Synergistic effects of high heat loading and helium irradiation of tungsten

Tokunaga, Kazutoshi; Tamura, Shinichi; Yoshida, N.; Ezato, Koichiro; Takeuchi, Masaki; Sato, K. N.; Suzuki, Satoshi; Akiba, Masato

doi:10.1016/j.jnucmat.2004.04.178

Cited by 56 publications

(45 citation statements)

References 10 publications

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“…blistering and exfoliation in particular conditions. 82) The results indicate that W surfaces modified remarkably by synergistic effect of heat and He particle loads which are similar to the loads in ITER: heat loads and He ash (one of the fusion products).…”

Section: Iter Relevant High Heat Flux Testing On Plasma Facing Surfacmentioning

confidence: 63%

ITER Relevant High Heat Flux Testing on Plasma Facing Surfaces

2005

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The current ITER design employs beryllium, carbon fiber reinforced composite and tungsten as plasma facing materials. Since these materials are exposed to high heat fluxes during the operation, it is essential to perform high heat flux tests for R&D of ITER components. Static heat loads corresponding to cycling loads during normal operation, are estimated to be up to 20 MW/m 2 in the divertor targets and around 0.5 MW/m 2 at the first wall in ITER. For the static high heat flux testing, tests in electron beam facilities, particle beam facilities, IR heater and in-pile tests have been performed. Another type, more critical heat loads, which have high power densities and short durations, corresponding to transient events, i.e. plasma disruption, vertical displacement events (VDEs) and edge localized modes (ELMs) deliver considerable heat flux onto the plasma facing materials. For this purpose, tests in electron beam (short pulses), plasma gun and high power laser facilities have been carried out. The present work summarizes the features of these facilities and recent experimental results as well as the current selection of ITER plasma facing components.

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Section: Iter Relevant High Heat Flux Testing On Plasma Facing Surfacmentioning

confidence: 63%

ITER Relevant High Heat Flux Testing on Plasma Facing Surfaces

2005

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“…In a power reactor divertor there will be a D/T plasma with a concentration of He in the range of 5-10%. Synergistic effects of simultaneous irradiation of tungsten surfaces with He particles and high heat flux were observed for instance in [1,2]. The formation of surface and near-surface features with typical dimensions in the range of nanometres to micrometres under irradiation with He or H/He mixtures has been reported for tungsten from a number of plasma or high heat flux experiments [3,4,5].…”

Section: Introductionmentioning

confidence: 92%

“…1)) is 4.1×10 -3 and is assumed to be independent of temperature. The solid lines in figure 1 represent the resulting erosion using equation (1). The dashed lines represent the above erosion from physical sputtering data, which is assumed to be temperature-independent.…”

Section: Erosion Data Analysismentioning

confidence: 99%

“…In the following we investigate two of these possible causes. The most obvious is the formation of a distorted surface layer, as shown in several experiments (see references [1][2][3][4][5][6][7][8][9][10][11]), which is investigated as a function of fluence and temperature in section 3.2.1. The second is the dependence of the sputtering yield on the crystal orientation.…”

Section: Investigation Of Possible Mechanismsmentioning

confidence: 99%

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Tungsten erosion under combined hydrogen/helium high heat flux loading

et al. 2014

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We investigated the erosion behaviour of tungsten under irradiation with a fusion reactorrelevant H/He mixture of 94%/6% at a power density of 10 MW/m². The investigated surface temperatures range up to 2000°C and the range of the applied fluence was up to 7×10 25 m -2 . The erosion yield we observe exceeds the value expected from physical sputtering data by a factor of 2. In addition we observe an Arrhenius-like increase of the erosion yield with temperature with an activation energy of 0.04 eV.

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“…Tungsten (W) is a promising candidate for future use in fusion reactors as a plasma facing material, due to its high melting point, high thermal conductivity, low tritium inventory and other favorable characteristics [1,2]. During such usage it will be exposed to both particle irradiation and high heat flux loads.…”

Section: Introductionmentioning

confidence: 99%

Effects of temperature on surface modification of W exposed to He particles

Greuner

Yuan

et al. 2014

Journal of Nuclear Materials

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The effect of combined heating and helium particle flux on annealed tungsten samples has been studied in the neutral beam facility GLADIS. He beams with power densities of 2.4 MW/m 2 and 9.5 MW/m 2 were used to adiabatically load the samples to peak surface temperatures from ~ 950 °C (1223 K) to ~ 2700 °C (2973 K). Changes in the surface morphology resulting from combined heat and the flux exposure were studied for He fluences up to 3×10 22 /m 2 . Typical structures for the sample loaded at ~ 950 °C (1223 K) were blisters with a clear grain orientation dependence and the largest blisters formed on grains with <001> surface normal. However at higher temperatures, blistering was more easily suppressed for grains near this orientation because the growth of larger blister takes place more slowly. An evolution from a "porous structure" to a "coral-like structure" with increasing fluence was observed on the samples loaded at the highest temperature. Based on these results mechanisms for surface modification at different temperatures are discussed and a texture with <001> parallel to the normal direction of the grains is suggested to optimize the plasma facing material due to their stronger resistance to early stage blistering.

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Synergistic effects of high heat loading and helium irradiation of tungsten

Cited by 56 publications

References 10 publications

ITER Relevant High Heat Flux Testing on Plasma Facing Surfaces

ITER Relevant High Heat Flux Testing on Plasma Facing Surfaces

Tungsten erosion under combined hydrogen/helium high heat flux loading

Effects of temperature on surface modification of W exposed to He particles

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