Dartmouth Events

Abstract: A long-standing enigma in plasma transport is studied by modeling of cold-pulse experiments conducted on the Alcator C-Mod and DIII-D tokamaks.  Controlled edge cooling of fusion plasmas triggers core electron temperature increases on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. A new integrated modeling tool that leverages the new trapped gyro-landau fluid transport (TGLF) model that includes multi-scale physics has been used to interpret data from C-Mod  and develop predictions for new experiments at DIII-D. The interpretive analysis at C-Mod shows that the steady-state profiles, the cold-pulse rise time, and the disappearance at higher density measured in these experiments are well matched by the new TGLF model. This provides new evidence that the existence of nonlocal transport phenomena is not necessary for explaining cold-pulse experiments in tokamak plasmas. Predictive analysis is used to design a new experiment to leverage the new Laser Blow-Off (LBO) system at DIII-D, to test whether or not cold pulse inversion will occur on DIII-D, and if it does occur, to test whether the model can accurately predict the plasma conditions where it occurs. Detailed interpretive and predictive analysis from the C-Mod and DIII-D tokamaks will be presented, to make the case that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.