L-H transition Plasma confinement degrades as the applied heating power is increased (referred to as the low-confinement mode, or the L-mode). Above a critical power threshold that crosses the plasma boundary, the plasma transitions to H-mode where the confinement time approximately doubles.
Edge transport barrier In the H-mode, an edge transport barrier forms where
turbulent transport is reduced and the pressure gradient is increased.
Edge-localized modes The steep pressure gradients in the edge pedestal region leads to a new type of
magnetohydrodynamic instability called the
edge-localized modes (ELMs), which appear as fast periodic bursts of particle and energy in the plasma edge.
Energy confinement scaling is the foreseen operating regime for most future tokamak reactor designs. The physics basis of
ITER rely on the empirical ELMy H-mode energy confinement time scaling. One such scaling named IPB98(y,2) reads: : \tau_{E}^{\text{IPB98(y,2)}}=0.0562 M^{0.19} I_{\text{P}}^{0.93} R^{1.97} \epsilon^{0.58} \kappa^{0.78} n^{0.41} B^{0.15} P^{-0.69} where • M is the hydrogen isotopic mass number • I_{\text{P}} is the plasma current in \text{MA} • R is the major radius in \text{m} • \epsilon is the inverse aspect ratio • \kappa is the plasma elongation • n is the line-averaged plasma density in 10^{19} \text{m}^{-3} • B is the toroidal magnetic field in \text{T} • P is the total heating power in \text{MW} ==References==