Evaluation of a boron nitride–boron pebble aggregate material for renewable plasma-facing surfaces in magnetic fusion devices

We demonstrate a new renewable boron aggregate material that can withstand heat loads of 40 MW m^-2 without cooling and featuring low sublimation of below 100 Torr-L/s/m² and sputtering yield of 0.04 from 40 eV D, similar to solid boron. The retention of deuterium (D) is 3.2 × 10²⁰ D/m², 200$\times$ less than solid boron, 100$\times$ less than carbon, and comparable to tungsten at similar fluence and energy. The material sheds under high heat loads, at a rate of 0.35 cm/s, exposing the cool surface to the plasma, allowing heat removal and tritium extraction away from the plasma and eliminating the need for cooling channels. This recession rate can be compensated for, as the material can be extruded from a paste at a rate of 1 cm/s.