Surface cracking and melting of different tungsten grades under transient heat and particle loads in a magnetized coaxial plasma gun

Kikuchi, Yusuke; Sakuma, I.; Iwamoto, D.; Kitagawa, Y.; Fukumoto, N.; Nagata, Masayoshi; Ueda, Y.

doi:10.1016/j.jnucmat.2013.01.151

Cited by 31 publications

(7 citation statements)

References 16 publications

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“…As shown in [169] substantive voids owing to cavitation in the liquid phase are observed in W (99.95%) [162] and lead to porous re-solidified material. However, little cavitation bubbles can be found in the dense re-solidified layer of lanthanum containing W. As an example, surface cracks appeared on a pure W sample exposed to 10 plasma pulses of 0.3 MJ m −2 , while a W-Ta sample did not show surface cracks with similar pulsed plasma irradiation [170].…”

Section: Simulating Melt-damagementioning

confidence: 99%

Baseline high heat flux and plasma facing materials for fusion

et al. 2017

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In fusion reactors, surfaces of plasma facing components (PFCs) are exposed to high heat and particle flux. Tungsten and Copper alloys are primary candidates for plasma facing materials (PFMs) and coolant tube materials, respectively, mainly due to high thermal conductivity and, in the case of tungsten, its high melting point. In this paper, recent understandings and future issues on responses of tungsten and Cu alloys to fusion environments (high particle flux (including T and He), high heat flux, and high neutron doses) are reviewed. This review paper includes; Tritium retention in tungsten (K. Schmid and M. Balden), Impact of stationary and transient heat loads on tungsten (J.W. Coenen and Th. Loewenhoff), Helium effects on surface morphology of tungsten (Y. Ueda and A. Ito), Neutron radiation effects in tungsten (A. Hasegawa), and Copper and copper alloys development for high heat flux components (C. Hardie, M. Porton, and M. Gilbert).

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Section: Simulating Melt-damagementioning

confidence: 99%

Baseline high heat flux and plasma facing materials for fusion

et al. 2017

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“…Transient heat load test is also available in ACT2 facility. Structure of cracks on the W surface induced by transient load is typically less than sub mm scale [9][10][11][12]. The spot size of ACT2's electron beam is larger than the scale.…”

Section: Transient Loadmentioning

confidence: 99%

ACT2: a High Heat Flux Test Facility Using Electron Beam for Fusion Application

Hamaji

Tokitani

Masuzaki

et al. 2016

Plasma and Fusion Research

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ACT2 (Active Cooling Teststand 2), a high heat flux test facility using electron beam has been upgraded from ACT facility and started the operation. A new electron gun enables the steady state and transient heat load on actively cooled samples. ACT2 can achieve large loaded area with steady state reactor relevant heat flux (∼ 20 MW/m 2 ) up to 200 × 200 mm 2 and simulation of edge localized modes with short pulse length (∼ 100 µs).Beam profile was obtained about 9 mm with graphite probes. The heat flux is obtained by water calorimetry and measurement of the current through the samples.

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“…Coaxial plasma accelerators have many fields of applications as sources of high velocity shockwaves, as well as sources of high velocity, energetic and dense plasma [11]. Such plasmas can be used to study the interaction between plasma and solids [11][12][13], including plasma-wall interaction in fusion reactor devices [14,15]. Other applications of coaxial plasma accelerators include helicity injection in tokamaks [16], particle acceleration [17], plasma projection into vacuum and plasma propulsion [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Simulation of the inner electrode geometry effect on the rundown phase characteristics of a coaxial plasma accelerator.

2021

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A 2D computational model, incorporating the Snowplow approximation in the mass balance, is used to simulate the acceleration of an annular current sheath along two coaxial electrodes, with the inner one having either cylindrical or conical shape. The circuit, mass and momentum equations are simultaneously solved in 2D (r, z) considering initial breakdown along the insulator surface, ideal gas mass accretion by the current sheath (snowplow model) and distributed inductance along a coaxial transmission line short-circuited by the current sheath. Plasma density and electron temperature in the current sheath are estimated using standard planar shock theory. Numerical integration of the model’s equations for a given electrode geometry yields the temporal evolution of the current sheath parameters during the axial acceleration phase. In order to see the effect of the inner electrode shape on sheath parameters (i.e. transit time, kinetic energy, total mass, shape, etc.) and/or circuit properties (i.e. circuit inductance, voltage and current evolution, etc.), the portion of the inner electrode beyond the insulator was given a conical shape. By changing the cone slant in a range between ±5°, it was found that the current driven on the plasma sheath varies nonlinearly with the angle. The divergent (positive angle) electrode gives the sheath the highest kinetic energy, being twice the value corresponding to that of the straight inner electrode case, and the transit time is reduced from 1.34 to 1.20 µs. The estimates of plasma density and electron temperature indicate that the achievable ion densities are on the order of 4x1022 m-3, which corresponds to 30 % ionization, and typical temperatures at the end of the rundown phase are on the order of 8 eV. These values are comparable with those measured in experimental devices. The development of this tool will enable us to benchmark its results against an experimental installation currently close to being operational, and a future follow-up paper will be devoted to the comparison between the prediction of the rundown phase behavior and experimental results utilizing conical electrodes.

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Surface cracking and melting of different tungsten grades under transient heat and particle loads in a magnetized coaxial plasma gun

Cited by 31 publications

References 16 publications

Baseline high heat flux and plasma facing materials for fusion

Baseline high heat flux and plasma facing materials for fusion

ACT2: a High Heat Flux Test Facility Using Electron Beam for Fusion Application

Simulation of the inner electrode geometry effect on the rundown phase characteristics of a coaxial plasma accelerator.

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