17th Workshop on MHD Stability Control: addressing the disruption challenge for ITER

Abstract

This annual workshop on magnetohydrodynamic stability control was held on 5–7 November 2012 at Columbia University in the city of New York, in the aftermath of a violent hydrodynamic instability event termed ‘Hurricane Sandy’. Despite these challenging circumstances, Columbia University managed an excellent meeting, enabling the full participation of the community. This Workshop has been held since 1996 to help in the development of understanding and control of magnetohydrodynamic (MHD) instabilities for future fusion reactors. It covers a wide range of stability topics—from disruptions, to tearing modes, error fields, edge-localized modes (ELMs), resistive wall modes (RWMs) and ideal MHD—spanning many device types (tokamaks, stellarators and reversed field pinches) to identify commonalities in the physics and a means of control.The theme for 2012 was ‘addressing the disruption challenge for ITER’, and thus the first day had a heavy focus on both the avoidance and mitigation of disruptions in ITER. Key elements included understanding how to apply 3D fields to maintain stability, as well as managing the disruption process itself through mitigating loads in the thermal quench and handling so called ‘runaway electrons’. This culminated in a panel discussion on the disruption mitigation strategy for ITER, which noted that heat load asymmetries during the thermal quench appear to be an artifact of MHD processes, and that runaway electron generation may be inevitable, suggesting research should focus on control and dissipation of the runaway beam.The workshop was combined this year with the annual US–Japan MHD Workshop, with a special section looking more deeply at ‘Fundamentals of 3D Perturbed Equilibrium Control’, with interesting sessions on 3D equilibrium reconstruction, RWM physics, novel control concepts such as non-magnetic sensing, adaptive control, q < 2 tokamak operation, and the effects of flow. The final day turned to tearing mode interactions, exploring the state of the art in 3D modeling, and innovative means of control through application of electromagnetic torques, use of electron cyclotron current drive and even the idea of electrostatic current drive. This concluded with a second panel discussion on the disruption avoidance strategy in ITER, which commented on the important role played by energetic particles in stability, ideas of active stability sensing and ways to progress 3D reconstruction.In this special section of Plasma Physics and Controlled Fusion , we present several of the invited and contributed papers from the 2012 workshop, which have been subject to the normal refereeing procedures of the journal. These give a sense of the exceptional quality of the presentations at this workshop, which may be found at: http://fusion.gat.com/conferences/mhd12/.The Program Committee deeply appreciates the participation and support our community continues to show in this workshop, which provides an unparalleled opportunity for in-depth discussion of MHD issues. We would also like to thank our hosts Columbia University, and in particular Professor Gerald Navratil, for outstanding support and facilities in the face of Hurricane Sandy's adversity. The meeting thanked outgoing Program Chair, Dr Richard Buttery from General Atomics, and welcomed next year's Program Chair, Professor David Maurer from Auburn University. The next meeting will be held in Santa Fe 18–20 November 2013.