Hydrogen isotope transport across tungsten surfaces exposed to a fusion relevant He ion fluence

Abstract

Tungsten targets are exposed to controlled sequences of D 2 and He, and He and D 2 plasma in the Pisces-A linear plasma device, with a view to studying the outward and inward transport of D across a He implanted surface, using thermal desorption mass spectrometry. Differences in transport are interpreted from changes in peak desorption temperature and amplitude for D 2 release, compared against that of control targets exposed to just D 2 plasma. Desorption data are modeled with Tmap-7 to infer the nature by which He leads to the 'reduced inventory' effect for H isotope uptake. A dual segment (surface-30 nm, bulk) W Tmap-7 model is developed, that simulates both plasma exposure and thermal desorption. Good agreement between desorption data and model is found for D 2 release from control targets provided that the implanted flux is reduced, similar to that reported by others. For He affected release, the H isotope transport properties of the surface segment are adjusted away from control target bulk values during the computation. Modeling that examines outward D transport through the He implanted layer suggests that a permeation barrier is active, but bubble induced porosity is insufficient to fully explain the barrier strength. Moderately increased diffusional migration energy in the model over the He affected region, however, gives a barrier strength consistent with experiment. The same model, applied to inward transport, predicts the reduced inventory effect, but a further reduction in the implanted D flux is necessary for precise agreement.

Reduced D trapping by plasma-implanted He nanobubbles in radiation damaged tungsten

“…Doerner 2 , C. Xu 4 , J.P. Zhu 4 and E.G. Fu 4,a It is thought that this is caused by the so-called barrier effect in which the implanted He ions form a thin (few tens of nm) He nanobubble layer in the sample and act to reduce the D retention either via the formation of interconnected pathways to the sample surface, leading the D ions to diffuse back to the plasma and resulting in the D retention decreasing, or by the formation of a diffusion barrier to the D atoms, or both [6]. On the other hand, many studies [7][8][9][10][11] have shown that radiation damage in W induced e.g.…”

Comparative Passivation of Si(100) by H2 and D2 Atmospheres under Simultaneous Xe+ Bombardment: An X-ray Photoelectron Spectroscopy Analysis

“…11,12 Furthermore, the research on the retention of hydrogen and isotopes on the surface holds significant potential for nuclear fusion energy. 13,14 Tokamak reactors commonly employ hydrogen and isotopes as fuel sources, and the interaction of these species in the plasma state on the inner walls of the reactor has garnered significant attention in current studies. 15−18 Moreover, hydrogen storage assisted by plasma has garnered attention from several research groups.…”

“…H 2 and D 2 are commonly applied to passivate Si substrates in the microelectronic industry to prevent contamination, such as H 2 O, which is present in the base pressure of standard vacuum vessels. − Additionally, passivation finds various applications in thin film technologies, serving as anticorrosive protection and interface functionalization and creating hard coatings. − Passivation of dangling bonds is crucial in hydrogenated amorphous silicon materials. , Furthermore, the research on the retention of hydrogen and isotopes on the surface holds significant potential for nuclear fusion energy. , Tokamak reactors commonly employ hydrogen and isotopes as fuel sources, and the interaction of these species in the plasma state on the inner walls of the reactor has garnered significant attention in current studies. − Moreover, hydrogen storage assisted by plasma has garnered attention from several research groups. , To control the physical–chemical mechanisms of passivation, factors like the surface state, temperature, and sticking coefficient must be taken into consideration. − …”

A critical review of experiments on deuterium retention in displacement-damaged tungsten as function of damaging dose

“…Therefore, it seems obvious that the retention of hydrogen isotopes should closely follow the evolution of damage with the dose. However, hydrogen isotopes retention is a complicated phenomenon because it is the result of many different parameters such as the material grade (structure and impurity level) [24], the material temperature [25], surface condition [26], and it depends critically on the incoming particle flux, its energy and composition as hydrogen bubble formation occurs above a certain solute concentration [27,28]. Eventually, macroscopic defects, such as blisters, develop [24,[29][30][31][32].…”