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Accepted · first revision · record

Title: Why heavier hydrogen isotopes confine better than theory predicts
Plain: Simple turbulence theory says heavier fuel ions should leak heat faster, yet in experiments deuterium and tritium plasmas confine heat better than hydrogen. The reason has to be known to extrapolate to deuterium-tritium reactors.
Precise: Local gyro-Bohm scaling predicts energy confinement time $\tau_E$ proportional to A^-0.5 ($A=\text{ion mass number}$), while experiments find tau_E increasing with A, more strongly in H-mode. Identify the mechanism (E x B shear, collisional electron dynamics, pedestal dependence, zonal flows) and predict the D-T to D confinement ratio for ITER to within 15 percent.
Settled by: Multiscale gyrokinetic and pedestal modeling that reproduces measured H, D and D-T confinement on JET and another device.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: partially-resolved
Status note: JET D-T campaigns (2021-2023) confirmed better confinement in D-T than D; no single mechanism is accepted.
Posed since: (empty)