Deuterium retention and morphological modifications of the surface in five grades of tungsten after deuterium plasma exposure

Balden, M.; Manhard, A.; Elgeti, S.

doi:10.1016/j.jnucmat.2014.05.018

Cited by 67 publications

(66 citation statements)

References 35 publications

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“…Plastic deformation as well as dislocation loop punching start with pressure build up inside a cavity. To cause plastic deformation of grains, pressures in the range of a few hundred MPa have been reported [27], for plastic deformation caused by dislocation loop punching a few GPa is needed [9,41]. From our results we are not able to distinguish between these two mechanisms.…”

Section: Discussioncontrasting

confidence: 61%

“…Sample A, which we call the low-flux sample, was exposed in PlaQ [27]. The other samples (B -D) were exposed to high-flux deuterium plasmas in Pilot-PSI.…”

Section: Deuterium Plasma Exposurementioning

confidence: 99%

“…The energy was varied in 6 steps from 690 keV to 4.0 MeV to determine the deuterium concentration down to a depth of 6 µm. The low-flux sample (A) was analysed using slightly different energies [27]. The depth profiles of retained deuterium were calculated from the measured proton energy distributions by use of the NRA-DC program [30].…”

Section: Target Analysismentioning

confidence: 99%

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Surface morphology and deuterium retention of tungsten after low- and high-flux deuterium plasma exposure

Hoen¹,

Balden²,

Manhard³

et al. 2014

Nucl. Fusion

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Abstract.The surface morphology and deuterium retention were investigated of polycrystalline tungsten targets that were exposed to deuterium plasmas at widely varying conditions. By changing only one parameter at a time, the isolated effects of flux, time and pre-damaging on surface modifications and deuterium retention were studied. The sample exposed to low-flux plasma (10 20 m −2 s −1 ) is mostly smooth with only a few areas containing very large blisters (50 -500 µm). The samples exposed to high-flux plasmas (10 24 m −2 s −1 ) show large numbers of smaller blisters (1 -10 µm) and in addition even smaller protrusions (<750 nm). The size of the blisters and their density strongly increase with fluence. Pre-damaging tungsten with MeV ions leads to less blisters but to more protrusions. In addition to these (sub-)micrometer-sized structures, all samples show formation of nanostructures. Comparison of a low-flux and high-flux sample exposed to similar fluence showed that the variation in morphology is dominated by the flux differences. It is shown that the blisters and protrusions originate in inter-and intra-granular cavities, respectively. The depth of the cavities underneath the surface correlates well with the depth distributions of the retained deuterium. Trapping of significant amounts of deuterium therefore seems to take place in and/or close to these cavities and gives rise to an additional peak in the thermal desorption spectrum at 700 K.PACS numbers: 28.52.Fa, 28.52. Nh, 52.40.Hf, 52.77.Dq, 61.80.Jh, Submitted to: Nuclear Fusion Surface morphology and deuterium retention at high-flux deuterium plasmas 2

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Section: Discussioncontrasting

confidence: 61%

“…Sample A, which we call the low-flux sample, was exposed in PlaQ [27]. The other samples (B -D) were exposed to high-flux deuterium plasmas in Pilot-PSI.…”

Section: Deuterium Plasma Exposurementioning

confidence: 99%

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Surface morphology and deuterium retention of tungsten after low- and high-flux deuterium plasma exposure

Hoen¹,

Balden²,

Manhard³

et al. 2014

Nucl. Fusion

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“…Consequently, the cracks start to grow from those cavities, well observed by scanning electron microscopy (SEM). In case of recrystallized and large grain size material, the formation of cavities deeper than several micrometers was also observed [12]. However, besides the SEM-visible cavities, a significant concentration of D is present in nanometric bubbles, formed as a result of plasma exposure and located within first several micrometers, as was recently reported by direct transmission electron microscopy (TEM) observations [13].…”

Section: Introductionsupporting

confidence: 55%

Microstructural modifications in tungsten induced by high flux plasma exposure: TEM examination

et al. 2016

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We have performed microstructural characterization using transmission electron microscopy (TEM) techniques to reveal nanometric features in the sub-surface region of tungsten samples exposed to high flux, low energy deuterium plasma. TEM examination revealed formation of a dense dislocation network and dislocation tangles, overall resulting in a strong increase in the dislocation density by at least one order of magnitude as compared to the initial one. Plasmainduced dislocation microstructure vanishes beyond a depth of about 10 μm from the top of the exposed surface where the dislocation density and its morphology becomes comparable to the reference microstructure. Interstitial edge dislocation loops with Burgers vector a 0 /2〈111〉 and a 0 〈100〉 were regularly observed within 6 μm of the sub-surface region of the exposed samples, but absent in the reference material. The presence of these loops points to a co-existence of nanometric D bubbles, growing by loop punching mechanism, and sub-micron deuterium flakes, resulting in the formation of surface blisters, also observed here by scanning electron microscopy.S Online supplementary data available from stacks.iop.org/PSTOP/T167/014030/mmedia

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“…First results using exactly this material with the same surface finish and heat treatments, but with a less detailed characterisation, were already published [5,6,7,8].…”

Section: Introductionmentioning

confidence: 99%

Quantitative Microstructure and Defect Density Analysis of Polycrystalline Tungsten Reference Samples after Different Heat Treatments

Manhard

Balden

Elgeti

2015

Practical Metallography

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In order to provide a solid basis for the correlation of microstructure and hydrogen isotope retention in tungsten, reference samples with different microstructures were prepared from a single batch of polycrystalline tungsten by standardised polishing and heat treatment procedures. Representative samples were analysed by scanning electron microscopy and scanning transmission electron microscopy as well as by electron backscatter diffraction. We show that if the annealing temperature is increased from 1200 to 1500 K, practically only the density of dislocations and grain boundaries with very small misorientations of less than 2° is reduced, while for annealing at 1700 and 2000 K, also the density of high-angle grain boundaries is reduced due to grain growth. Furthermore, the dislocation density is reduced by nearly two orders of magnitude compared to tungsten annealed at 1200 K. We also comment on two different textures on the front and rear side of the samples that were observed both by X-ray diffraction and EBSD.

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Deuterium retention and morphological modifications of the surface in five grades of tungsten after deuterium plasma exposure

Cited by 67 publications

References 35 publications

Surface morphology and deuterium retention of tungsten after low- and high-flux deuterium plasma exposure

Surface morphology and deuterium retention of tungsten after low- and high-flux deuterium plasma exposure

Microstructural modifications in tungsten induced by high flux plasma exposure: TEM examination

Quantitative Microstructure and Defect Density Analysis of Polycrystalline Tungsten Reference Samples after Different Heat Treatments

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