Tungsten melt layer erosion due to J×B force under conditions relevant to ITER ELMs

Garkusha, I.E.; Базылев, Б.; Bandura, A. N.; Byrka, O.V.; Chebotarev, V. V.; Landman, I.; Kulik, N.V.; Makhlaj, V.A.; Petrov, Yu. V.; Solyakov, D. G.; Tereshin, V.I.

doi:10.1016/j.jnucmat.2007.01.168

Cited by 30 publications

(26 citation statements)

References 6 publications

(10 reference statements)

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“…Meltlayer motion as observed in the Quasi Stationary Plasma Accelerator (QSPA) facilities [3,4,5,6] is driven by the high plasma pressure (∼ 10 5 Pa). Few studies have in addition considered Lorentz-forces (F j×B ) due to thermoelectric emission and those have been done at medium B-fields (1.4T ) [17]. The driving force which has been identified as cause for bridging the castellation is the inertia of the melt at the gap edge competing with the surface tension, melt layer splashing is assumed to be caused due to high velocity shears leading to Kelvin-Helmholtz instabilities [5,4].…”

Section: Results and Measurementsmentioning

confidence: 99%

Analysis of tungsten melt-layer motion and splashing under tokamak conditions at TEXTOR

et al. 2011

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Behavior and characteristics of tungsten under impinging high heat-fluxes are investigated in view of the material choices for future devices such as ITER and DEMO. Experiments have been performed in the edge of the TEXTOR tokamak to study melt-layer motion, macroscopic melt layer erosion as well as the changes of the material properties. The parallel heat-flux ranges around q ∼ 45M W/m 2 allowing samples at an impact angle of 35 • to be exposed to 20 − 30M W/m 2 . Melt-layer motion perpendicular to the magnetic field is observed following a Lorentzforce originating from thermoelectric emission of the hot sample. Up to 3 g of tungsten are redistributed forming mountain like structures at the edge of the sample. The typical melt layer thickness is 1 − 1.5mm. Those hills are particularly susceptible to even higher heat-fluxes of up to the full q . Locally the temperature can reach up to 6000K, high levels of evaporation are causing significant erosion in form of continuous fine-spray (∼ 1 · 10 24 atoms m −2 s −1 ). Vaporshielding is occurring and hindering the further heating of the samples. In addition the formation of ligaments and splashes occurs several times during the melt phase ejecting droplets in the order of several 10µm up to 100µm probably caused by a Kelvin-Helmholtz instability evolving in the melt. In terms of material degradation several aspects are considered: formation of leading edges by redistributed melt, bubble formation and re-crystallization. Bubbles are occurring in sizes between µm and 200 µm while recrystallization increases the grain size up to 1.5 mm. The power handling capabilities are thus severely degraded. Melting of Tungsten in future devices is highly unfavorable and needs to be avoided especially in light of uncontrolled transients and possible unshaped PFCs

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Section: Results and Measurementsmentioning

confidence: 99%

Analysis of tungsten melt-layer motion and splashing under tokamak conditions at TEXTOR

et al. 2011

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“…The samples have been exposed to hydrogen plasma streams produced by the quasi-steady-state plasma accelerator QSPA Kh-50, described elsewhere [6][7][8]. Scheme of plasma exposures is presented in Fig.…”

Section: Methodsmentioning

confidence: 99%

Experimental study of plasma energy transfer and material erosion under ELM-like heat loads

Garkusha

Makhlaj

Chebotarev

et al. 2009

Journal of Nuclear Materials

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“…measure the thermo-electric emission [17,23,24] causing melt layer motion in fusion devices [3,4,25,26,27,28].…”

Section: Introductionmentioning

confidence: 99%

Transient induced tungsten melting at the Joint European Torus (JET)

et al. 2017

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Melting is one of the major risks associated with Tungsten Plasma-Facing Components (PFCs) in tokamaks like JET or ITER. These Components are designed such that leading edges and hence excessive plasma heat loads deposited at near normal incidence are avoided. Due to the high stored energies in ITER discharges, shallow surface melting can occur under insufficiently mitigated plasma disruption and so called Edge Localised Modes -Power load transients.A dedicated program was carried out at the Joint European Torus (JET) to study the physics and consequences of W transient melting. Following initial exposures in 2013 (ILW-1) of a Tungsten-lamella with leading edge, new experiments have been performed on a sloped surface (15 • slope) during the 2015/2016 (ILW-3) campaign. This new experiment allows significantly improved Infrared thermography measurements and thus resolved important issue of power loading in the context of the previous leading edge exposures. The new lamella was monitored by local diagnostics: spectroscopy, thermography and high resolution photography in between discharges. No impact on the main plasma was observed despite a strong increase of the local W source consistent with evaporation. In contrast to the earlier exposure, no droplet emission was observed from the sloped surface. Topological modifications

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Tungsten melt layer erosion due to J×B force under conditions relevant to ITER ELMs

Cited by 30 publications

References 6 publications

Analysis of tungsten melt-layer motion and splashing under tokamak conditions at TEXTOR

Analysis of tungsten melt-layer motion and splashing under tokamak conditions at TEXTOR

Experimental study of plasma energy transfer and material erosion under ELM-like heat loads

Transient induced tungsten melting at the Joint European Torus (JET)

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