Liquid metals (LMs) are compelling candidates for use as plasma facing components (PFCs) in fusion devices to mitigate heat loading, limit damage due to erosion, and possibly breed tritium. When used as electrodes, such as in z-pinch devices, PFCs are subject to large current and magnetic flux densities resulting in large Lorentz forces. Furthermore, if the PFCs are LM, the forces excite wave behavior that has not previously been investigated. The work presented here first characterizes the response of LMs to current pulses which peak between 50 and 200 kA and generate magnetic pressures between 0.5 and 5 MPa. High-speed videography records the liquid metal free surface during and after the current pulse and captures a fast moving, annular jet of LM emerging from the main body. The vertical velocities of the jet range from 0.6 to 5.3 m/s which is consistent with hydrodynamic predictions. Ejection of small droplets is observed from the LM immediately after the current pulse, preceding the LM jet, with velocities ranging from −3.1 to 18.9 m/s in the vertical direction and −14.3 to 6.3 m/s in the radial. A statistical model is developed to predict the likelihood of certain LM PFC material contaminating a core plasma and the severity in such an event. Lastly, effectiveness of bulk wave movement mitigation is investigated with two solid barrier designs, a cylindrical and conical baffle. These designs were fabricated after an iterative design process with assistance from hydrodynamic simulations. A cylindrical baffle design is shown to be preferable for integration into future fusion devices for the reduced likelihood of interference with plasma column formation. / Doctor of Philosophy / Liquid metals are considered for use as a coating on the interior surfaces in nuclear fusion reactors because they can remove heat, reduce damage, and generate additional fuel for the reactor. There has been very little research on what happens to the liquid metal when large amounts of electric current pass through it, as would be necessary in some designs. The work presented here first shows the liquid responds to large amounts of electric current with a fast moving, ring-shaped jet that correlates to the specific amount of current used. A theoretical relationship is used to relate the jet to hydrodynamic scenarios with solid bodies entering liquids. Small droplets are also observed sprayed from the LM earlier in time and the likelihood and severity of liquid metal contaminating the fusion core is analyzed. Finally, solid barriers are used to slow down the jet and minimize the mass it contains. To reduce the likelihood that the jet interferes with the fusion core, certain characteristics of barriers are identified as being preferable for use in plasma devices.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/117338 |
| Date | 10 January 2024 |
| Creators | Weber, Daniel Perry |
| Contributors | Aerospace and Ocean Engineering, Adams, Colin, Brizzolara, Stefano, Srinivasan, Bhuvana, Paterson, Eric G. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
Page generated in 0.002 seconds