Impurity transport with strong and weak internal thermal barriers in JET optimized shear plasmas

Chen, H.; Hawkes, N.; Ingesson, L. C.; Peacock, N. J.; Haines, M. G.

doi:10.1088/0029-5515/41/1/303

Cited by 21 publications

(22 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observed peaking of light impurities is consistent with observations of ITBs on other devices [1,25]. When impurity profiles are compared with result of Chen [25], this Alcator C-Mod discharge appears to be similar to the strong ITB in JET. Strong and weak ITBs in JET are distinguished by the ITG, but the impurity profiles have a distinctive behaviour as well.…”

Section: Impurity Transportsupporting

confidence: 86%

Light impurity transport at an internal transport barrier in Alcator C-Mod

2008

View full text Add to dashboard Cite

Density profiles for a light impurity, boron, are reported for internal transport barrier (ITB) discharges in Alcator C-Mod. During the ITB, the light impurity gradient steepens because the impurity pinch increases relative to diffusion. The ITB-induced impurity profile steepening is at approximately the same major radius as that for the main-ion profile. Neoclassical transport does not describe the light impurity profiles but transport is closer to neoclassical in the ITB region. In previous work on C-Mod, profiles of seeded heavy impurities (introduced by puffing) peaked during the ITB, but a marked difference between transport of heavy and light impurities has been reported for other tokamaks. With the addition of light impurity profiles described here, the ITB on C-Mod is shown to share additional profile traits with the ITB on other tokamaks. This confirms that the macroscopic features of the C-Mod ITB are similar to those on other devices although it leaves open the details of the onset of the ITB.

show abstract

Section: Impurity Transportsupporting

confidence: 86%

Light impurity transport at an internal transport barrier in Alcator C-Mod

2008

View full text Add to dashboard Cite

show abstract

“…D, that as a result of the simulations can be taken practically independent of time, is mainly sensitive to the inflows of Ar (following the valve opening) and of C (following the application of NBI). Its profile has been found to decrease towards the plasma centre, but it has not been possible to prove the existence of an improved confinement core region, as reported in [6][7][8] in several JET experimental conditions. To obtain a better D(r) evaluation, Abel-inverted soft x-ray emissivity profiles are necessary (work is in progress in this direction).…”

Section: The Impurity Transport Modelmentioning

confidence: 83%

Radiation pattern and impurity transport in argon seeded ELMy H-mode discharges in JET

Puiatti

Mattioli

Telesca

et al. 2002

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

This paper addresses the issues of impurity behaviour during the argon seeding experiments in JET, in which argon and D 2 have been simultaneously puffed in ELMy H-mode discharges to reach high density regimes, maintaining good confinement properties throughout the plasma discharge. The analysis is based mainly on a 1-D impurity diffusion model, which evaluates the impurity transport coefficients in three experimental scenarios.The available experimental data include, as a function of the time, the brightnesses of the soft x-rays and of several impurity lines, the effective charge Z eff , the profiles of the radiated power and the fully stripped Ar and C ion densities from charge-exchange recombination. From the simulation of these data it is possible to characterize the considered scenarios in terms of high-Z ion increase in the plasma centre and high radiation from the edge. In particular, it has been found that the configuration at high triangularity with continuous D 2 puffing, characterized by an outward impurity pinch velocity, features flat or slightly hollow impurity ion profiles and high radiation from a narrow region at the edge, possibly associated to the presence of a significant neutral density. In this case an edge radiative mantle is established without high radiation from the plasma centre.

show abstract

“…It is also interesting that the observation of the impurity hole in LHD is in contrast to the impurity accumulation in ITBs in tokamaks, 29,30 where the temperature screening effect is canceled by the inward convection driven by the density gradient due to the improvement of particle transport. The experimental observation of the outward convection driven by the ITG should have a strong impact on the prospect of future research in nonaxisymmetric systems because it strongly supports the simultaneous achievement of good energy confinement and low impurity concentration, which is necessary for a fusion plasma.…”

Section: Discussionmentioning

confidence: 99%

Observation of an impurity hole in a plasma with an ion internal transport barrier in the Large Helical Device

et al. 2009

View full text Add to dashboard Cite

Extremely hollow profiles of impurities ͑denoted as "impurity hole"͒ are observed in the plasma with a steep gradient of the ion temperature after the formation of an internal transport barrier ͑ITB͒ in the ion temperature transport in the Large Helical Device ͓A. Iiyoshi et al., Nucl. Fusion 39, 1245 ͑1999͔͒. The radial profile of carbon becomes hollow during the ITB phase and the central carbon density keeps dropping and reaches 0.1%-0.3% of plasma density at the end of the ion ITB phase. The diffusion coefficient and the convective velocity of impurities are evaluated from the time evolution of carbon profiles assuming the diffusion and the convection velocity are constant in time after the formation of the ITB. The transport analysis gives a low diffusion of 0.1-0.2 m 2 / s and the outward convection velocity of ϳ1 m/ s at half of the minor radius, which is in contrast to the tendency in tokamak plasmas for the impurity density to increase due to an inward convection and low diffusion in the ITB region. The outward convection is considered to be driven by turbulence because the sign of the convection velocity contradicts the neoclassical theory where a negative electric field and an inward convection are predicted.

show abstract

Impurity transport with strong and weak internal thermal barriers in JET optimized shear plasmas

Cited by 21 publications

References 36 publications

Light impurity transport at an internal transport barrier in Alcator C-Mod

Light impurity transport at an internal transport barrier in Alcator C-Mod

Radiation pattern and impurity transport in argon seeded ELMy H-mode discharges in JET

Observation of an impurity hole in a plasma with an ion internal transport barrier in the Large Helical Device

Contact Info

Product

Resources

About