A First Study of Impurity Behavior During Externally Induced Radial Electric Fields in the TJ-II Stellarator

McCarthy, K. J.; Ochando, M. A.; Medina, F.; Zurro, B.; Hidalgo, C.; Pedrosa, Maria de los Angeles; Pastor, I.; Herranz, J.; Baciero, A.

doi:10.13182/fst04-a548

Cited by 6 publications

(4 citation statements)

References 10 publications

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“…the electron temperature remained constant. The results and analysis of the data collected provide, by their consistency, significant evidence that limiter biasing in the TJ-II does not induce significant influxes of impurities from the outer plasma region [32]. The phenomenology of TJ-II improved confinement regimes looks similar to the H-mode regimes previously reported in stellarators ( [18,33,34] and references therein).…”

Section: Biasing Induced Improved Confinement Regimessupporting

confidence: 75%

Overview of TJ-II experiments

Hidalgo¹,

Alejaldre²,

Alonso³

et al. 2005

Nucl. Fusion

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This paper presents an overview of experimental results and progress made in investigating the link between magnetic topology, electric fields and transport in the TJ-II stellarator. The smooth change from positive to negative electric field observed in the core region as the density is raised is correlated with global and local transport data. A statistical description of transport is emerging as a new way to describe the coupling between profiles, plasma flows and turbulence. TJ-II experiments show that the location of rational surfaces inside the plasma can, in some circumstances, provide a trigger for the development of core transitions, providing a critical test for the various models that have been proposed to explain the appearance of transport barriers in relation to magnetic topology. In the plasma core, perpendicular rotation is strongly coupled to plasma density, showing a reversal consistent with neoclassical expectations. In contrast, spontaneous sheared flows in the plasma edge appear to be coupled strongly to plasma turbulence, consistent with the expectation for turbulent driven flows. The local injection of hydrocarbons through a mobile limiter and the erosion produced by plasmas with well-known edge parameters opens the possibility of performing carbon transport studies, relevant for understanding co-deposit formation in fusion devices.

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Section: Biasing Induced Improved Confinement Regimessupporting

confidence: 75%

Overview of TJ-II experiments

Hidalgo¹,

Alejaldre²,

Alonso³

et al. 2005

Nucl. Fusion

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“…For the discharge under study, a neutrals density constant and equal to 10 10 cm −3 has been set to perform the calculations. The impurity density was fixed to n z = 0.1 n p , which is in good agreement with Z eff values [26]. The plasma main impurity which has been considered is carbon, according to the TJ-II spectra measurements in the VUV.…”

Section: Comparison Of the Model With Tj-ii Datamentioning

confidence: 73%

“…On the other hand, the higher proportion between suprathermal and bulk populations results in a higher bulk proton temperature. The behaviour with the impurities density, n z , has also been studied showing a very weak dependence for the rather small impurity concentrations observed at TJ-II (notice that Z eff values are smaller than 3 for the kind of discharges studied in this work [26]).…”

Section: Modellingmentioning

confidence: 80%

The role of a fast ion component on the heating of the plasma bulk

Rapisarda¹,

Zurro²,

Tribaldos³

et al. 2007

Plasma Phys. Control. Fusion

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Ion temperatures have been measured in the TJ-II stellarator using passive emission spectroscopy in parallel and perpendicular directions. A highenergy component was observed from the tails of the H α line emission in both directions, suggesting a non-negligible population of suprathermal ions. The role of this fast ion energy component, which has been observed in both stellarator and tokamak plasmas when heated by electron cyclotron resonance heating in the additional heating of the plasma bulk is investigated by means of a simple model. The origin of such a fast component is discussed in terms of different mechanisms.

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“…In any single shot, and with the 300 g/mm diffraction grating, a spectral band of 240 nm can be simultaneously recorded, hence only a modest number of reproducible plasma shots is needed to record a full range of ≈ 900 nm, covering from 750 to 1650 nm. Intrinsic impurities in TJ-II plasmas are He, Li, B, C, N, O, F, Fe and Cr [11]. As mentioned in the introduction, two types of plasmas can be obtained in the TJ-II device, depending on the heating methods used to maintain the plasma discharge, i.e., purely ECRH-heated plasmas, or plasmas that are created and initially sustained by ECRH-heating, but are subsequently sustained by Neutral Beam Injection (NBI) heating.…”

Section: Experimental Results and Preliminary Data Analysismentioning

confidence: 99%

Broad‐Band Time‐Resolved Near Infrared Spectroscopy in the TJ‐II Stellarator

Rodrı́guez

Pastor

Cal

et al. 2014

Contrib. Plasma Phys.

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First experimental results on broad‐band, time‐resolved Near Infrared (NIR;here loosely defined as covering from 750 to 1650 nm) passive spectroscopy using a high sensitivity InGaAs detector are reported for the TJ‐II Stellarator. Experimental set‐up is described together with its main characteristics, the most remarkable ones being its enhanced NIR response, broadband spectrum acquisition in a single shot, and time‐resolved measurements with up to 1.8 kHz spectral rate. Prospects for future work and more extended physics studies in this newly open spectral region in TJ‐II are discussed. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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A First Study of Impurity Behavior During Externally Induced Radial Electric Fields in the TJ-II Stellarator

Cited by 6 publications

References 10 publications

Overview of TJ-II experiments

Overview of TJ-II experiments

The role of a fast ion component on the heating of the plasma bulk

Broad‐Band Time‐Resolved Near Infrared Spectroscopy in the TJ‐II Stellarator

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