Self-Heating Fusion Driven by a Detonation Cycle in an Mg–CO₂ System

In previous peer-reviewed work presented at ASME-POWER 2024, the author reported that a reaction system composed of a magnesium spherical shell and carbon dioxide can potentially satisfy the Lawson criterion without external heating. This result demonstrated, for the first time, that the Mg–CO₂ reaction system can intrinsically form the conditions required for fusion heating and compression. Building on this finding, the present study systematically organizes the underlying physical and chemical mechanisms and proposes a new fusion concept termed MgFusion. MgFusion fundamentally differs from conventional fusion approaches in that a chemically driven detonation cycle in the magnesium–carbon dioxide (Mg–CO₂) system is employed as the primary source of pressure and heating. Under geometrically confined conditions, the strongly exothermic Mg–CO₂ reaction exhibits detonation behavior and generates shock waves. These shock waves directly compress and heat a small amount of fusion fuel enclosed within a magnesium spherical shell, without the use of external lasers, magnetic fields, or particle beams. A model system consisting of a magnesium spherical shell with an outer diameter of approximately 10 mm and an inner diameter of 2 mm is examined. The shell contains approximately 0.9 g of magnesium, releasing on the order of 16 kJ of chemical reaction energy, while enclosing only ~100 μg of fusion fuel (D–T or p–B¹¹). This clear separation between the heating medium and the fusion fuel suppresses fuel loss during the heating process. In this configuration, the fusion fuel is physically shielded by the high-density metallic shell, which significantly suppresses the free-electron density. As a result, energy losses due to bremsstrahlung radiation are effectively limited. Furthermore, because compression is uniformly driven by shock waves generated by a mass-bearing magnesium shell rather than by ablation, the Rayleigh–Taylor instability—one of the dominant limiting factors in laser-driven inertial confinement fusion—is structurally mitigated. Analysis based on the Lawson criterion suggests that this approach can simultaneously achieve high density, high temperature, and extended confinement time, potentially satisfying ignition conditions not only for D–T fusion but also for advanced p–B¹¹ fusion, which requires substantially higher temperatures. The role of carbon dioxide differs fundamentally before and after the fusion event. Before fusion, carbon dioxide thermally interacts with the magnesium combustion products generated during the detonation phase, primarily magnesium oxide (MgO) and carbon (C), enabling effective recovery and reutilization of chemical reaction heat. After fusion, high-energy helium particles are produced and decelerated through energy transfer to the surrounding carbon dioxide, which absorbs and disperses the fusion-product energy. As a result, the extracted energy is converted into thermal energy of carbon dioxide gas at approximately 1200 °C, allowing practical heat recovery without requiring ultra-refractory structural materials. In this way, MgFusion establishes a new paradigm of self-heating fusion in which fusion conditions are driven directly by pressure generated through chemical reactions. Owing to its ultra-compact structure, extended effective confinement time, and integrated utilization of carbon dioxide with simultaneous carbon fixation, MgFusion opens a research domain that is fundamentally distinct from conventional fusion research frameworks.