Experiments that decoupled H mode plasma current and plasma density have been performed for the first time on the DIII-D tokamak by the application of divertor cryopumping. Deuterium ELMing H mode discharges were operated in the single null configuration with 6 MW of neutral beam injection. These steady state discharges were operated at 1.5 and 0.75 MA with density ranges of (4.0-8.3) × 1019 and (2.7-4.0) × 1019 m-3, respectively. Therefore, for the first time in a steady state DIII-D H mode, a factor of 2 range in Ip (ne) has been obtained at fixed ne (Ip). A power law dependence of ELMing thermal confinement was assumed, with the result that for a given magnetic field and a fixed power dependence, τth = 0.18Ip0.91±0.08ne0.18±0.09PL-0.5. If a linear dependence of τ th on internal inductance is assumed the density dependence disappears. A local power balance analysis employing the 1½-D ONETWO transport code found that the one fluid effective diffusivity did not change with a factor of 2 change in density and was strongly reduced with increasing current. The reduction with increasing current occurs most dramatically for ρ > 0.5. Utilizing ONETWO for particle transport analysis demonstrated that the core particle transport was more rapid at lower density
Scaling of energy confinement time in the Globus-M spherical tokamak