171. SYNTHETIC DIAGNOSTICS OF PLASMA TURBULENCE MODEL WITH APPLICATION TO MAGNETIC CONTROLLED FUSION
Name: Payam Vaezi
Grad Year: 2017
Turbulence is a ubiquitous phenomenon in fluids that has been recognized and studied for a long time. It is often called the last unsolved problem in classical physics, mainly because we cannot predict in detail how or why turbulence occurs or fully predict its behavior. However, it is extremely important to gain an understanding of it in laboratory plasmas and magnetically confined fusion devices because it causes increased particle and energy transport. For instance, very good particle confinement is needed in Tokamak scrape-off-layer but not in the core. Better understanding of plasma turbulence leads to better prediction of future devices performance. At the moment, most of our knowledge gained in fusion experiment is based on assumption that diagnostics are accurate enough to successfully interpret the results. Motivated by better understanding of turbulence dynamics, we have used the Controlled Shear Decorrelation Experiment (CSDX) linear plasma device at UCSD which provides a simple system for nonlinear studies of coupled drift-wave turbulence/zonal flow dynamics, and does not have complexities of large toroidal Tokamaks. We present numerical simulations of a minimal model of 3D collisional drift-wave physics in CSDX which evolves density, vorticity and electron temperature perturbations, with proper sheath boundaries conditions. Synthetic diagnostics -virtually measuring plasma quantities of simulation through experimental techniques- such as synthetic Langmuir probes and synthetic camera imaging have been applied to validate the code against experimental measurements, producing a rich basis of comparison. Interestingly, we can observe from the results that some synthetic plasma quantities such as particle flux measured experimentally may differ from real particle flux, while validating experimental measurements. Understanding the missing link between link between computational theoretical models and experimental measurements in magnetically confined devices can immensely increase our interpretation of results. The validation of plasma-turbulence codes plays a fundamental role in the development of magnetically confined fusion, as it is a key step in assessing the maturity of our understanding of the plasma dynamics and the predictive capabilities of simulations, ultimately leading to better and efficient design of future fusion devices.
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