Experimental investigation of a novel liquid metal plasma facing component with pre-filled microstructures

TL;DR

This study introduces a 3D-printed microstructured liquid metal surface with pre-filled microstructures that enhances stability and wettability, enabling stable free surface flow under magnetic fields, advancing liquid metal PFCs in nuclear fusion.

Contribution

The paper presents a novel microstructured liquid metal surface with pre-filled microstructures (MIFILM) that improves wettability and stability of liquid metal flow on PFCs, even under strong magnetic fields.

Findings

MIFILM reduces contact angle from 140° to 20°.

Liquid metal spreads stably on MIFILM surface at low flow rates.

Flow accelerates under magnetic field when Stuart number N<1.

Abstract

Regarding the plasma facing components (PFCs) in nuclear fusion, liquid metal PFCs with stable free surface flow on PFC surface are considered a promising alternative. However, due to the poor wettability of liquid metal on most solid substrates and the complex magnetohydrodynamic (MHD), the realization of stable free surface flow on PFCs surface is challenging. In the present study, using the 3D printed methods, we developed a novel liquid metal PFC surface with MIcrostructures pre-FIlled by Liquid Metal (MIFILM) to realize a stable free liquid metal surface flow. The experimental results demonstrated that due to the existence of MIFILM, the apparent contact angle (ACA) of liquid metal changes from 140$^{\circ}$ to approximately 20$^{\circ}$, indicating a transition from hydrophobic to hydrophilic. When the liquid metal flows on the MIFILM substrate, it is found that the liquid metal can completely spread on the surface with a stable and orderly free surface, even at a low flow rate. Moreover, the liquid metal could exhibit sustained spreading properties on the MIFILM substrate under a strong transverse magnetic field (up to 1.6 T). Results indicate that the magnetic field induces limited MHD drag but also accelerates the flow via two-dimensional effects. When the Stuart number $N<1$, the flow accelerates and the film thickness decreases. For $N>1$, both flow velocity and film thickness gradually stabilize. Therefore, the present novel MIFILM can offer a good choice for liquid metal PFC substrates in nuclear fusion.