#4717 Smallest Theoretical Volume for Self-Sustaining Fusion Reaction
#4717 Smallest Theoretical Volume for Self-Sustaining Fusion Reaction #4717 Theoretically, what is the smallest volume for a self-sustaining fusion reaction (assuming fuel is added as needed)? A continuous, self-sustaining (ignited) fusion reaction requires that the heating power from charged fusion products—principally the 3.5 MeV alpha -particles in a Deuterium-Tritium (D-T) reaction—exceeds all energy loss channels (radiation and transport) without relying on external input power. Because theoretical minimum volume depends entirely on how the plasma is confined and how dense it is, the limits fall into three distinct physical regimes: Confinement Regime Typical Density (n) Confinement Time (τE) Theoretical Minimum Volume Pulsed Inertial (ICF) sim 10^25 - 10^26 cm^-3 sim 10 - 100 ps sim 10^-6 cm^3 (sub-millimeter) Ultra-High Magnetic Field ( $B \sim 20\text{--}30\text{ T}$ ) sim 10^14 - 10^15 cm^-3 sim 0.5 - 2 s sim 10--50 m^3 Conventional Magnetic (Tokamak/Stellarator)...