Nb interaction with hydrogen plasma

Abstract

Plasma driven permeation of hydrogen through Nb: influence of the surface and bulk defects AIP Conf.

Hydrogen absorption capability of a niobium panel for pumping neutral atoms in divertor region

“…3 (4 · 10 23 H/m 2 ) was reached with no noticeable decrease in the absorption rate. The negligible reemission after such a significant dose at an elevated temperature (450°C) is explained by a very low value of k r0 (and a 0 ) typical for the Nb surface covered by O segregating in the form of a monolayer from the metal bulk [6,7]. Hydrogen retention in the panel was also investigated by keeping the panel at room temperature and it was found that most of the absorbed hydrogen was retained in the panel even after 48 h as indicated by open squares in Fig.…”

“…In the case of a Nb panel of 1 mm thickness at 200°C (the hydride phase does not form at T > 160°C), G H can be estimated as $10 24 H/m 2 taking d = 0.1, n H = 0.25 [7], a 0 = 10 À5 [6] and j i = 10 20 H/m 2 s. Fig. 1 shows a schematic view of the experimental device.…”

“…In steady-state regimes, a superpermeable membrane should be used for particle control [1][2][3][4][5][6], while a periodically regenerated absorption panel (simpler and cheaper) can be acceptable for an intermittent operation in non-tritium devices [7]. The Group Va metals have a combination of properties that make them most suitable for the absorption pumping of hydrogen.…”

Effects of bulk impurity concentration on the reactivity of metal surface: Sticking of hydrogen molecules and atoms to polycrystalline Nb containing oxygen

“…3͒, and therefore one can estimate the ␣ H magnitude to be in the order of at least 0.1. Atomic beam experiments with a number of metals covered by nonmetallic monolayers yielded ␣ H value in the range of 0.1-0.4 at T S ജ 298 K, 1,4,5,22,26,27 while the data on the superpermeation of H atoms through Nb covered by oxygen monolayer [1][2][3]17,18 are most self-consistent at ␣ H Ϸ 0.2-0.3. Taking that into account, we set ␣ H Ϸ 0.25 in Fig.…”

“…[1][2][3] Besides, the measurement of C O can be a method to predict the surface reactivity in addition to the conventional methods of surface analysis such as x-ray photoelectron spectroscopy and Auger electron spectroscopy ͑AES͒ incapable to measure a small concentration of holes in a near-monolayer coverage.…”