Micro-/nano-characterization of the surface structures on the divertor tiles from JET ITER-like wall

Tokitani, M.; Miyamoto, M.; Masuzaki, S.; Fujii, Yusuke; Sakamoto, R.; Oya, Yasuhisa; Hatano, Yuji; Otsuka, Teppei; Oyaidzu, M.; Kurotaki, H.; Suzuki, Takahiro; Hamaguchi, Dai; Isobe, K.; Asakura, N.; Widdowson, A.; Rubel, M.

doi:10.1016/j.fusengdes.2017.01.002

Cited by 14 publications

(13 citation statements)

References 14 publications

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“…The mechanism by which He influences D retention in co-deposited Be layer is not clear. A post-mortem transmission electron microscope analysis of an inner divertor tile from JET-ILW (where no He was present) shows the presence of bubbles in the Be-rich co-deposited layers [23], however no interconnection between the bubbles has been reported. On the other hand, He ion implantation in bulk Be can lead to a creation of interconnected bubbles and channels, as shown in [24].…”

Section: Discussionmentioning

confidence: 99%

The influence of helium on deuterium retention in beryllium co-deposits

Založnik¹,

Baldwin²,

Doerner³

et al. 2018

Journal of Nuclear Materials

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Tritium co-deposition with materials from the plasma-facing components is expected to be the main contributor to tritium retention in ITER. Since He will also be present in the plasma as fusion ash during the DT campaign, this study focuses on the effect of He on D retention in Be co-deposits. The PISCES-B linear plasma device was used to create co-deposited BeD He layers for various deposition temperatures (295 K-475 K) and He concentrations in D − αHe plasma mixtures (0 ≤ α ≤ 0.1). Thermal desorption spectroscopy and nuclear reaction analysis were used to determine the D concentration in co-deposits. For the lowest He concentration (1%) an increase of D retention was observed for the deposition at room temperature, whereas for higher He concentrations a declining trend of D retention was found. Including 10% of He in the plasma is found to reduce D retention at deposition temperatures below 425 K and have a negligible effect at higher deposition temperatures.

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Section: Discussionmentioning

confidence: 99%

The influence of helium on deuterium retention in beryllium co-deposits

Založnik¹,

Baldwin²,

Doerner³

et al. 2018

Journal of Nuclear Materials

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“…As explained in our previous work of Ref. [15], all JET divertor tiles except tile 5 consist of W coated CFC. Thickness of W-coating layer is 10-20 µm [8,18].…”

Section: Methodsmentioning

confidence: 96%

“…Fig. 1 shows the poloidal cross-section of the JET ILW divertor with three representative plasma geometries and positions of all extracted surface samples with size of 17 mm in diameter and 5 mm in thickness transferred to International Fusion Energy Research Centre (IFERC), QST, Rokkasho, Japan [15,17]. In this study, samples of 8-10b, 7-1a and 6-6b from the outer divertor tiles of upper, vertical and horizontal, and samples of 3-6a from the inner vertical divertor tiles were selected for analysis.…”

Section: Methodsmentioning

confidence: 99%

“…Previous studies have shown, that the apron of tile 1 is the main deposition part of the eroded Be from the first wall [13], and the highest amount of the D retention among all of the inner tiles was detected on this tile [10]. One of the noteworthy results from the Japanese group is the micro/nanoscopic observation of the subsurface region of the samples from the inner divertor tiles 1, 3 and 4, i.e., upper (apron), vertical and horizontal targets, respectively [15]. The formation of the thick stratified mixed-material deposition layer, composed of Be, W, Ni, O and C on tiles 1 and 4, and erosion on tile 3 were identified.…”

Section: Introductionmentioning

confidence: 94%

“…The transmission electron microscope (TEM) studies in Ref. [15] identified a dense nano-size bubble-like structure with size of over 100 nm in that Be rich layer. Judging from the size and density of the bubbles, formation of the bubble-like structure seems to be related to D retention in the layer.…”

Section: Introductionmentioning

confidence: 99%

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Plasma-wall interaction on the divertor tiles of JET ITER-like wall from the viewpoint of micro/nanoscopic observations

Tokitani

Miyamoto

Masuzaki

et al. 2018

Fusion Engineering and Design

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Micro/nanoscopic observations on the surface of the divertor tiles used in the first campaign (2011)(2012) of the JET tokamak with ITER-like Wall (JET ILW) have been carried out by means of several material analysis techniques. Previous results from the inner divertor were reported for a single poloidal section of the tile numbers 1, 3 and 4, i.e., upper, vertical and horizontal targets, respectively. The formation of the thick stratified mixed-material deposition layer on tiles 1 and 4, and erosion on tile 3 were identified. This study is mostly focused on the outer divertor: tiles 6, 7 and 8. In contrast to the inner tile, remarkable surface modifications have not been observed on the vertical target (tiles 7 and 8) where sputtering erosion and impurity deposition would have been almost balanced. Only a specific part of tile 6 (horizontal target) located near the exhaust channel was covered with a stratified ("geological-like") mixed-material deposition layer which mainly included Be and Ni with the thickness of ~2 µm. Special feature of this mixed layer was that a certain amount of nitrogen (N) was clearly detected in the layer. Since the concentration of N varied with the depth position, it could be depended on the amount of that gas puffed for plasma edge cooling during the JET experimental campaign. In addition to the outer divertor tiles, a very interesting feature of the local erosion and deposition effects is reported in this paper.

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