Lithium sputtering from lithium-coated plasma facing components in the NSTX divertor

Scotti, F.; Soukhanovskii, V.; Ahn, J.-W.; Bell, R. E.; Gerhardt, S. P.; Jaworski, M. A.; Kaita, R.; Kugel, H.; McLean, A.G.; Meier, Eric; Podestà, M.; Roquemore, A. L.

doi:10.1016/j.jnucmat.2014.12.032

Cited by 17 publications

(5 citation statements)

References 20 publications

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“…The radial increase in density towards the strike point and the inverse dependence of the Li I photon emission coefficients on n e however could only account for a fraction of the decrease in fluctuations near the separatrix. This effect is also counteracted by the typical increase in lithium sputtering yield at the strike point in NSTX [39] which would instead act to increase the relative fluctuation level towards the strike point. Correlation analysis and comparison of correlations scale lengths were performed in the next sections to provide a better characterization of the disconnection in the proximity of the strike point.…”

Section: Divertor Turbulence Characteristicsmentioning

confidence: 99%

Disconnection of scrape off layer turbulence between the outer midplane and divertor target plate in NSTX

et al. 2019

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The connection between scrape off layer (SOL) turbulence at the outer midplane and at the divertor target plate is characterized in the National Spherical Torus Experiment (NSTX). Divertor fluctuations due to midplane blobs are studied by imaging their helical intersection with the divertor plate. Divertor fluctuation levels gradually decrease approaching the outer strike point. Divertor radial turbulence scale lengths as well as radial and poloidal turbulence propagation velocities are comparable to those on the low field side midplane. Strong correlation between divertor and midplane turbulence is observed in the far SOL. The correlation progressively decreases towards the separatrix, along with the decrease in the measured divertor fluctuations. The reduction in correlation is consistent with an electrostatic two-region blob model (Myra et al 2006 Phys. Plasmas 13 112502) with perpendicular ion polarization currents due to X-point geometry causing filament disconnection.

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Section: Divertor Turbulence Characteristicsmentioning

confidence: 99%

Disconnection of scrape off layer turbulence between the outer midplane and divertor target plate in NSTX

et al. 2019

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“…While carbon accumulation was observed in the plasma core, lithium densities remained below 1% of the carbon density. Lithium erosion at the divertor plate was found to be consistent with physical and temperature-enhanced erosion [157] while the application of lithium on graphite plasma facing components led to a moderate reduction in carbon sputtering. Toroidal asymmetries in divertor impurity influxes were found to be due to leading edges of divertor tiles (for carbon) and the toroidally asymmetric deposition from the lithium wall conditioning evaporators (for lithium) [158].…”

Section: Particle Transportmentioning

confidence: 66%

Thermal confinement and transport in spherical tokamaks: a review

Kaye¹,

Connor²,

Roach³

2021

Plasma Phys. Control. Fusion

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In this paper, we review the thermal plasma confinement and transport properties observed and predicted in low aspect ratio tokamaks, or spherical tokamaks (STs), which can depart significantly from those observed at higher aspect ratio. In particular, thermal energy confinement scalings show a strong, near linear dependence of energy confinement time on toroidal magnetic field, while the dependence on plasma current is more modest, the opposite of what is seen at higher aspect ratio. STs have revealed a very strong improvement in normalized confinement with decreasing collisionality, much stronger than at higher aspect ratio, which bodes well for an ST-based fusion pilot plant should this trend continue at an even lower collisionality than has already been accessed. These differences arise because of fundamental differences in transport in STs due to the more extreme toroidicity (i.e. reduced region of bad curvature), and to the relatively larger E r × B shearing rates, both of which can suppress electrostatic drift wave instabilities at both ion and electron gyroradius scales. In addition, electromagnetic effects are much stronger in STs because they operate at high β T . Gyrokinetic (GK) studies, coupled with low- and high-k turbulence measurements, have shed light on the underlying physics controlling transport. At lower β T , both ion- and electron-scale electrostatic drift turbulence may be responsible for transport. At higher βT , microtearing, kinetic ballooning, and hybrid trapped electron/kinetic ballooning modes increasingly play a role, and they have a much stronger impact in the core of ST plasmas than at higher aspect ratio. Flow shear affects the balance between ion- and electron-scale modes. Non-linear GK simulations find regimes where the electron heat flux decreases with decreasing collisionality, consistent with the experimental global normalized confinement scaling. The ST is unique in that the relatively low toroidal magnetic field allows for localized measurements of electron-scale turbulence, and this coupled with turbulence measurements at ion-scales has facilitated detailed comparisons with GK simulations. These data have provided compelling evidence for the presence of ion temperature gradient and electron temperature gradient turbulence in some plasmas, and direct experimental support for the impact of experimental actuators like rotation shear, density gradient and magnetic shear on turbulence and transport.

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“…Based on the results of earlier studies [1][2][3], lithium is the best for use as a structural material of the intrachamber devices of fusion reactor. The advantages of using lithium as PFM are confirmed by the results of studies conducted at plasma-physical installations of T11-M (Troitsk, Russia), FTU (Frascati, Italy), NSTX (Princeton, USA), EAST (Hefei, China), T-10 (Moscow, Russia), TJ-II (Barcelona, Spain), KTM (Kurchatov, Kazakhstan) [4][5][6][7][8][9][10][11]. In most cases, the realization of the advantage of lithium over conventional PFM is based on the use of the so-called lithium capillary-porous system (CPS), a fundamentally new material in which liquid lithium is stabilized in a matrix of solid porous material by capillary forces [12].…”

Section: Introductionmentioning

confidence: 69%

Methodology of the Experiments to Study Lithium CPS Interaction with Deuterium Under Conditions of Reactor Irradiation

Ponkratov

Nikitenkov

Tazhibayeva

et al. 2019

Eurasian Chem. Tech. J.

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Problems of plasma-facing materials degradation and in-vessel element destructions, tritium accumulation and plasma pollution can be overcome by the use of liquid metals with low atomic number. The best candidate as a material for divertor receiving plates and other in-vessel devices is lithium. One of the problems associated with the use of such lithium systems in the fusion reactors is to determine the parameters of the working gases interaction with plasma facing surfaces under conditions simulating real operation, i.e. under conditions of neutron and gamma radiation. This paper describes a technique of the reactor experiments to study lithium capillary-porous systems (CPS) interaction with deuterium under neutron irradiation. The neutron-physical and thermophysical calculations were the basis for the design development and further manufacture of a unique irradiation ampoule device with a lithium CPS sample. Several experiments were performed to calibrate the deuterium fluxes through experimental cell with lithium CPS; and preliminary results of these experiments were obtained.

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Lithium sputtering from lithium-coated plasma facing components in the NSTX divertor

Cited by 17 publications

References 20 publications

Disconnection of scrape off layer turbulence between the outer midplane and divertor target plate in NSTX

Disconnection of scrape off layer turbulence between the outer midplane and divertor target plate in NSTX

Thermal confinement and transport in spherical tokamaks: a review

Methodology of the Experiments to Study Lithium CPS Interaction with Deuterium Under Conditions of Reactor Irradiation

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