Edge dimensionless identity experiment on DIII-D and alcator C-Mod

Experiments were carried out to study the similarity of H-mode (high confinement mode) physics on the Alcator C-Mod [I. H. Hutchinson , Phys. Plasmas 1, 1511 (1994)] and DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] tokamaks comparing plasmas with matched local edge dimensionless parameters (beta, rho*, nu*, q(95)) and shape (epsilon, kappa, delta). It was observed that matching local values of the dimensionless parameters on top of the H-mode pedestals produces similar T-e and n(e) profiles across the entire pedestal region, with pedestal width scaling linearly with the machine size. Furthermore, in H-modes with matched pedestals, similar edge fluctuations were observed. Discharges in DIII-D with scaled pedestal parameters similar to those of C-Mod EDA (enhanced D-alpha) H-mode showed a quasicoherent mode localized to the outer half of the pedestal, similar to the C-Mod quasicoherent mode (QC mode). The wavenumber of the mode observed on DIII-D matches the wavenumber of the C-Mod QC mode if scaled with the machine size. For higher pedestal temperatures and pressures, small high frequency edge localized modes appear in both machines. (C) 2003 American Institute of Physics.