This seminar will only take place online. Please contact [email protected] for the Zoom link.

Speaker: Brian A. Grierson, General Atomics

Title: “Advances in Measuring and Understanding Plasma Rotation in the DIII-D Tokamak”

Abstract: Plasma flow in the tokamak has an enormous influence on stability and confinement. Plasma rotation can be driven by auxiliary power systems that inject high energy neutral particle beams, but rotation and rotation shear can also be self-generated by turbulence when the plasma is heated. Characterizing and understanding this self-generated intrinsic plasma rotation is a challenge for both diagnosis and theoretical models. Advances in high temperature plasma diagnostics have enabled the routine, direct measurement of the flow of the fuel ions in the DIII-D tokamak, and we have used these measurements to characterize the plasma rotation and compare with simulations.  In this presentation, we will describe the measurement technique for determining the ion flow and intrinsic rotation phenomenology in the tokamak core, and also near the plasma boundary. Enabled by these new measurements, nonlinear gyrokinetic simulations of the core plasma have been tested by simulating the experimental plasma conditions, and reveal flows that compare remarkably well to the observations. Near the plasma boundary, a reduced theoretical model of plasma rotation has been developed and recently tested in the “high confinement” mode of tokamak operation, and also agrees remarkably well with these new measurements. Taken together, these advances in understanding plasma rotation increase our confidence in projecting to the rotation expected in future devices such as ITER, a large tokamak under construction in southern France. 

Bio: Brian A. Grierson is the Director of the Fusion Pilot Plant Design Hub at General Atomics in San Diego, CA. Prior to this new role Brian was a Principal Research Physicist and Division Head for the Princeton Plasma Physics Laboratory’s DIII-D Collaboration and head of the Edge & Boundary Physics Group at the DIII-D National Fusion Facility. His research specialities include tokamak transport, confinement, diagnostics, heating and current drive. In 2014 Brian was granted a DOE Early Career Research Program award for his proposal “Exploration of main-ion properties at the boundary of fusion reactors” to develop a main-ion charge-exchange diagnostic suitable for the H-mode pedestal and study the transport of particles, energy and momentum in the main-ion channel.