Predict-first experiments and modeling of perturbative cold pulses in the DIII-D tokamak

Abstract

Cold pulses are introduced in Ohmic DIII-D tokamak plasmas, revealing for the first time in this machine a quick increase of core electron temperature shortly after the edge cold-pulse injection at low collisionality.The experimental results are consistent with predict-first simulations enabled by the Trapped Gyro-Landau-Fluid (TGLF) transport model. Measurements of electron density evolution during the cold-pulse propagation are enabled by a high time resolution density profile reflectometer. The density evolution reveals the quick propagation of a pulse from edge to core, which is a mechanism to transiently increase core temperature in low-collisionality plasmas. Local transport simulations with measured density evolution demonstrate that the core temperature response can indeed be explained by the stabilization of Trapped Electron Mode (TEM) turbulence at low collisionality, thus providing confidence that local transport modeling is enough to explain cold-pulse propagation and associated phenomenology.

The local nature of the plasma response to cold pulses with electron and ion heating at ASDEX Upgrade

“…A current study on DIII-D [22] confirms the results obtained on C-Mod. It demonstrates that in low density OH plasmas the rapid density flattening produced by the laser ablation and measured by reflectometry is indeed compatible with the electron heat transport reduction which is required by TGLF to obtain the central temperature increase which is experimentally observed.…”

Prompt core confinement improvement across the L–H transition in DIII-D: Profile stiffness, turbulence dynamics, and isotope effect

“…Then, the transport suppression front propagates inwards in a chain reaction manner. Rapid decrease of the n e gradient possibly plays a role through an off-diagonal contribution as well, as demonstrated in [23,24] for the nonlocal transport study. After the prompt reduction in q e /n e ceases at t − t LH = 1.3 ms, the trajectory in the fluxgradient diagram transits to a different branch with χ HP e ∼ χ PB e , i.e., no stiffness.…”

Predictions of core plasma performance for the SPARC tokamak

“…2019; Rodriguez-Fernandez et al. 2019; Luda et al. 2020), and database studies have suggested that physics-based models of heating and transport perform equally as well as, if not better than, empirical scalings in predicting performance in present devices.…”