Solution-processed flexible neutron converter foils

The cost increase of helium-3 has sparked the development of alternative thermal neutron detection technologies, specifically the use of boron carbide converters is one of the pillars of next-generation detectors. While the state-of-the-art sputter-coating technique produces high-quality films, it is limited in deposition area, and requires costly and energy-intensive vacuum processing. Lithium fluoride can reach a similar performance to boron carbide, yet requiring thicker layers. The field of functional printing offers several advantages to improve cost efficiency: deposition possibilities over large areas, a larger palette of materials and mechanically flexible substrates. We investigated the deposition of boron carbide and lithium fluoride materials via bar coating to fabricate high-performance neutron-sensing flexible films. After establishing a theoretical model for detection efficiency, fabrication processes were successfully established, film properties characterized and their outgassing evaluated. Mechanically flexible coatings of boron carbide and lithium fluoride films were produced with layer heights between 2 µm and 50 µm and binder concentrations between 10 % and 30 % by weight. They show encouraging results in terms of performance and mechanical stability. Due to the industrial readiness of printing technologies we expect a potential pathway towards developing a new generation of neutron converter foils to support the development of state-of-the-art large-area instruments. Lower costs, more detectors, better research.