Hydrogen Retention Characterization of Lithiated PFCs Using the Sample Exposure Probe in LTX-β

Hybrid liquid lithium (Li) – porous tungsten (W) materials are being considered as candidate plasma facing components due to their ability to maintain a continuously replenishable low- Z plasma interface while tolerating the high steady-state and transient heat fluxes encountered in a fusion reactor [1].

Surface science studies are being performed on porous W samples using the Sample Exposure Probe (SEP) [2] in LTX-β. The SEP can be used to perform in situ temperature programmed desorption (TPD) and in vacuo secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). An oxidized and carbon (C) contaminated porous W sample was exposed to a conventional neon (Ne) glow discharge cleaning (GDC) cycle in LTX-β. Characterization by SIMS, XPS and TPD after the Ne GDC showed that the Ne GDC reduced the W oxides and removed all C contamination from both the surface and subsurface of the sample. H retention studies are now being conducted on the Ne GDC cleaned sample. The sample is being exposed in both lithiated (solid and liquid) and not non-lithiated states on the midplane of the low-field side of LTX-β to a hydrogen (H⁺) fluence of ~ 10²² /m². TPD is used to quantify the amount of H retained in the samples and to complement SIMS measurements to investigate the surface chemical changes of the sample after plasma exposure. Solid W and stainless steel samples are also used as controls.

[1] Nygren, R. E., and F. L. Tabarés Nucl. Mater. Energy (2016).

[2] A. Maan et al IEEE Transactions on Plasma Science (2020).