Numerical analysis of TDS spectra under high and low flux plasma exposure conditions

Abstract

Recently developed numerical model, based on the dislocation-driven nucleation of gas bubbles, is used to analyse experimental results on deuterium retention in tungsten under ITER relevant plasma exposure conditions. Focus is put on understanding the relation between exposure temperature and flux on primary features of thermal desorption spectra: peak positions and intensities of the desorption flux. The model allows one to relate the peak positions with the size of plasma induced deuterium bubbles and envisage exposure conditions (temperature and flux) for their formation. Based on the performed analysis, dedicated experimental conditions to validate the model are proposed.

Hydrogen atom-ion synergy in surface lattice modification at sub-threshold energy

“…Further increasing the irradiation temperature until created vacancies can no longer stably trap solute HI atoms may suppress or even prevent SSL formation. Experimental detrapping energies of D from vacancies or their clusters in W [39] agree well with theoretical predictions [40,41] and correspond to D release between ~500 and ~850 K [39]. Hence plasma irradiations at temperatures above 900 K should suppress HI trapping in vacancies thereby preventing SSL formation.…”

“…[18]) but has a similar dependence on incident and T as 𝐶 𝑚𝑎𝑥 𝐻𝐼 . Thus, as an important practical insight, SSL formation cannot be prohibited by elevated temperatures during exposure to a given particle flux within the thermal stability limits of HI trapping in vacancies [39][40][41], because at elevated temperatures also the HI mobility increases. To demonstrate this prediction, we performed both 415-eV H-and 215-eV D-plasma exposures at different temperatures under otherwise identical conditions.…”

“…This poses the pertinent question whether a similar SSL formation as observed here for HI plasma-exposed W might also occur on He-irradiated W surfaces. Although at much lower concentration that the HIs (D, T), He is an inevitable component in fusion plasmas, and as an implanted impurity in W lattices He interacts even more strongly with vacancy defects (interaction energy ~ 4 eV) [42] than HIs (≤~1.5 eV [39][40][41]). In principle, stabilization of temporary vacancies by implanted He and a potential synergistic formation of a He-SSL might therefore also be expected to occur on W surfaces under He plasma irradiation.…”

Molecular dynamics simulation of hydrogen and helium trapping in tungsten

“…Based on the results of the static simulations the following conclusions can be drawn. [41][42][43] or Kinetic Monte Carlo simulations [44]. Together with the data for diffusion and thermal stability of mixed He M -H N clusters reporter earlier [27], this paper provides the parameters needed for such simulations.…”

Irradiation hardening induced by blistering in tungsten due to low-energy high flux hydrogen plasma exposure

“…It is known that blister formation includes the nucleation of cavity/crack and growth of these nuclei. The nucleation mechanisms of cavities in recrystallized W are suggested as the dislocation loop punching initially from vacancies [12][13][14], dislocations [4,15,16], and H platelet aggregations [17], but not yet experimentally confirmed. While, the growth mechanisms of cavities are generally acknowledged as the plastic deformation [11,18,19], dislocation loop punching [20] and agglomeration of H-vacancy complexes [21,22].…”