First divertor physics studies in Wendelstein 7-X

Pedersen, T. S.; König, R.; Jakubowski, M.; Krychowiak, M.; Gradic, D.; Killer, C.; Niemann, H.; Szepesi, T.; Wenzel, U.; Ali, Adnan; Anda, G.; Baldzuhn, J.; Barbui, T.; Biedermann, C.; Blackwell, B. D.; Bosch, H.‐S.; Bozhenkov, S.; Brakel, R.; Brezinsek, S.; Cai, Jianqing; Cannas, B.; Coenen, J. W.; Cosfeld, J.; Dinklage, A.; Dittmar, T.; Drewelow, P.; Drews, P.; Dunai, D.; Effenberg, F.; Endler, M.; Feng, Y.; Fellinger, J.; Ford, O.; Frerichs, H.; Fuchert, G.; Gao, Yu; Geiger, J.; Goriaev, A.; Hammond, K. C.; Harris, J. H.; Hathiramani, D.; Henkel, Malte; Kazakov, Ye. O.; Kirschner, A.; Knieps, A.; Kobayashi, M.; Kocsis, G.; Kornejew, P.; Kremeyer, T.; Lazerzon, S.; LeViness, Alexandra; Li, C.; Li, Y.; Liang, Yun-Feng; Liu, Shaocheng; Lore, J.; Masuzaki, S.; Moncada, V.; Neubauer, O.; Ngo, T.; Oelmann, J.; Otte, M.; Perseo, V.; Pisano, F.; Sitjes, A. Puig; Rack, M.; Rasiński, M.; Romazanov, J.; Rudischhauser, L.; Schlisio, G.; Schmitt, J. C.; Schmitz, O.; Schweer, B.; Sereda, S.; Ślęczka, M.; Suzuki, Y.; Vécsei, M.; Wang, E.; Wauters, T.; Wiesen, S.; Winters, V.; Wurden, G. A.; Zhang, D.; Zoletnik, S.

doi:10.1088/1741-4326/ab280f

Cited by 48 publications

(57 citation statements)

References 29 publications

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“…Similar observations of the detached plasma stabilization with large island were also found in W7-AS [29]. The recent results on the successful detachment control in W7-X with the island divertor also suggest an important role of the edge magnetic island for the detached plasma stability [30].…”

Section: Rmp Impact On the Edge Impurity Radiation And Stability Of Dsupporting

confidence: 78%

Experimental Studies of and Theoretical Models for Detachment in Helical Fusion Devices

Kobayashi¹,

Tokar²

2020

Fusion Energy

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Good plasma performance in magnetic fusion devices of different types, both tokamaks and helical devices, is achieved normally if the plasma density does not exceed a certain limit. In devices with a divertor, such as tokamaks JET, JT-60U, and heliotron large helical device (LHD), by approaching the density limit, the plasma detaches from the divertor target plates so that the particle and heat fluxes onto the targets reduce dramatically. This is an attractive scenario for fusion reactors, offering a solution to the plasma-wall interaction problem. However, the main concerns by realizing such a scenario are the stability of the detached zone. The activity on the heliotron LHD aimed on detachment stabilization, by applying a resonant magnetic perturbation (RMP) and generating a wide magnetic island at the plasma edge, will be reviewed. Also, theoretical models, explaining the detachment conditions, low-frequency oscillations at the detachment onset, and mechanisms of the detached plasma stabilization by RMP, will be discussed.

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Section: Rmp Impact On the Edge Impurity Radiation And Stability Of Dsupporting

confidence: 78%

Experimental Studies of and Theoretical Models for Detachment in Helical Fusion Devices

Kobayashi¹,

Tokar²

2020

Fusion Energy

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“…The mentioned island-divertor concept used in W7-X was tested for the first time in the predecessor experiment W7-AS [7]. In W7-X, the island divertor proved to be quite successful with respect to the particle and energy exhaust and even a stable power and particle detachment could be shown in OP 1.2 [8,4]. According to periodicity and stellarator-symmetry (a flip-symmetry in one period) ten divertor units are distributed toroidally with five in the upper (labelled as 1-5u) and five in the lower part (1-5l) of the machine [9, Figure 1 therein].…”

Section: Introductionmentioning

confidence: 99%

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X

et al. 2020

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The operational regimes in the first divertor campaign of W7-X were limited by unexpectedly high heat loads on certain baffle tiles. In the high-mirror configuration, a permanent hotspot on the baffle plate was detected by the thermographic system, which was further confirmed during the post-campaign inspections of the plasmafacing components. The maximum heat load on three baffle tiles reached about 4.5 MW m −2 , which was almost an order of magnitude above its designed value of 0.5 MW m −2 . The paper presents a detailed analysis to understand how the baffle plate, which is originally designed to screen the recycling neutrals and is therefore hidden from the hot plasma, can receive such a high heat load -a level that is expected for target plates. Three main causes have been identified: 1) the three baffle tiles are radially only about 5 mm away from a main heat channel towards a target, which is much shorter than the radial power decay length of several centimeters derived from the thermographic measurements in this region; 2) the three baffle tiles are intersected with field-lines of about 30 m length, which are long enough to collect considerable amount of heat via cross-field transport; 3) the baffle tiles have locally large grazing angles. In addition, the analysis method shown in this paper is of general use to estimate the heat flows in shadow areas of targets and thus to evaluate heat loads on the potentially critical components occurring in these areas, especially required for the design of complex 3D divertors like the one in W7-X.

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“…The world biggest stellarator Wendelstein 7-X (W7-X) will resume operation in the next few years (Klinger et al 2019;Pedersen et al 2019). The ion-cyclotron plasma heating (ICRH) system will be installed at it among other new equipment.…”

Section: Introductionmentioning

confidence: 99%

First experiments on ICRF discharge generation by a W7-X-like antenna in the Uragan-2M stellarator

Moiseenko

Kovtun

Wauters³

et al. 2020

J. Plasma Phys.

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In support of the ICRF experiments planned on the Wendelstein 7-X (W7-X) stellarator, i.e. fast ion generation, wall conditioning, target plasma production and heating, a first experimental study on plasma production has been made in the Uragan-2M (U-2M) stellarator using W7-X-like two-strap antenna. In all the experiments, antenna monopole phasing was used. The W7-X-like antenna operation with launched radiofrequency power of ~100 kW have been performed in helium (p = (4–14) × 10−2 Pa) with the vacuum vessel walls pre-loaded with hydrogen. Production of plasma with a density higher than 1012 cm−3 was observed near the first harmonic of the hydrogen cyclotron frequency. Operation at first hydrogen harmonic is feasible in W7-X future ICRF experiments.

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First divertor physics studies in Wendelstein 7-X

Cited by 48 publications

References 29 publications

Experimental Studies of and Theoretical Models for Detachment in Helical Fusion Devices

Experimental Studies of and Theoretical Models for Detachment in Helical Fusion Devices

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X

First experiments on ICRF discharge generation by a W7-X-like antenna in the Uragan-2M stellarator

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