Experimental verification of X-point potential well formation in unfavorable magnetic field direction

Wensing, M.; Oliveira, H. De; Loizu, Joaquim; Colandrea, C.; Février, O.; Gorno, S.; Reimerdes, H.; Theiler, C.; Smolders, A.; Duval, B.P.; Tsui, C.; Wischmeier, M.; Brida, D.; Henderson, S.; Komm, M.; Team, Tcv; Team, EUROfusion Mst

doi:10.1016/j.nme.2020.100839

Cited by 7 publications

(11 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The non-ambipolar contribution becomes however small towards high densities as the peak electric currents towards the target also is reduced. In the TCV divertor the parallel current is dominated by Pfirsch-Schlüter currents, as previously presented in 14 .…”

Section: Target Particle Fluxsupporting

confidence: 53%

“…These account for drifts, electric currents, carbon impurities and kinetic neutrals complementing previous simulations for TCV where drift effects were neglected 5,6 . Drift effects in TCV simulations were found to significantly affect cross-field transport, even in presence of anomalous transport 13 , and electric fields in dissipative divertor conditions 14 .…”

Section: B Solps Simulationsmentioning

confidence: 92%

See 1 more Smart Citation

SOLPS-ITER validation with TCV L-mode discharges

et al. 2021

Self Cite

View full text Add to dashboard Cite

This work presents a quantitative test of SOLPS-ITER simulations against TCV L-mode experiments. These simulations account for drifts, currents, kinetic neutrals and carbon impurities providing the most complete edge transport simulations for TCV to date. The comparison is performed on nominally identical discharges carried out to assess the effectiveness of TCV's divertor baffles in the framework of the European PEX program (Plasma EXhaust) and employs numerous edge diagnostics providing a detailed code-experiment benchmark for TCV. The simulations show qualitative consistency, but quantitative differences remain that are assessed herein. It is found that, for a given separatrix density, the simulations most notably yield a colder, and denser, divertor state with higher divertor neutral pressure than measured.

show abstract

Section: Target Particle Fluxsupporting

confidence: 53%

Section: B Solps Simulationsmentioning

confidence: 92%

SOLPS-ITER validation with TCV L-mode discharges

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…Notable feature of such situation is the appearance of potential well near the X-point, which can be registered experimentally. [38] It is important to mention that in the TCV reciprocating probe experiment [38] (reproduced by SOLPS-ITER modelling with full account of drifts and currents), the potential well was registered in high-density regime only, while with lower density potential was positive everywhere.…”

Section: Effects In Reversed B-fieldmentioning

confidence: 97%

“…Notable feature of such situation is the appearance of potential well near the X‐point, which can be registered experimentally. [ 38 ]…”

Section: Role Of Drifts and Currents In Divertor Plasmamentioning

confidence: 99%

See 1 more Smart Citation

Detached regime with highly radiating X‐point: Physics and modelling

Senichenkov

Rozhansky

Shtyrkhunov

et al. 2022

Contributions to Plasma Physics

View full text Add to dashboard Cite

A possibility to operate with fully detached targets and highly radiating X-point was recently demonstrated on ASDEX Upgrade, JET, and DIII-D with intensive impurity seeding (N, Ne, Ar) and feedback control. Notable feature of such a regime is the radiated power fraction of up to 90% of discharge power inside the separatrix without a confinement degradation, or even with confinement improvement (in terms of H-factor), which leads to a full detachment of both targets. Therefore, this regime might be attractive for the next generation reactor scale tokamaks like DEMO or CFETR, where most of the power should be radiated. In the present report, the recent achievements in the understanding of such regime are reviewed. The effectiveness of divertor target shielding by different impurity gases is discussed, paying attention to its first ionization potential. SOLPS-ITER modelling results illustrating the impurity flow pattern are presented, and the importance of drift flows is demonstrated. The effect of the machine size on the effectiveness of the divertor shielding by impurity radiation is discussed. It is demonstrated that in bigger machines impurity radiation is better kept in the divertor and divertor asymmetry is less pronounced. As the seeding rate increases, both targets fully detach, and neutrals start to penetrate inside the separatrix above the X-point, leading to the plasma cooling there and to the formation of an observable localized radiation spot in the X-point vicinity.The cold zone above the X-point thus behaves as an energy sink like a divertor in conventional regime, so that the perpendicular decay length of perpendicular turbulent energy flow appears to be of the order of 𝜆 q of conventional divertor.During the formation of the radiating X-point a potential hill/well (depending on the direction of B × ∇B drift) is formed on perturbed closed flux surfaces, and the corresponding E × B drift vortex fluxes appear to give major contribution to the particle balance. SOLPS-ITER simulations show that the radial electric field significantly deviates from neoclassical formula and may even change sign (become positive). Thus, the zone of maximal poloidal rotation shear may shift inwards, which might be responsible for the inward shift of the transport barrier and for the confinement improvement. This effect is different to the discussed extension of peeling-ballooning stability boundary by intensive impurity injection, which

show abstract

Numerical implications of including drifts in SOLPS-ITER simulations of EAST

Boeyaert,

Carli,

Dekeyser

et al. 2024

Physics of Plasmas

View full text Add to dashboard Cite

The inclusion of drifts in plasma edge codes like SOLPS-ITER is required to match simulation data with experimental profiles. However, this remains numerically challenging. In this paper, the effect of some numerical factors on the final plasma solution is investigated. This study is performed on three EAST simulations in the upper single null configuration: an attached purely deuterium case, an attached case with limited Ne-seeding, and a detached Ne-seeded case. The effects of the anomalous conductivity and anomalous thermo-electric coefficient on the plasma potential are investigated. Next, the effect of the employed grids is shown. In order to investigate these effects, accurate drift simulations are needed. Therefore, the employed time step and numerical parameters are discussed for the three studied simulations. For all presented simulations, it is verified that the restriction of the grid to the first flux surface tangent to the main chamber wall is sufficient within the context of non-extended simulations. This means that the main power dissipation takes place inside the simulated domain, and only a small fraction of the power is leaving the B2.5 grid through the grid boundary closest to the first wall. Finally, the effect of drifts on the asymmetry between the inner and outer target for EAST simulations is demonstrated.

show abstract

Experimental verification of X-point potential well formation in unfavorable magnetic field direction

Cited by 7 publications

References 12 publications

SOLPS-ITER validation with TCV L-mode discharges

SOLPS-ITER validation with TCV L-mode discharges

Detached regime with highly radiating X‐point: Physics and modelling

Numerical implications of including drifts in SOLPS-ITER simulations of EAST

Contact Info

Product

Resources

About