Fusion Cross-Section

A measure of how likely two nuclei are to fuse at a given energy.

The fusion cross-section quantifies the probability that a collision at a given energy results in fusion. D–T has the largest cross-section at the lowest energy, which is why it is the easiest fuel; D–³He peaks higher, demanding the burner's 90 keV operation.

The cross-section's steep energy dependence is why fuel choice dominates machine design: D–T's large, low-energy peak makes it the easiest fuel and sets the breeder's modest temperature, while D–³He's higher-energy peak forces the burner to run far hotter. Everything downstream — confinement, heating, materials — follows from that curve.