Is any ELM-free or small-ELM regime compatible with reactor conditions
In plain words
Several tokamak operating modes keep good confinement without large ELM bursts, but each has been found only under conditions that a reactor may not reach. Whether any of them survives at reactor density, low rotation and a cool divertor is unknown.
Precise statement
Candidate regimes are QH-mode (edge harmonic oscillation), I-mode, EDA H-mode, small or grassy ELM regimes (quasi-continuous exhaust) and negative-triangularity L-mode edges. Determine whether at least one achieves $H_{98}$ near 1, no type-I ELMs and a detached divertor simultaneously at reactor-relevant $n_{e}/n_{G}$ of about 0.8 or more, low external torque, high separatrix density and pedestal collisionality as low as ITER $Q = 10$. An answer is a demonstrated discharge meeting all conditions on one device, or a validated stability analysis showing that each regime's access window excludes them.
What would settle it
A steady discharge meeting all listed conditions simultaneously, together with a validated model of its access window extrapolated to ITER.