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Proton-boron fuel requires implosion to burn. In order to build a correct model of the implosion process driven by a high energy laser, we need to understand the material properties and behaviour of the boron fuel under extreme pressures and temperatures. This is no simple task as we’re talking about millions of times atmospheric pressure and millions to billions of Kelvins (degrees), occurring after petawatts (1,000 trillion watts) of energy have passed through fuel no bigger than a millimetre in size.

This topic is called ‘The Equation of State’ and was part of HB11 Energy’s Collaborative Science Program in April 2024. Scientists from HB11 Energy joined others from the University of Bordeaux (France), the Institute of Plasma Physics and Laser Microfusion (Poland), GSI Helmholtz Research Center (Germany), the Hellenic Mediterranean University (Greece) and the Soreq Nuclear Research Center (Israel), to participate in two experiments that were successfully finalised at the PALS laser facility in Prague, Czech Republic.

The aim of these experiments was to first prepare a platform to measure the Equation of State of materials in extreme conditions, obtained by laser-driven shock waves, and the study the Equation of State of boron nitride (BN) specifically.

The platform prepared employed diagnostics including Streak Optical Pyrometry, Velocity Interferometer System for Any Reflector and Photonic Doppler Velocimetry. The platform was then applied to study the Equation of State of boron nitride (BN) in the Megabar pressure range. This material is interesting as a target material for proton boron fusion, but also, due to its mechanical and thermodynamical properties, it could be used as a candidate to replace synthetic diamond as an ablator for inertial confinement fusion targets. Boron nitride features the hardness of diamonds and a high tensile strength, and is therefore a good candidate for a thinner ablator to support higher implosion pressures.

Note: a few participants in these experiments benefited from the financial support of the European Union COST Action PROBONO (PROton BOron Nuclear fusion: from energy production to medical applications).