Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

Abstract

A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. This Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.

Predictions of core plasma performance for the SPARC tokamak

“…2018; Rodriguez-Fernandez et al. 2018; Angioni et al. 2019; White 2019) have allowed physic-based simulations to also inform the design of SPARC during the early stages of its development.…”

Validation of nonlinear gyrokinetic transport models using turbulence measurements

“…The standard models of drift-wave turbulent transport are being extended to include the interactions between MHD modes and turbulence (McDevitt & Diamond 2006;Militello et al 2008;Bañón Navarro et al 2017) and the interactions between fast ion modes and turbulence (Estrada Mila et al 2006;Pueschel et al 2012;Wilkie et al 2016). Most exciting perhaps, there are experimental observations that can be viewed as grand challenges to the standard turbulent-transport models, including intrinsic rotation and intrinsic rotation reversals (Parra & Barnes 2015;Rice 2016), momentum transport (Diamond et al 2013) and 'non-local' perturbative transport phenomena (Ida et al 2015;Rodriguez-Fernandez et al 2018a). These areas are described briefly in the next four subsections.…”

Transient Electron Thermal Transport Analysis Accounting Oblique Electron Cyclotron Resonance Heating Injection to Magnetic Field Line

“…It is believed that the heat flux in magnetically confined high temperature plasmas cannot be expressed by the simplest "Fick's law", where the heat flux is modeled to be proportional to the local temperature gradient [1]. Instead, a wide variety of models, including the diffusion-convection model [2][3][4][5], the critical gradient model [6,7], nonlocal models [8][9][10][11][12][13][14], models including off-diagonal contribution [15][16][17], and others were developed for comprehensively describing the complicated transport phenomena.…”