G1: The Confinement Gate
The first gate proves the plasma confines energy well enough to reach the design gain point of Q_sci 3.076.
What G1 proves
G1 is the confinement gate. It demonstrates that the plasma holds its thermal energy long enough, at the design current and field, to reach the target gain. Confinement is quantified by the energy confinement time and its scaling with plasma current, density, and heating power.
The operating point
The design point is Q_sci 3.076 at 85.0 MW fusion power, with 9.66 MA of plasma current in a negative-triangularity (delta -0.30) spherical configuration. G1 is passed when the plasma sustains the confinement required to hold that operating point long enough to produce the neutron flux the foundry needs.
Why negative triangularity matters here
The chosen delta of -0.30 is intended to manage edge behavior and heat exhaust while preserving core confinement. G1 tests whether the predicted confinement holds at the real triangularity and current, since edge and core physics interact in ways that simulation can only bound, not settle.
- Measured quantity: energy confinement time at design current and field
- Pass criterion: confinement sufficient to reach the Q_sci 3.076 operating point
- Registered prediction: confinement time and its uncertainty band, filed before the test
Honest limits
Confinement scaling is the least certain part of any tokamak design. G1 is placed first because it carries the most physics risk. Until G1 is passed on the built machine, Q_sci 3.076 is a design and simulation value, and the program says so.