The 13th International Workshop on H-mode Physics and Transport Barriers (Oxford, UK, 2011)
Authors: Saibene G. 
Published: October 2012

The 13th International Workshop on H-mode Physics and Transport Barriers, held in Lady Margaret Hall College in Oxford in October 2011 continues the tradition of bi-annual international meetings dedicated to the study of transport barriers in fusion plasmas. The first meeting of this series took place in S Diego (CA, US) in 1987, and since then scientists in the fusion community studying the formation and effects of transport barriers in plasmas have been meeting at this small workshop to discuss progress, new experimental evidence and related theoretical studies.
The first workshops were strongly focussed on the characterization and understanding of the H-mode plasma, discovered in ASDEX in 1982. Tokamaks throughout the entire world were able to reproduce the H-mode transition in the following few years and since then the H-mode has been recognised as a pervasive physics feature of toroidally confined plasmas. Increased physics understanding of the H-mode transition and of the properties of H-mode plasmas, together with extensive development of diagnostic capabilities for the plasma edge, led to the development of edge transport barrier studies and theory. The H-mode Workshop reflected this extension in interest, with more and more contributions discussing the phenomenology of edge transport barriers and instabilities (ELMs), L–H transition and edge transport barrier formation theory. In the last 15 years, in response to the development of fusion plasma studies, the scientific scope of the workshop has been broadened to include experimental and theoretical studies of both edge and internal transport barriers, including formation and sustainment of transport barriers for different transport channels (energy, particle and momentum).
The 13th H-mode Workshop was organized around six leading topics, and, as customary for this workshop, a lead speaker was selected for each topic to present to the audience the state-of-the-art, new understanding and open issues, as well as to stimulate and lead the open discussion. Poster sessions were also organized to present specialist papers and provide a venue for continued discussion. The topics selected for this edition of the workshop were:

1. Integrated plasma scenarios for ITER and a reactor: experimental and theoretical studies, including the self-stabilizing transport approach.

2. Edge transport barrier control and plasma performance: physics of 3D stochastic magnetic fields for ELM suppression.

3. H-mode transition physics and H-mode pedestal structure: pedestal dynamics near transitions and requirements for high-confinement access and sustainment.

4. Energetic particle driven instabilities and related physics: H-mode and the transport barrier.

5. Role of and evidence for non-diffusive particle and toroidal momentum transport and impact of fuelling: experiments, theory and modelling.

6. Long-range correlation of plasma turbulence and interaction between edge and core transport.

The choice of topics, and the amount of progress in the understanding of the complexity of transport barriers physics reflect the drive in the fusion community towards the preparation for the ITER tokamak operation.
More than 100 scientists (including students) attended the three-day workshop, coming from all over the world to present their newest results, discuss with colleagues and enjoy the atmosphere of the beautiful Lady Margaret Hall.
The preparation work of the International Advisory Committee (G. Saibene (EU – Chair), R. Groebner (US), T. S Hahm (KO), A. Hubbard (US), K. Ida (Japan), S. Lebedev (RF), N. Oyama (Japan), E Wolfrum (EU)) has been rewarded by the enthusiastic participation of scientists, experimentalist, modellers and theoreticians, and by the high level of the scientific discussion throughout the workshop, during lunch breaks and even at the conference dinner. The Committee is also grateful to EFDA for the support in the organization of the workshop and to the Local Organizing Committee (E. de la Luna, Chair) in particular.
This special issue of Nuclear Fusion collects a number of full length papers that have been produced based on the material presented at the workshop. The papers have been refereed according to the usual high standard of Nuclear Fusion and present new and interesting aspects of transport barrier physics to the whole fusion community. The International Advisory Committee and the Guest Editor in particular are grateful for the support of Nuclear Fusion for the publication of the papers.