Modeling of Hydrogen Retention and Outgassing from Co‐Deposits with Distributed Energy States

Smirnov, R.D.; Krasheninnikov, S. I.; Guterl, J.; Baldwin, M.J.; Doerner, R. P.

doi:10.1002/ctpp.201410033

Cited by 8 publications

(7 citation statements)

References 6 publications

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“…Recent literature by others describes such attempts. For instance Smirnov et al [31] has made progress toward modelling fixed temperature desorption from similar Be-D co-deposits to this study. In their model, the release characteristics of baking are reconciled with the Arrhenius form of K r in [19] by the utilization of a distribution of trap energies speculated to exist on the assumption that co-deposited Be-D ought not be purely crystalline.…”

Section: Discussionmentioning

confidence: 99%

Experimental study and modelling of deuterium thermal release from Be–D co-deposited layers

2014

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A study of the thermal desorption of deuterium from 1 µm thick co-deposited Be-(0.1)D layers formed at 330 K by a magnetron sputtering technique is reported. A range of thermal desorption rates 0 β 1.0 K s −1 are explored with a view to studying the effectiveness of the proposed ITER wall and divertor bake procedure (β = 0 K s −1 ) to be carried out at 513 and 623 K. Fixed temperature bake durations up to 24 h are examined. The experimental thermal release data are used to validate a model input into the Tritium Migration and Analysis Program (TMAP-7). Good agreement with experiment is observed for a TMAP-7 model incorporating trap populations of activation energies for D release of 0.80 and 0.98 eV, and a dynamically computed surface D atomic to molecular recombination rate.

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Section: Discussionmentioning

confidence: 99%

Experimental study and modelling of deuterium thermal release from Be–D co-deposited layers

2014

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“…The model presented in [6] assumes that the power law is an effective relation, arising from the mixture of several local exponential functions in large devices. On the other hand the model presented in [8] relates the behaviour to fundamental aspects of outgassing related to hydrogen binding states. The combination of reaction-diffusion equations provides a physically solid basis [9].…”

Section: Introductionmentioning

confidence: 99%

Dynamic outgassing of deuterium, helium and nitrogen from plasma-facing materials under DEMO relevant conditions

et al. 2016

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In confined plasma magnetic fusion devices significant amounts of the hydrogen isotopes used for the fusion reaction can be stored in the plasma-facing materials by implantation. The desorption of this retained hydrogen was seen to follow a tα law with α ≈ −0.7 in tokamaks. For a pulsed fusion reactor this outgassing can define the inter-pulse waiting time. This work presents new experimental data on the dynamic outgassing in ITER grade tungsten exposed under the well-defined conditions of PSI-2 to pure and mixed D2 plasmas. A peak ion flux of 1022 D+ m−2 s is applied for up to 6 h at sample temperatures of up to 900 K. Pure D2 and mixed D2 + He, D2 + N2 and D2 + He + N2 plasmas are applied to the sample at 68 V bias. The D2, He, N outgassing at 293 K and 580 k are observed via in-vacuo quadrupole mass spectrometry covering the range of 40 s–200 000 s after exposure. The outgassing decay follows a single power law with exponents α = −0.7 to −1.1 at 293 K, but at 580 K a drop from α = −0.25 to −2.35 is found. For DEMO a pump-down time to 0.5 mPa in the order of 1–5 h can be expected. The outgassing is in all cases dominated by D2.

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“…Consequently, we introduce in this paper a R-D model including a large number of different types of traps ( > N 3 trap ) to describe hydrogen desorption from material during TDS experiments and to analyze TDSP. The present paper follows several previous works where effects of continuous distributions of traps on hydrogen retention and outgassing were investigated [9,10]. This approach has also recently attracted interest in the modeling of hydrogen retention in material damaged by neutrons [11].…”

Section: Theoretical Analysis Of Deuterium Retention In Tungsten Plas...mentioning

confidence: 82%

“…The validity of this observation can be assessed noticing that hydrogen desorption is retrapping-limited and trapped hydrogen concentrations are in equilibrium when hydrogen outgassing is described by equations (1) provided that ν ≪ Δ D tr 2 [23]. This regime also takes place for hydrogen desorption described by equations (9)…”

Section: C Modeling Of Hydrogen Retention Induced By Mutating Trapsmentioning

confidence: 85%

“…Trapping rate is assumed here to be the same for all traps ν ν ( ( ) = ) j tr tr . A previous numerical work [15] suggested that TDSP resulting from TDS experiments can be modeled using indifferently equations (1) or equations (9). The validity of this observation can be assessed noticing that hydrogen desorption is retrapping-limited and trapped hydrogen concentrations are in equilibrium when hydrogen outgassing is described by equations (1) provided that ν ≪ Δ D tr 2 [23].…”

Section: C Modeling Of Hydrogen Retention Induced By Mutating Trapsmentioning

confidence: 97%

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Theoretical analysis of deuterium retention in tungsten plasma-facing components induced by various traps via thermal desorption spectroscopy

Guterl¹,

Smirnov²,

Krasheninnikov³

et al. 2015

Nucl. Fusion

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Thermal desorption spectra (TDSP) reported in the literature and resulting from thermal desorption experiments performed on tungsten samples exposed to deuterium at several fluences are analyzed using a reaction-diffusion model including up to ten different types of traps. The use of a large number of types of traps allows accurate fits of TDSP at all fluences using a unique broad spectrum of detrapping energy. Detrapping energies found in this work are in good agreement with detrapping energies predicted by density functional theory when several hydrogen atoms are trapped in a single tungsten vacancy. The comparison between the distribution of deuterium concentrations in material and distribution of trapped deuterium concentrations in TDSP suggests that traps characterized by a broad spectrum of detrapping energy, which may correspond to tungsten vacancies, are predominantly located near the material surface (≲10 nm).

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Modeling of Hydrogen Retention and Outgassing from Co‐Deposits with Distributed Energy States

Cited by 8 publications

References 6 publications

Experimental study and modelling of deuterium thermal release from Be–D co-deposited layers

Experimental study and modelling of deuterium thermal release from Be–D co-deposited layers

Dynamic outgassing of deuterium, helium and nitrogen from plasma-facing materials under DEMO relevant conditions

Theoretical analysis of deuterium retention in tungsten plasma-facing components induced by various traps via thermal desorption spectroscopy

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