"Recent Advances in the Understanding of ELM suppression by Resonant Magnetic Perturbations on DIII-D,"Raffi Nazikian (Princeton Plasma Physics Laboratory and DIII-D)

Date: 
Thursday, February 27, 2014 - 1:00pm to 2:30pm
Series: 
Plasma Seminars

Plasma Seminar

Thursday, February 27
1-2:30PM
Physics and Astronomy Building (PAB) Room 4-330

Guest Speaker: Raffi Nazikian (Princeton Plasma Physics Laboratory and DIII-D)

Talk Title: "Recent Advances in the Understanding of ELM suppression by Resonant Magnetic Perturbations on DIII-D"

Abstract:

Edge Localized Modes (ELMs) can deposit up to 20% of the stored energy in the plasma to the walls of a fusion reactor. ITER cannot withstand too many large amplitude ELMs due to the potential erosion of the metal wall with up to 20 MJ of energy loss predicted per ELM event. Externally applied Resonant Magnetic Perturbations (RMPs) in ITER-like plasmas on DIII-D are known to suppress ELMs by enhancing thermal transport at the top of the H-mode pedestal, but the physics mechanism(s) of the enhanced thermal and particle transport leading to ELM suppression remains elusive. Advances in MHD simulations indicate that island formation may play a role in ELM suppression by enhancing transport at the top of the pedestal and limiting the expansion of the pedestal to an unstable width. While direct imaging of islands in ELM suppressed plasmas remains elusive, a series of recent measurements provide indirect evidence of island formation. On the other hand, an alternative model of ELM suppression known as the flutter model also predicts enhanced transport induced by RMPs but without the need for islands. Distinguishing between these two mechanisms is of critical importance to ITER because the physics conditions required for island formation at the top of the pedestal are quite restrictive and may not translate to ITER conditions. Progress in the understanding of the plasma response to RMPs and the resulting transport modifications leading to ELM suppression will be discussed.