Investigation of Liquid Metal Ion Sources based on Magnetic Suspensions

• Applicant: Professor Dr. Martin Tajmar
• Subject Area: Fluid Mechanics ; Synthesis and Properties of Functional Materials
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 543815948

Liquid metal ion sources are used in space applications in the form of ion thrusters, as well as in terrestrial applications such as focussed ion beam systems for surface microstructuring. The generation of the ions is based on field evaporation, in which evaporating atoms of a liquid metal are ionized under the influence of a high electric field. Sufficiently high electric field strengths (10^7 V/m) are achieved by geometric field enhancement with the aid of very fine, usually needle- or capillary-shaped electrode structures, so that ion currents in the microampere range can be made available with one individual needle. The needle structures, which are made of tungsten, are the key element of liquid metal ion sources because their fabrication is complex and costly, and they degrade during operation due to various effects such as ion sputtering or solubility in the liquid metal. They also limit the scalability of achievable ion currents, as their clusterability is severely limited using current fabrication methods. However, high thrusts and thus high emission currents are desirable, especially in space propulsion systems. The present research project aims to develop a new type of liquid metal ion source based on magnetized liquid metals that spontaneously form needle structures under the influence of an external magnetic field. These liquid metal needles would not require a complex support structure, could have the ability to self-heal, and would be highly scalable, making them suitable for generating high emission currents for terrestrial and space applications with a much more compact design.

• DFG Programme: Research Grants