐Aparicio, L.; Dinklage, A.; Goto, M.; Hill, K. W.; Igamai, S; Kubo, S.; Lazerson, S.; Matsuoka, Seikichi; Mikkelsen, D. R.; Morita, S.; Oishi, Tetsutarou; Seki, R.; Shimozuma, Τ.; Suzuki, C.; Suzuki, Yasuhiro; Takahashi, H.; Yamada, H.; Yoshimura, Y.

doi:10.1088/0741-3335/58/4/045004

Cited by 8 publications

(8 citation statements)

References 31 publications

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“…The electron heat diffusivity is also at the ion neoclassical heat diffusion level, but remains significantly above the electron neoclassical heat diffusivity, consistent with observations at JT-60U [10]. Similarly, a transport analysis of a high-T e electron cyclotron heated plasma in LHD showed that while the measured electron heat flux exceeds the neoclassical values by an order of magnitude, the measured ion heat flux is comparable to the neoclassical prediction [11].…”

Section: Nuclear Fusionsupporting

confidence: 83%

Ion heat transport dynamics during edge localized mode cycles at ASDEX Upgrade

et al. 2018

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The edge ion heat transport is analyzed in ASDEX Upgrade (AUG) by combining a comprehensive set of pedestal measurements with both interpretive and predictive modelling. The experimentally determined ion heat diffusivities, χ i , are compared with neoclassical theory and the impact of edge localized modes (ELMs) on the edge ion heat transport level is studied in detail. Pedestal matching experiments in deuterium and hydrogen plasmas show that the inter-ELM pedestal χ i remains close to the neoclassical value. The additional power needed in hydrogen to get similar pedestal temperatures as in deuterium plasmas mostly affects the electron heat channel, i.e. the electron heat diffusivity increases while the ion heat diffusivity stays at the same level within the uncertainties. Sub-ms measurements of the edge ion temperature allows us to extend the analysis to the entire ELM cycle. During the ELM crash, the ion heat transport is increased by an order of magnitude. The perturbed heat flux increases first at the separatrix, i.e. first the separatrix ion temperature increases, leading to a flatter ion temperature gradient, followed by a decrease of the whole pedestal profile. The ion heat transport returns to its pre-ELM neoclassical level 3-4 ms after the ELM crash.

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Section: Nuclear Fusionsupporting

confidence: 83%

Ion heat transport dynamics during edge localized mode cycles at ASDEX Upgrade

et al. 2018

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“…Using standard Doppler spectroscopy techniques, this diagnostic can provide line-integrated profiles of the ion-temperature (T i ) from line broadening, electron temperature (T e ) from line ratios, perpendicular flow velocity (u ⊥ ) from line shifts and impurity concentration from the line brightness. Tomographic inversion, using a known plasma equilibrium is used to infer the local plasma parameters from the line integrated data 8,9 . A description of the XICS system on W7-X can be found in Ref.…”

Section: Diagnostic Methodsmentioning

confidence: 99%

Core radial electric field and transport in Wendelstein 7-X plasmas

Pablant

Langenberg

Alonso³

et al. 2018

Physics of Plasmas

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Results from the investigation of neoclassical core transport and the role of the radial electric field profile (E r) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the E r profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u ⊥) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer (XICS) and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of ∆u ⊥ ∼ 5 km/s (∆E r ∼ 12 kV /m), have been observed within a set of experiments where the heating power was stepped down from 2 M W to 0.6 M W. These experiments are examined in detail to explore the relationship between heating power, temperature and density profiles and the radial electric field. Finally the inferred E r profiles are compared to initial neoclassical calculations using measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d and dkes, are compared both with each other and the measurements. These comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.

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“…Radial electric fields and the comparison between NC theory and experiments have been studied on other many other stellarator devices [9,10] including LHD [11,12], W7-AS [13,14], TJ-II [15], HSX [16,17], CHS [18,19] and Heliotron-J [20]. The experimental uncertainties and level of quantitative agreement varies between these studies, however overall they all point towards the validity of neoclassical theory in describing the ambipolar radial electric field.…”

Section: Introductionmentioning

confidence: 99%