Divertor tungsten tile melting and its effect on core plasma performance

Lipschultz, B.; Coenen, J. W.; Barnard, Harold; Howard, N. T.; Reinke, M.L.; Whyte, D.G.; Wright, G.M.

doi:10.1088/0029-5515/52/12/123002

Cited by 63 publications

(53 citation statements)

References 34 publications

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“…iv) in comparison to carbon equivalent discharges, total radiation is similar but the edge radiation is lower and Z eff of the order of 1.3-1. 4. At low gas fuelling rate (below 0.5 10 22 D/s) and low ELM frequency (typically less than 10Hz), strong core radiation peaking is observed in H-mode discharges even when tungsten influx from the divertor is constant.…”

Section: Introductionmentioning

confidence: 95%

First scenario development with the JET new ITER-like wall

Joffrin

Baruzzo²,

Beurskens

et al. 2013

Nucl. Fusion

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In the recent JET experimental campaigns with the new ITER-like wall (JET-ILW), major progress has been achieved in the characterization and operation of the H-mode regime in metallic environments: (i) plasma breakdown has been achieved at the first attempt and X-point L-mode operation recovered in a few days of operation; (ii) stationary and stable type-I ELMy H-modes with βN ∼ 1.4 have been achieved in low and high triangularity ITER-like shape plasmas and are showing that their operational domain at H = 1 is significantly reduced with the JET-ILW mainly because of the need to inject a large amount of gas (above 1022 D s−1) to control core radiation; (iii) in contrast, the hybrid H-mode scenario has reached an H factor of 1.2–1.3 at βN of 3 for 2–3 s; and, (iv) in comparison to carbon equivalent discharges, total radiation is similar but the edge radiation is lower and Zeff of the order of 1.3–1.4. Strong core radiation peaking is observed in H-mode discharges at a low gas fuelling rate (i.e. below 0.5 × 1022 D s−1) and low ELM frequency (typically less than 10 Hz), even when the tungsten influx from the diverter is constant. High-Z impurity transport from the plasma edge to the core appears to be the dominant factor to explain these observations. This paper reviews the major physics and operational achievements and challenges that an ITER-like wall configuration has to face to produce stable plasma scenarios with maximized performance.

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Section: Introductionmentioning

confidence: 95%

First scenario development with the JET new ITER-like wall

Joffrin

Baruzzo²,

Beurskens

et al. 2013

Nucl. Fusion

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“…The latter will depend on the plasma conditions in front of the plasma-facing surface, which for the ITER divertor cannot be matched in existing tokamaks. The condequences of melting and droplet ejection from molten surfaces have been observed, for example, in Alcator C-Mod, where H-mode operation was impossible [13]. Similarly, a strong increase in the radiated power could be correlated with the penetration of large tungsten droplets in the plasma core of TEXTOR [6].…”

Section: Introductionmentioning

confidence: 99%

Melt-layer motion and droplet ejection under divertor-relevant plasma conditions

Temmerman¹,

Daniëls²,

Bystrov

et al. 2013

Nucl. Fusion

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Accidental melting of metallic plasma-facing materials in future fusion devices poses serious issues regarding the material lifetime and power-handling capabilities as well as core plasma performances. The behaviour of aluminum (as a proxy for beryllium) and tungsten materials has been investigated in the Pilot-PSI linear plasma device to study the melt layer motion and droplet ejection under ITER-relevant plasma conditions. Heat fluxes of up to 50 MW·m −2 raised the surface temperature to values up to 5000 K. The melt layer rotation was found to depend on the magnetic field (up to 1.6 T) strength and target potential and is attributed to J × B forces caused by radial currents in the plasma. The amount of droplets ejected from the molten surface depends on the material-more droplets ejected from aluminum than from tungstenand the heat flux to the target. The average droplet velocity was determined to be around 60 m·s −1 for both materials with droplets being ejected mainly in the axial direction. Droplet ejection is only observed during helium discharges, no ejection can be observed with hydrogen plasmas despite similar heat fluxes. Bubble boiling appears to be the main mechanism contributing to the observed droplet ejection.

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“…They are heavily bombarded by energetic particles during plasma shots. Consequently, the temperature of the leading edge could reach the melting point of tungsten, resulting in the movement of molten tungsten in the direction of j × B [17][18][19]. By tilting and shaping of the castellated structure, and by changing its angle with respect to the field line, leading edges can be hidden from the plasma particles.…”

Section: Damage and Melting Test Of Tungsten Blocks By Power Loading mentioning

confidence: 99%

“…It was also found that the molten droplets of W were directed towards the high field side due to j × B force as reported in Refs. [17][18][19].…”

Section: Damage and Melting Test Of Tungsten Blocks By Power Loading mentioning

confidence: 99%

A brief summary of tungsten technology development in Korea

Hong

2020

Tungsten

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A review of tungsten technology development in Korea is briefly given. According to the upgrade plan of Korea superconducting tokamak advanced research (KSTAR) tokamak associated with Korean fusion energy R&D program, graphite plasma-facing components will be replaced with tungsten-based ones to handle the high-peak heat load caused by an increase of heating power up to 26 MW. Brazing technique to bond tungsten was developed and tungsten blocks were manufactured. Blocks were installed at the central divertor in KSTAR and exposed to high heat flux. Under high heat flux and long-pulse discharge, tungsten blocks were severely damaged. Molten tungsten materials show movements towards the high field side, which is j×B direction. The COMSOL ® modeling described the melting event quantitatively well. The failure of a water cooling system with a metal wall environment during a long-pulse plasma operation is very critical.

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Divertor tungsten tile melting and its effect on core plasma performance

Cited by 63 publications

References 34 publications

First scenario development with the JET new ITER-like wall

First scenario development with the JET new ITER-like wall

Melt-layer motion and droplet ejection under divertor-relevant plasma conditions

A brief summary of tungsten technology development in Korea

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