Comparison of edge pedestal parameters for JT-60U and DIII-D H-mode plasmas

Abstract

Edge pedestal parameters (pedestal temperature and density, pedestal width)for JT-60U and DIII-D are studied and compared. For the discharges used in thestudy,the JT-60U H-mode operation space is in the high edge ion temperature and low edge electron density region, whereas DIII-D discharges have higher edgeelectron density and lower electron temperature. The pedestal width scalinghas been studied separately in each machine. We tested these pedestal scalingsagainst each other using JT-60U ion temperature pedestal width data andDIII-D electron temperature pedestal width data. Three previous scalings forpedestal width (Δ∝ε0.5ρpi,Δ/R∝(ρpi/R)0.66,Δ/R∝(βpPED)0.4) are tested usingtemperature pedestal widths from bothmachines. The relations between pedestal width and dimensionless parametersare examined. We propose a new pedestal width scaling for Te and Ti based onthis study of the two machines. The new scaling includes normalized poloidalgyroradius and Greenwald density: Δ∝aρ*0.4nG*0.3κ-1.5. The result of the comparison ofthese scalings is that the new scaling and Δ/R∝(βpPED)0.4 are well fitted and thefitting errors are almost the same as experimental error. However, furtherstudy is necessary for scaling parameters.