Physics
Nuclear Fusion
Two light nuclei repel each other fiercely, and only by slamming them together hard enough to tunnel through that wall do they merge and pour out energy. Every star and every reactor lives or dies on one line: whether the power out beats the power leaking away.
The box is a portrait, not a headcount; the reactivity, the power balance and the Lawson line are computed from the numbers you dial
Fusion power—
—
Scenario
Fuel
coolhot
thinstellar
leakytrapped
Numbers
Temperature—
Reactivity ⟨σv⟩—
Fusion power—
Wait per nucleus—
State—
What to observe
- In cold gas two positive nuclei turn back long before they touch. Heat it and a few tunnel through the barrier: flashes start, and the reactivity curve climbs almost vertically with temperature.
- In the Tokamak the triple product n·T·τ crosses the Lawson line and the alphas outheat every loss: ignited. Drop the confinement time and it dies, though the fuel never changed.
- Keep the tokamak but burn D-D: the fusion power falls more than a hundredfold and bremsstrahlung beats the self-heating. D-T is the easiest fuel there is.
- The Sun is only 15 million degrees, and a proton there waitsbillions of years to fuse. It shines because it is enormous and gravity holds it, not because it burns hard.
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