Scaling of H-mode Pedestal and ELM Characteristics With Gyroradius

The dependence of the H-mode pedestal structure and ELMs on gyroradius ($\rho^* = \rho/a$) was examined in experiments combining data from the JET and DIII-D to produce a factor of 4 variation in $\rho^*$, while keeping the plasma shape, $q$, normalized pressure ($\beta$), collisionality, Mach number, and $T_i/T_e$ at the pedestal top constant. In this scan, the width of the steep gradient region of $T_e$ and $n_e$, $\Delta$, was independent of $\rho^*$ within uncertainties, $\Delta/a\sim (\rho^*)^{0.0\pm 0.15}$. The pedestal pressures and widths were in quantitative agreement with the EPED1 model in which the pedestal structure is set by combining the peeling-ballooning and kinetic ballooning stability thresholds. The ELM energy loss normalized to the pedestal energy decreased from 40\% to 10\% as $\rho^*$ decreased by a factor of 2 in DIII-D, but the trend did not continue in smaller $\rho^*$ on JET.