Woodruff School of Mechanical Engineering

NRE 8011/8012 and MP 6011/6012 Seminar

Nuclear & Radiological Engineering and Medical Physics Programs


Evolution of Edge Pedestal Transport Between ELMs in DIII-D


Dr. John-Patrick Floyd


Georgia Tech


Thursday, November 6, 2014 at 11:00:00 AM


Boggs Building, Room 3-47


Dr. Weston Stacey


Edge-Localized Modes (ELMs) are cyclical instabilities characteristically found in tokamak plasmas operating in High-Confinement Mode (H-mode). ELMs have the potential to damage reactor components due to the energy the carry from the plasma to the plasma-facing components (PFCs). At the high performance levels expected from ITER and other future tokamak devices, the energy contained in ELMs will exceed the heat capacities of the PFCs, and they must not be allowed to occur. The research that will be presented is a part of the ELM mitigation and suppression efforts that are a major priority in the fusion research community. It also contributes to an improved understanding of H-mode edge pedestal transport, which is related to overall plasma performance.

Evolution of measured profiles of densities, temperatures and velocities in the edge pedestal region between successive ELM events are analyzed and interpreted in terms of the constraints imposed by particle, momentum and energy balance. In order to gain insights regarding the underlying evolution of edge transport processes between ELMs, the variation of diffusive and non-diffusive (pinch) particle, momentum, and energy transport over the inter-ELM period are examined for four plasma discharges. Experimental data from operation of the DIII-D tokamak at General Atomics was utilized for this research, and the discharges have plasma currents from 0.5 to 1.5 MA, and inter-ELM periods from 50 to 220 ms. The results of the research, which compare and contrast diffusive and non-diffusive transport in the edge along with existing drivers, will be summarized, and the implications for ELM control discussed.


John-Patrick Floyd earned his PhD, MS, and BS in Nuclear and Radiological Engineering from Georgia Tech, and also a MS in International Affairs. His main research interest in Nuclear Engineering is fusion plasma physics, and he is a member of the Boundary and Pedestal Group of the National DIII-D Experimental Science Team. His work focuses on contributing to an improved understanding of the H-mode edge pedestal and inter-ELM evolution of pedestal transport through interpretive analyses of experimental data.

John-Patrick also enjoys nuclear systems engineering projects, and has contributed to the design and detailed revision of the SABR fusion-fission hybrid subcritical burner reactor design concept. In the field of International Affairs, John-Patrick specializes in the study of energy and emerging technology policy, with additional interests in the related fields of nuclear nonproliferation policy and security technology.