Retention in tungsten resulting from extremely high fluence plasma exposure

Doerner, R.; Baldwin, M.J.; Lynch, T.; Yu, J. H.

doi:10.1016/j.nme.2016.04.008

Cited by 37 publications

(24 citation statements)

References 13 publications

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“…A fit to these data is also shown as the red line in Figure 4. As discussed elsewhere [36], the retention probability decreases significantly as the material temperature during plasma exposure is increased.…”

Section: Discussionmentioning

confidence: 70%

“…Using these data, and taking ptrap to be given then by the ratio of the retained D inventory to the total ion fluence to the surface, we can then examine the evolution of ptrap, vs. plasma ion fluence. Figure 4 shows this result for several types of plasma--exposed W. The open red circles show ptrap, vs. plasma ion fluence for undamaged W exposed to D plasmas in PISCES plasmas, where the W samples were held at 643 K. A detailed description of these PISCES exposures is available elsewhere [36]. These data show a precipitous drop in ptrap with increased plasma fluence, presumably due to the fact that as the fluence is raised, the near--surface intrinsic traps become saturated with D. The resulting saturated near--surface region is then more likely to release D back to the plasma, thereby reducing ptrap.…”

Section: Discussionmentioning

confidence: 99%

“…The earlier discussion of TBR motivates us to estimate the trapping probability, ptrap, which was introduced earlier in this paper as an important parameter that affects the achievable TBR. Recent work [36] provides measurements of retained D inventory vs plasma fluence for undamaged tungsten. Using these data, and taking ptrap to be given then by the ratio of the retained D inventory to the total ion fluence to the surface, we can then examine the evolution of ptrap, vs. plasma ion fluence.…”

Section: Discussionmentioning

confidence: 99%

“…Vertical colored areas show the expected fluence to a DEMO first wall for several operational periods for an assumed first-wall ion flux of 10 20 ions/m 2 --sec. Undamaged PISCES--B data points derived from published results [36]. Neutron data from Shimada et al [28].…”

Section: Discussionmentioning

confidence: 99%

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Deuterium retention and thermal conductivity in ion-beam displacement-damaged tungsten

Tynan

Doerner

Barton

et al. 2017

Nuclear Materials and Energy

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Retention of plasma-implanted D is studied in W targets damaged by a Cu ion beam at up to 0.2 dpa with sample temperatures between 300 K and 1200 K. At a D plasma ion fluence of 10 24 /m 2 on samples damaged to 0.2 dpa at 300 K, the retained D retention inventory is 4.6x10 20 D/m 2 , about ~5.5 times higher than in undamaged samples. The retained inventory drops to 9x10 19 D/m 2 for samples damaged to 0.2 dpa at 1000 K, consistent with onset of vacancy annealing at a rate sufficient to overcome the elevated rate of ion beam damage; at a damage temperature of 1200 K retention is nearly equal to values seen in undamaged materials. A nano-scale technique provides thermal conductivity measurements from the Cuion beam displacement damaged region. We find the thermal conductivity of W damaged to 0.2 dpa at room temperature drops from the un-irradiated value of 182±3.3 W/m·K to 53±8 W/m·K.

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Deuterium retention and thermal conductivity in ion-beam displacement-damaged tungsten

Tynan

Doerner

Barton

et al. 2017

Nuclear Materials and Energy

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“…Only in recent experiments at PISCES-B W targets were exposed to a deuterium (D) plasma to fluences up to 210 28 D/m 2 . However, the exposures were carried out only at one temperature of 640 K and the surface modifications of the exposed targets were not studied in detail [20].…”

Section: Introductionmentioning

confidence: 99%

Deuterium trapping and surface modification of polycrystalline tungsten exposed to a high-flux plasma at high fluences

et al. 2017

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Deuterium (D) retention and surface modifications of hot-rolled polycrystalline tungsten (W) exposed to a low-energy (40 eV/D), high-flux (2-5×10 23 D/m 2 s) D plasma at temperatures of 380 K and 1140 K to fluences up to 1.2×10 28 D/m 2 have been examined by using nuclear reaction analysis, thermal desorption spectroscopy, and scanning electron microscopy. The samples exposed at 380 K exhibited various types of surface modifications: dome-shaped blister-like structures, stepped flat-topped protrusions, and various types of nanostructures. It was observed that a large fraction of the surface was covered with blisters and protrusions, but their average size and the number density showed almost no fluence dependence. The D depth distributions and total D inventories also barely changed with increasing fluence at 380 K. A substantial amount of D was retained in the subsurface region, which thickness correlated with the depth where the cavities of blisters and protrusions were located. It is therefore suggested that defects appearing during creation of blisters and protrusions govern the D trapping in the investigated fluence range. In addition, a large number of small cracks was observed on the exposed surfaces, which can serve as fast D release channels towards the surface, resulting in a reduction of the effective D influx into the W bulk. On the samples exposed at 1140 K no blisters and protrusions were found.However, wave-like and faceted terrace-like structures were formed instead. The concentrations of trapped D were very low (<10 5 at. fr.) after the exposure at 1140 K.

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