The ~90 keV Operating Point
The burner is designed to run near a 90 keV ion temperature, where the D–He-3 reactivity is high enough to be practical.
Where the reaction runs
The burner's design ion temperature is roughly 90 keV — about 1 billion kelvin. This is far hotter than a D–T machine, which ignites in the 10–20 keV range. The reason is the D–3He cross-section: both nuclei carry a positive charge of +1 and +2, so the Coulomb barrier is higher than for D–T, and useful reactivity only builds up at tens of keV.
Pushing higher than ~90 keV gives diminishing gains in reactivity while increasing radiation losses and confinement demands. Running much lower drops the reaction rate below what the power balance can sustain. The ~90 keV point is a compromise between reactivity, radiation losses, and what the tandem-mirror confinement can hold.
A demanding target
No device has sustained a D–3He plasma at this temperature and confinement in steady state. The plug operating regime required to hold such a plasma is one of the burner's honest gates: it sits well beyond the parameters any built mirror has reached.
The choice of ~90 keV is also a statement about what the confinement must deliver: hotter ions mean a higher pressure the magnetic well and plugs must hold, and a higher radiation load the power balance must overcome. The operating point is thus not just a plasma-physics number but the anchor that sets the field, the plug potential, and the engineering margins across the whole machine.
- Design ion temperature ~90 keV (~109 K)
- Set by the D–3He Coulomb barrier
- Balances reactivity against radiation losses
- No device has yet reached this regime steadily