Influences of Porosity on Hydrogen Diffusion and Retention in Lithiated Porous Tungsten

Hybrid liquid lithium – porous tungsten materials are being considered as candidate plasma facing components due to their ability to maintain a continuously replenishable low-z plasma interface while tolerating both the high steady-state and transient heat fluxes in the high-duty cycle environment of a fusion reactor [1].

Studies on the diffusion and retention of hydrogen in hybrid liquid Li- porous tungsten substrates are being performed at the DIONISOS experiment at MIT. Lithiated porous tungsten samples made by spark plasma sintering are irradiated with deuterium using a fluence of 1024/m2 at solid (room temperature) and liquid (200° C) states. Virgin porous tungsten samples (e.g. without Li) are used as controls (room temperature and T = 200°C) to compare D diffusion in porous W with and without Li. Furthermore, highly dense tungsten samples with the same temperature and lithium parameters as the porous W samples are also used as controls to investigate the effects of the samples’ bulk morphology on the D diffusivity. In-situ Ion Beam Analisis (IBA) is then used to obtain information on the depth distribution of deuterium in the samples. After IBA measurements, In-situ mass spectrometry is performed using a Residual Gas Analyzer (RGA) to quantify the deuterium retained in the samples. Results will be discussed in the context of how deuterium is retained and is diffusing through the samples, and how the porous morphology of the samples affects this dynamic.