Toroidally symmetric/asymmetric effect on the divertor flux due to neon/nitrogen seeding in LHD

Tanaka, Hirohiko; Kawamura, G.; Masuzaki, S.; Kobayashi, M.; Akiyama, Tsuyoshi; Peterson, B.J.; Sano, Ryuichi; Dai, Shuyu; Sakamoto, R.; Morisaki, T.; Ohno, Noriyasu

doi:10.1016/j.nme.2016.12.020

Cited by 23 publications

(21 citation statements)

References 15 publications

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“…Only in the Large Helical Device (LHD) impurity seeding experiments were carried out. Here, Ne, N2 and Kr were used as most effective species and enhancement of plasma radiation as well as reduction of the divertor heat load were observed without significant confinement degradation [14] [15]. Ne was observed to radiate considerably from the confined region, although in its periphery, in addition to the strong edge radiation.…”

Section: Introductionmentioning

confidence: 99%

Radiative edge cooling experiments in Wendelstein 7-X start-up limiter campaign

et al. 2019

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Impurity seeding experiments during the start-up limiter campaign of Wendelstein 7-X provide first evidence for a localization effect of the three-dimensional magnetic edge structure on the seeded impurities and their radiation distribution and cooling effect. Moreover, species dependencies have been seen. Nitrogen was observed to cool the entire edge plasma, with a stronger electron temperature reduction measured at the downstream position at the limiter. The radiation was limited at the periphery of the confined region. Both the temperature reduction and the radiation enhancement were directly correlated to the injection of the coolant gas. Mitigation of the limiter heat loads was also measured. Neon was observed to affect also the confined plasma with a long-lasting radiation and a cooling of the entire plasma.

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Section: Introductionmentioning

confidence: 99%

Radiative edge cooling experiments in Wendelstein 7-X start-up limiter campaign

et al. 2019

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“…scitation.org/journal/rsi is divided into four radial regions, from radially outward to radially inward based on vacuum magnetic flux surfaces. The different imposed core radiation power densities and power density profiles in cases [2] and [3] are varied so as to include as many possibilities as possible in the calculation of the coefficients. In the flat power density profile case, the radiated power density itself is varied but is equal in each section of the core.…”

Section: Articlementioning

confidence: 99%

“…There is evidence that there are toroidal and poloidal radiation asymmetries in LHD discharges, especially after impurity gas seeding. 2,3 These radiation asymmetries can cause errors in the P rad prediction because they are distributed toroidally and poloidally over the plasma. Toroidal asymmetries occur in regions of the plasma that are not in the line of sight of the bolometer used for the measurement; using only one bolometer channel leads to a prediction error that is linearly related to the amplitude of the asymmetries.…”

Section: Introductionmentioning

confidence: 99%

Development of a weighted sum estimate of the total radiated power from large helical device plasma

Giessen

Kawamura

Borling

et al. 2021

Review of Scientific Instruments

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“…In the LHD, studies on the divertor detachment are performed by seeding impurities deliberately [17][18][19] and by applying RMP from special coils [20][21][22]. In this chapter, we focus on the detachment with the RMP application, which is a unique feature of the LHD.…”

Section: Experimental Observations On Detachment In the Heliotron Lhdmentioning

confidence: 99%

“…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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Toroidally symmetric/asymmetric effect on the divertor flux due to neon/nitrogen seeding in LHD

Cited by 23 publications

References 15 publications

Radiative edge cooling experiments in Wendelstein 7-X start-up limiter campaign

Radiative edge cooling experiments in Wendelstein 7-X start-up limiter campaign

Development of a weighted sum estimate of the total radiated power from large helical device plasma

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

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