Influence of carbon-dominated deposition layer on He retention and desorption in tungsten

Hu, Cui; Fujita, Hideyuki; Yajima, Miyuki; Sakurada, Shodai; Uemura, Yuji; Azuma, Keisuke; Tokitani, M.; Masuzaki, S.; Yoshida, N.; Chikada, Takumi; Oya, Yasuhisa

doi:10.1016/j.fusengdes.2016.08.006

Cited by 9 publications

(4 citation statements)

References 21 publications

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“…the case for D (see figure 5(b) where the data of figure 3(c) is reproduced at a higher magnification). This indicates that He indeed stays in the vicinity of the surface, either trapped in defects and pores or the topmost layer of the growing codeposit, as proposed in [34,36]. Our results also support the idea of saturation such that the surface densities would remain <10 21 He m −2 [37].…”

Section: Retention Of Helium In Tungsten Samplessupporting

confidence: 83%

Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges

et al. 2017

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Plasma-wall interaction was studied in the full-W ASDEX Upgrade during its dedicated helium campaign. Relatively clean plasmas with a He content of >80% could be obtained by applying ICWC discharges upon changeover from D to He. Surface analyses of W samples, however, indicated co-deposited layers with significant amounts of He and D being locally formed albeit globally D was released from the plasma-facing components. When exposing W samples to ELMy H-mode helium plasmas in the outer strike-point region of the divertor, no net erosion was observed but the surfaces had been covered with co-deposited layers. The layers were the thickest in the private flux region and extended throughout the OSP region in the case of rough and modified surfaces. Also, no clear signs of nanostructure growth or destruction could be seen The growth of such layers may impact the operation of future fusion reactors. Retention of He, for its part, remained small and uniform throughout the strike-point region.

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Section: Retention Of Helium In Tungsten Samplessupporting

confidence: 83%

Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges

et al. 2017

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“…Figure 5 presents the He release spectra of the nanochannel W film and the bulk W irra diated only by He + ions to the fluence of 3 × 10 17 ions cm −2 , or preirradiated by Kr 2+ ions to the fluence of 2.6 × 10 15 ions cm −2 and then subsequently irradiated by He + ions to the flu ence of 3 × 10 17 ions cm −2 . For setting the highest heating temperature for TDS, considering the maximum temperature limitation of the instrument, the highest temperature was set to 1173 K. Although He bubbles were observed in the irradi ated samples to the fluence of 3 × 10 17 ions cm −2 (figure 2), He bubbles will not be dissociated because the temperature for the dissociation of He atoms from the bubble needs to be at least 1400 K [31][32][33]. From the TDS spectra, it is clear to see that, under the same He fluence, the He desorption rates of the nanochannel W film are more than one order of magnitude higher than those of the bulk W whether it is postirradiated by Kr 2+ ions or not.…”

Section: Helium Desorption Behaviours Measured By Tdsmentioning

confidence: 99%

Helium retention in krypton ion pre-irradiated nanochannel W film

et al. 2017

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Nanochannel tungsten (W) film is a promising candidate as an alternative to bulk W for use in fusion applications. In previous work it has been shown to have good radiation resistance under helium (He) irradiation. To further understand the influence of the irradiationinduced displacement cascade damage on helium retention behaviour in a fusion environment, in this work, nanochannel W film and bulk W were preirradiated by 800 keV Kr 2+ ions to the fluence of 2.6 × 10 15 ions cm −2 and subsequently irradiated by 40 keV He + ions to the fluence of 5 × 10 17 ions cm −2 . The Kr 2+ ion preirradiation greatly increases helium retention in the form of small clusters and retards the formation of large clusters. It can effectively inhibit surface helium blistering under high temperature annealing. Compared with bulk W, no cracks were found in the nanochannel W film postirradiated by He + ions at high fluence. The release of helium from the nanochannel W film is more than one order of magnitude higher than that of bulk W whether they are irradiated by single He + ions or sequentially irradiated by Kr 2+ and He + ions. Moreover, swelling of the bulk W is more serious than that of the nanochannel film. Therefore, nanochannel W film has a higher radiation tolerance performance in the synergistic irradiation.

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“…Surface impurity layers have been deposited on specimens exposed in other linear plasma devices around the world, indicating that this is not an issue purely relevant to Magnum-PSI [40]. In fusion reactors, erosion, migration, and re-deposition of material occurs on a large scale resulting in altered surface compositions and chemistries that will change the material surface response to the plasma and subsequent plasma behavior [41][42][43][44][45][46]. Additionally, the FIB micrograph shows that beneath the impurity layer, the dispersoid microstructure still exists, so the material bulk is still stable and has the same microstructure and likely the same bulk mechanical properties as pre-irradiation.…”

Section: Discussionmentioning

confidence: 99%

High Flux Helium Irradiation of Dispersion-Strengthened Tungsten Alloys and Effects of Heavy Metal Impurity Layer Deposition

Lang

Kapat

Morgan

et al. 2021

Journal of Nuclear Materials

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Influence of carbon-dominated deposition layer on He retention and desorption in tungsten

Cited by 9 publications

References 21 publications

Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges

Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges

Helium retention in krypton ion pre-irradiated nanochannel W film

High Flux Helium Irradiation of Dispersion-Strengthened Tungsten Alloys and Effects of Heavy Metal Impurity Layer Deposition

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