SOL plasma profiles under radiative and detached divertor conditions in JT-60U

Asakura, N.; Koide, Y.; Itami, K.; Hosogane, N.; Shimizu, K.; Tsuji‐Iio, S.; Sakurai, S.; Sakasai, A.

doi:10.1016/s0022-3115(97)80099-2

Cited by 51 publications

(41 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observation of the upstream density profiles further reveals the onset of a density shoulder during n e ramps in TCV, as discussed previously in [65,42,66,67], as well as on other devices such as Alcator C-Mod [68,69], Asdex-Upgrade [70,71], DIII-D [72], JET [73] and JT-60U [74]. This shoulder formation is apparent in the middle panel of figure 12, showing a distinct broadening of the upstream density profile when increasing density and moving from attached to detached conditions.…”

Section: Observation Of Density Shoulderssupporting

confidence: 77%

Nitrogen-seeded divertor detachment in TCV L-mode plasmas

Février

Theiler

Harrison

et al. 2020

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

Most of the detachment experiments done to date on the Tokamak a Configuration Variable (TCV), both in standard and alternative divertor geometries, focused on L-mode integrated core density ramps. In view of extending these studies to high-power, high-confinement regimes, where impurity seeding will be necessary for detachment, the properties of nitrogen seeded L-mode detachment in TCV are assessed here with the extensive set of edge and divertor diagnostics and similarities and differences with integrated core density (ne) ramp detachment experiments are elucidated. It is found that in high current, reversed field plasmas, detachment at the outer target is achieved with N 2-seeding and density ramps, with target heat flux reductions of up to 90%, while the inner target only detaches with seeding. The Scrape-Off Layer radiation fraction reaches values of 60-80% and in all situations, a stable radiator can form around the Xpoint. The most striking difference between seeding and density ramp is the behavior of the upstream quantities. During the ne-ramp, a broadening of the upstream density profile (density "shoulder") occurs, concurrent with the outer target ion flux roll-over, while no such behavior occurs during nitrogen seeded detachment. Separatrix density, electron temperature and pressure also evolve strongly with increasing density, and are largely unaffected by the injection of nitrogen. Comparison of upstream and target pressures reveals that, in all cases, the outer target ion flux reduction coincides with the development of a parallel gradient of the total pressure. Common to all cases is also a reduction of energy confinement time with detachment, although this effect is weak for seeding at relatively high density. Studying the impact of the ∇B-drift direction in both nitrogen seeding and core density ramps reveals that drifts mainly affect the behavior at the inner strike point, highlighting the need to include drift in edge transport simulations.

show abstract

Section: Observation Of Density Shoulderssupporting

confidence: 77%

Nitrogen-seeded divertor detachment in TCV L-mode plasmas

Février

Theiler

Harrison

et al. 2020

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…A ''shoulder'' in the cross-field density and temperature profiles have been seen in ASDEX 16 and JT-60U. 17 This feature is found to persist regardless of changes in the divertor geometry. 18,19 In ASDEX-UG, the profiles in the shoulder region could be reproduced in simulations by assuming a large outward drift of 70 m s Ϫ1 or an effective particle diffusion coefficient much larger than Bohm of D eff ϳ30 m 2 s Ϫ1 .…”

Section: Discussionmentioning

confidence: 88%

Particle transport in the scrape-off layer and its relationship to discharge density limit in Alcator C-Mod

LaBombard¹,

Boivin²,

Greenwald³

et al. 2001

Physics of Plasmas

236

303

View full text Add to dashboard Cite

Cross-field particle transport in the scrape-off layer ͑SOL͒ of Alcator C-Mod ͓Phys. Plasmas 1, 1511 ͑1994͔͒ can be characterized by an effective particle diffusivity (D eff) that increases markedly with distance from the separatrix. As a consequence, recycling onto the main-chamber walls is large compared to plasma flows into the divertor volume. The SOL exhibits a two-layer structure: Steep gradients and moderate fluctuation levels are typically found in a ϳ5 mm region near the separatrix ͑near SOL͒ where parallel electron conduction typically dominates energy losses. Small gradients and larger fluctuation levels with longer correlation times are found outside this region ͑far SOL͒. D eff in the near SOL increases strongly with local plasma collisionality normalized to the magnetic connection length. As the discharge density limit is approached, D eff and associated fluctuation levels become large across the entire SOL and cross-field heat convection everywhere exceeds parallel conduction losses, impacting the power balance of the discharge.

show abstract

“…The role of enhanced convective filamentary transport in the formation of SOL density shoulder has been already suggested [3,4,7,9], even though reduced parallel losses could also influence the process. The relation between profile evolution and blob-sizes has been investigated in the present scan using properly designed probes.…”

Section: Filamentary Studiesmentioning

confidence: 94%

“…Transport in the SOL region, resulting from a competition between sources and parallel and perpendicular losses, is dominated by the presence of intermittent structures or filaments, which strongly contribute to particle and eventually energy losses both in L-and H-mode regimes. The role of convective radial losses has become even more important due to its contribution to the process of profile broadening also known as shoulder formation in L-Mode, describing the progressive flattening of the density scrape off layer profile at high density [2,3,4,5,6,7,8,9] where future devices are expected to routinely operate. This increased radial transport could pose serious problems for Plasma Facing Components, enhanced by the recent observation that whenever flatter density profiles are established an increase of heat transport associated to filaments is observed in the far SOL, with filaments carrying up to 1/5 of the power ejected at the separatrix [10].…”

Section: Introductionmentioning

confidence: 99%

Scrape-off layer transport and filament characteristics in high-density tokamak regimes

et al. 2019

View full text Add to dashboard Cite

During the embargo period (the 12 month period from the publication of the Version of Record of this article), the Accepted Manuscript is fully protected by copyright and cannot be reused or reposted elsewhere. As the Version of Record of this article is going to be / has been published on a subscription basis, this Accepted Manuscript is available for reuse under a CC BY-NC-ND 3.0 licence after the 12 month embargo period.

show abstract

SOL plasma profiles under radiative and detached divertor conditions in JT-60U

Cited by 51 publications

References 7 publications

Nitrogen-seeded divertor detachment in TCV L-mode plasmas

Nitrogen-seeded divertor detachment in TCV L-mode plasmas

Particle transport in the scrape-off layer and its relationship to discharge density limit in Alcator C-Mod

Scrape-off layer transport and filament characteristics in high-density tokamak regimes

Contact Info

Product

Resources

About