Ion collisionality and L--H transition in tokamaks

When the previous H-mode theory [K. C. Shaing and E. C. Crume, Jr., Phys. Rev. Lett. 63, 2369 (1989)] is extended to include a bi-Maxwellian ion distribution with both cold and hot ion components to model the effects of the non-Maxwellian distribution, the collisionality of the cold ions ν*ic becomes an irrelevant bifurcation parameter, as it is for the electrode-induced H mode. Thus, the observation that the L--H transition can occur even when ν*ic much-gt 1 is consistent with the fundamental physics of the ion orbit loss model, including a hot ion component