Hydrogenic retention in tungsten exposed to ITER divertor relevant plasma flux densities

Wright, G.M.; Kleyn, A.W.; Alves, E.; Alves, L.C.; Barradas, N.P.; Rooij, G.J. van; Lange, A. J. van; Shumack, A.; Westerhout, J.; Al, R.S.; Vijvers, W.A.J.; Groot, B. de; Pol, M. J. van de; Meiden, H.J. van der; Rapp, J.; Cardozo, N.J. Lopes

doi:10.1016/j.jnucmat.2009.01.173

Cited by 14 publications

(10 citation statements)

References 15 publications

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“…However, previous work has shown no dependence of retention on plasma flux or fluence for unirradiated targets in the high temperature regime [16,17]. The possibility of a flux or fluence dependence in the low temperature regime is addressed later in this report.…”

Section: Spatial and Depth Distribution Of Dmentioning

confidence: 83%

“…Many previous studies have postulated that high rates of ion implantation into low solubility metals, such as W, can result in the production of trap sites through the super-saturation of the implantation zone creating stresses in the lattice [15,[19][20][21]. Previous work on Pilot-PSI has shown this is not a strong contributor in the high-temperature regime [16], likely due to high hydrogenic diffusion rates at these temperatures. At lower temperatures, NRA analysis shows that local concentrations of D in un-irradiated targets has increased when compared to irradiated targets (Fig.…”

Section: Spatial and Depth Distribution Of Dmentioning

confidence: 99%

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Hydrogenic retention in irradiated tungsten exposed to high-flux plasma

et al. 2010

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Two sets of identical tungsten (W) targets are irradiated at 300 K with 12.3 MeV W 4+ ions to peak damage levels ranging from 0.5-10 displacements per atom (dpa). This results in a damage profile that is peaked at ~0.8 µm and extends to a depth of ~1.5 µm. Both sets of targets are exposed to high-density (n e,center = 3 x 10 20 m -3 ), lowtemperature (T e,center = 1.6 eV) deuterium (D) plasma in Pilot-PSI. One set of irradiated targets is exposed at high surface temperatures (T W = 950 -680 K) and the other at low surface temperatures (T W = 480 K -340 K). The surface temperature is determined by the local plasma conditions. Nuclear reaction analysis (NRA) is used to determine the D depth profiles at specific radial locations, thus giving a surface temperature scan of the D retention in the damaged W. Global retention is determined by thermal desorption spectroscopy, which yields total D retained in the target and also gives information of the different types of lattice defects that are trapping the D in the W lattice. The main results are that there is no measurable difference between the different dpa levels, implying a saturation of the retention enhancement at a level ≤0.5 dpa. For both irradiated and unirradiated tungsten, a peak in the retention is seen at T W = 480 K, however the W 4+ irradiation clearly enhances the retention. This enhancement is also temperature dependent and increases with increasing surface temperature up to an enhancement by a factor of 15-23 at T W = 950 K. At the lowest surface temperatures, a fluence dependence appears since the implanted deuterium is diffusion limited to only a small fraction of the irradiated zone. TDS spectra show an enhancement of both low energy trap sites and high energy trap sites. For these conditions, diffusion-limited, low fill fraction trapping determines the hydrogenic retention of the W.

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Section: Spatial and Depth Distribution Of Dmentioning

confidence: 83%

Section: Spatial and Depth Distribution Of Dmentioning

confidence: 99%

Hydrogenic retention in irradiated tungsten exposed to high-flux plasma

et al. 2010

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“…The reasoning behind exposing these targets in the ''as received'' condition was to best approximate the condition of the tungsten surfaces in a tokamak divertor during typical operations. It is already well-established that pre-annealing and polishing targets can affect retention properties, namely that pre-annealing of targets can reduce retention [6,7], while polishing can increase retention [8].…”

Section: Methodsmentioning

confidence: 99%

“…4 plots retained fraction (D retained /D þ incident ) as a function of target surface temperature for W and Mo over a range of incident plasma flux densities. Plotting retained fractions normalizes the data to plasma fluence but it should be noted that previous work [8] has shown there to be no discernable fluence dependence of retention for these plasma conditions. TDS results presented in [8] for the W targets show a total retention a factor of $2 higher than integrated NRA results, likely indicating that the retention extends beyond the 3 lm probing depth of the 3 He ion beam.…”

Section: à3mentioning

confidence: 99%

“…Plotting retained fractions normalizes the data to plasma fluence but it should be noted that previous work [8] has shown there to be no discernable fluence dependence of retention for these plasma conditions. TDS results presented in [8] for the W targets show a total retention a factor of $2 higher than integrated NRA results, likely indicating that the retention extends beyond the 3 lm probing depth of the 3 He ion beam. This is not surprising given the high temperatures of the exposure leading to high diffusion rates of hydrogen in W. Fig.…”

Section: à3mentioning

confidence: 99%

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Materials research under ITER-like divertor conditions at FOM Rijnhuizen

Wright¹,

Westerhout²,

Al³

et al. 2011

Journal of Nuclear Materials

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a b s t r a c tAt FOM Rijnhuizen, linear plasma generators are used to investigate plasma-material interactions under high-density (610 21 m À3), low-temperature (65 eV) plasma bombardment. Research into carbon-based materials has been focused on chemical erosion by hydrogen plasmas. Results from plasma exposure to high-flux (>10 23 H + /m 2 s) and low-temperature hydrogen plasma indicate silicon carbide has a lower relative rate of gross erosion than other carbon-based materials (e.g. graphite, diamond, carbon-fiber composites) by a factor of 7-10. Hydrogenic retention is the focus of research on tungsten and molybdenum. For target temperatures of 700-1600 K, the temperature dependence of hydrogenic retention is the dominant factor. Damage to the surface by heavy ion irradiation has shown to enhance retention by a factor of 2.5-4.1. Thermal stressing of W via. e-beam thermal cycling also enhances hydrogenic retention by a factor of 2.1 ± 0.2, likely due to the introduction of thermal defects, which act as trapping sites for implanted hydrogenic isotopes.

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Investigating Synergistic Effects on W Performance with Magnum-PSI

Thompson

2018

Springer Theses

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Hydrogenic retention in tungsten exposed to ITER divertor relevant plasma flux densities

Cited by 14 publications

References 15 publications

Hydrogenic retention in irradiated tungsten exposed to high-flux plasma

Hydrogenic retention in irradiated tungsten exposed to high-flux plasma

Materials research under ITER-like divertor conditions at FOM Rijnhuizen

Investigating Synergistic Effects on W Performance with Magnum-PSI

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