Characterization of neutral loop discharges in the VINETA device

Stechow, A. von; Grulke, O.; Klinger, T.

doi:10.1140/epjd/e2012-20542-6

Cited by 2 publications

(1 citation statement)

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“…It consists of a phase after the injection of pellets during ECRH operation in which record values of T i,core 2.5 keV and stored energy, W dia 1 MJ are achieved while core transport is substantially reduced, matching neoclassical levels [14]. Consistently, a substantial reduction of turbulence amplitude is observed experimentally during this phase [15,16]. Besides HP operation, similar transitory phases also featuring enhanced density gradients and reduced turbulence have been observed in W7-X following the injection of impurities [17].…”

Section: Introductionmentioning

confidence: 63%

An experimental characterization of core turbulence regimes in Wendelstein 7-X

Carralero,

Estrada,

Maragkoudakis

et al. 2021

Preprint

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First results from the optimized helias Wendelstein 7-X stellarator (W7-X) have shown that core transport is no longer mostly neoclassical, as is the case in previous kinds of stellarators. Instead, power balance analysis has shown that turbulent transport poses a serious limitation to the global performance of the machine. Several studies have found this particularly relevant for ion transport, with core ion temperatures becoming clamped at relatively low values of T i 1.7 keV, except in the few scenarios in which turbulence can be suppressed. In order to understand the precise turbulent mechanisms at play and thus design improved performance scenarios, it is important to have a clear understanding of the parametric dependencies of turbulent fluctuations, and the relation between them and turbulent transport. As a first step in this direction, in this work we use Doppler reflectometry measurements carried out during a number of relevant operational scenarios to provide a systematic characterization of ionscale (k ⊥ ρ i 1) density fluctuations in the core of W7-X. Then, we study the relation between fluctuation amplitude and plasma profiles and show how distinct regimes can be defined for the former, depending on normalized gradients

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Section: Introductionmentioning

confidence: 63%