Precision manufacturing of Faraday screens for long pulse neutral beam injectors

Controlled thermonuclear fusion promises to radically transform our society by providing a nearly limitless form of renewable energy. Magnetic confinement fusion sources require a powerful neutral beam injector (NBI) to heat the plasma using a highly energetic neutral beam. With ITER already under construction and recent surge in commercial fusion startups, the U.S. has begun an accelerated path towards construction of a Fusion Pilot Plant (FPP). During steady state NBI operation as needed in FPP, Faraday Screens with active water cooling are required such that the ion source can sustain the NBI for extended periods. In this project, RadiaBeam proposes to develop, fabricate and test a modular, actively cooled Faraday screen for steady state neutral beam operation in collaboration with Prof Florian Laggner of North Carolina State University. These roughly 20cm diameter by 15cm long thin-walled shields will leverage RadiaBeams’ extensive linear accelerator capabilities including RF modelling; clean, vacuum compatible manufacturing and in-house high-power testing. In Phase I, we will develop a multiphysics model for our Faraday screen including thermal, mechanical, plasma and RF requirements. We will investigate various fabrication methods and materials for active cooling of the Faraday screen, including vacuum brazing, electron beam welding and additive manufacturing. We will also develop a molybdenum coating process and fabricate of 4” diameter, proof of principle assembly. This component will be tested at North Carolina State University with support from Prof. Laggner using commercially available induction heating coils. Fusion power plants need to be a reliable source of electricity generation. Since fusion is principally still a research project, the associated supply chains are not well established. Cross-cutting technology can reduce the burden of the fusion research community to carry out all technology maturation. RadiaBeam currently has extensive, company-wide experience with high power, copper RF linear accelerators, as well as a vacuum-first, quality mindset making the potential cross-over applications to fusion components relatively easy. Considering RadiaBeam’s expertise in RF linear accelerator design, fabrication and testing; we are confident that this project can provide the steppingstone towards becoming a physics-focused fusion component supplier.