Effects of drifts on divertor plasma transport in LHD

Masuzaki, S.; Tanaka, Hirohiko; Kobayashi, M.; Kawamura, G.

doi:10.1016/j.nme.2019.01.009

Cited by 10 publications

(8 citation statements)

References 9 publications

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“…The divertor particle flux distributions are measured with Langmuir probes, which are installed at the divertor plates near midplane of 7 toroidal sections out of the total of 10 sections, as shown in Fig. 1 (a) [29,30]. Each toroidal section has two divertor arrays, which are named "Left (L)" and "Right (R)," as indicated in Fig.…”

Section: Effects Of Rmp On Toroidal Asymmetry Of Detachmentmentioning

confidence: 99%

“…Because of the n = 1 mode structure in the RMP, a toroidal asymmetry is induced for the divertor particle flux distribution, which can lead to toroidal asymmetry of detachment. The divertor particle flux distributions are measured with Langmuir probes, which are installed at the divertor plates near the midplane of 7 toroidal sections out of the total of 10 sections, as shown in figure 1(a) [29,30]. Each toroidal section has two divertor arrays, which are named 'Left (L)' and 'Right (R)', as indicated in figure 1(a).…”

Section: Effects Of Rmp On Toroidal Asymmetry Of Detachmentmentioning

confidence: 99%

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Impact of a resonant magnetic perturbation field on impurity radiation, divertor footprint, and core plasma transport in attached and detached plasmas in the Large Helical Device

et al. 2019

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Effects of resonant magnetic perturbation (RMP) field on impurity radiation, divertor footprint distribution, and core plasma transport are investigated in the detachment discharges of LHD. The RMP with m/n = 1/1 mode creates edge magnetic island in the stochastic layer, which enhances the impurity emission from low charge states, C 2+ and C 3+ , and then triggers detachment transition. The emission from the higher charge states, C 4+ and C 5+ , implies enhanced penetration of impurity during detachment phase with RMP. The toroidal divertor particle flux distribution exhibits n = 1 mode structure in both attached and detached phases, but with a large toroidal phase shift between the two phases. The distribution in the attached phase is well correlated with magnetic footprint of field line connection length calculated by the vacuum approximation. During the detached phase, however, the phase shift is not well explained by the vacuum approximation, where significant plasma response to the external RMP is observed. The energy confinement time becomes systematically shorter with RMP application due to the shrinkage of plasma volume caused by the edge magnetic island. On the other hand, the pressure profile during detachment with RMP is found to be more peaked than without RMP. The analysis with the core transport code TASK3D, taking into account heating profiles of NBI, shows no significant transport degradation during detachment with RMP application, whilst the enhanced radiation, the reduced divertor flux, and the possible impurity penetration.

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Section: Effects Of Rmp On Toroidal Asymmetry Of Detachmentmentioning

confidence: 99%

Section: Effects Of Rmp On Toroidal Asymmetry Of Detachmentmentioning

confidence: 99%

Impact of a resonant magnetic perturbation field on impurity radiation, divertor footprint, and core plasma transport in attached and detached plasmas in the Large Helical Device

et al. 2019

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“…These up-down asymmetries in B deposition are considered mainly to be caused by the edge particle drift. Although, the upper and lower divertor targets are identical in their geometry and in the topology of magnetic field, movements of charged particles can be drifted by magnetic field (B), electrical fields (E), the curvature, and gradients of magnetic field strength [21][22][23]. In W7-X, the intersection of scrapper-off layer (SOL) flux tubes and divertor target forms the SOL region on divertor target.…”

Section: Discussionmentioning

confidence: 99%

Distributions of deposits and hydrogen on the upper and lower TDUs3 target elements of Wendelstein 7-X

Zhao¹,

Masuzaki²,

Motojima³

et al. 2022

Nucl. Fusion

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Distributions of deposits and hydrogen (H) on the graphite divertor target elements TM4h4 and TM3v5 in the test divertor units 3 (TDUs3) of Wendelstein 7-X (W7-X) are studied. The TM4h4 and TM3v5 are located at the magnetically symmetric positions in the upper and lower divertor. The microstructure of the deposition layer is characterized by a transmission electron microscope (TEM) combined with a focused ion beam (FIB). Metallic deposits such as iron (Fe), molybdenum (Mo), chromium (Cr) are detected in the deposition layer by energy-dispersive X-ray spectroscopy (EDS). The depth-resolved distribution patterns of boron (B) and metallic deposits on upper and lower horizontal (h) divertor target elements TM4h4 as well as upper and lower vertical (v) divertor target elements TM3v5 are clarified by glow discharge optical emission spectrometry (GDOES). Results for both TM4h4 and TM3v5 show that the B deposition regions exhibit higher H retention due to the co-deposition with deposits. On the other hand, up-down asymmetries in B deposition caused by particle drift exist on both TM4h4 and TM3v5. The B deposition amount on upper TM4h4 is 40% smaller than that on lower TM4h4. While for the vertical target elements, the B deposition amount on upper TM3v5 is 35% larger than that on lower TM3v5. Meanwhile, a shift of around 3 cm in B deposition peaks is observed on upper and lower TM4h4 and TM3v5. Results of numerical simulation of carbon deposition/erosion profiles on the target elements using ERO2.0 code and power flux measured by infrared cameras are shown and compared with the above mentioned B profiles.

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“…The toroidal variation of the particle fluxes onto divertor plates with RMP has been investigated with Langmuir probe array installed around the mid-plane of the targets at the inboard side [17,31]. It has been found that the time evolution of the divertor particle flux exhibits substantial difference between toroidal locations, that is, some plates are becoming detached earlier than others; at some plates, the flux even increases after detachment [27].…”

Section: Change Of Divertor Footprint With Rmp Applicationmentioning

confidence: 99%

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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Effects of drifts on divertor plasma transport in LHD

Cited by 10 publications

References 9 publications

Impact of a resonant magnetic perturbation field on impurity radiation, divertor footprint, and core plasma transport in attached and detached plasmas in the Large Helical Device

Impact of a resonant magnetic perturbation field on impurity radiation, divertor footprint, and core plasma transport in attached and detached plasmas in the Large Helical Device

Distributions of deposits and hydrogen on the upper and lower TDUs3 target elements of Wendelstein 7-X

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

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