Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements

Langenberg, Andreas; Warmer, F.; Fuchert, G.; Marchuk, O.; Dinklage, A.; Wegner, Th; Alonso, J. A.; Bozhenkov, S.; Brunner, K. J.; Burhenn, R.; Buttenschön, B.; Drews, P.; Geiger, B.; Grulke, O.; Hirsch, M.; Höfel, U.; Hollfeld, K. P.; Killer, C.; Knauer, J.; Krings, T.; Kunkel, F.; Neuner, U.; Offermanns, G.; Pablant, N. A.; Pasch, E.; Rahbarnia, K.; Satheeswaran, G.; Schilling, J.; Schweer, B.; Thomsen, H.; Traverso, P.; Wolf, R. C.

doi:10.1088/1361-6587/aaeb74

Title: Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements

Journal Article · Fri Nov 23 00:00:00 EST 2018 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/aaeb74· OSTI ID:1485104

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^[1]; Fuchert, G. ^[1];

^[2]; Dinklage, A. ^[1];

^[1]; Alonso, J. A. ^[3];

^[1]; Brunner, K. J. ^[1]; Burhenn, R. ^[1];

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^[2]; Geiger, B. ^[1]; Grulke, O. ^[4]; Hirsch, M. ^[1]; Höfel, U. ^[1]; Hollfeld, K. P. ^[2];

^[1]; Knauer, J. ^[1]; Krings, T. ^[2] more »

Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany)
Forschungszentrum Julich GmbH, Julich (Germany)
Lab. Nacional de Fusion, Madrid (Spain)
Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany); Technical Univ. of Denmark DTU, Lyngby (Denmark)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Auburn Univ., Auburn, AL (United States)

This study reports on the effect of on- and off-axis heating power deposition on the impurity confinement in purely electron cyclotron resonance heated He plasmas on the stellarator Wendelstein 7-X. Therefore, impurity transport times τ _I have been determined after Fe impurity injections by laser ablations and monitoring the temporal impurity emissivities by the x-ray imaging spectrometer HR-XIS. A significant increase of τ _I has been observed when changing the power deposition from on- to off-axis heating with energy confinement times τ _E being mainly unaffected. In addition, the scaling of impurity transport properties with respect to a variation of heating power P _ECRH and electron density n _e has been investigated by keeping the heating power deposition on-axis. The observed τ _I scaling compares well to known τ _I scaling laws observed in other machines. A comparison of τ _I and τ _E yields an averaged ratio of τ _E /τ _I = 1.3 and transport times in the range of τ _I = 40–130 ms and τ _E = 40–190 ms. Comparing those absolute values to neoclassical predictions supports the recently observed nature of anomalous transport in Wendelstein 7-X, given within the up to now investigated operational parameters.

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Research Organization:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: the W7-X Team

Grant/Contract Number:: No 633053

OSTI ID:: 1485104

Journal Information:: Plasma Physics and Controlled Fusion, Vol. 61, Issue 1; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 7 works

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