L-H Transition Re-visited

W. W. Lee, Princeton Plasma Physics Laboratory: Despite of 40 plus years of research on the H-mode in the magnetic fusion community, there has been no consensus as to the physics origin. In this presentation, we will review the exiting theories and most recent experiments on the various machines [1,2]. We believe the most plausible theoretical explanation comes from the work originated by Lee and White [3], which relates the L-H transition to the minimum energy state in tokamaks [3,4] through the Er field generated at the pedestal by the finite Larmor radius effects due the sharp pressure gradient.

[1] H. K. Park, “Evolution of Energy Confinement Physics,” private communications (2025).

[2] G. J. Kramer, A. Bortolon, A. Diallo and R. Maingi, Nucl. Fusion 64, 106035 (2024).

[3] W. W. Lee and R. B. White, Phys. Plasmas 26, 040701 (2019).

[4]. M. J. Hole, S. R. Hudson and R. L. Dewar, J. Plasma Physics 72, 1167 (2006).