Special issue containing papers presented at the 12th International Workshop on H-mode Physics and Transport Barriers

The 12th International Workshop on H-mode Physics and Transport Barriers was held at the Princeton Plasma Physics Laboratory, Princeton, New Jersey, USA between September 30 and October 2, 2009. This meeting was the continuation of a series of previous meetings which was initiated in 1987 and has been held bi-annually since then. Following the recent tradition at the last few meetings, the program was sub- divided into six sessions. At each session, an overview talk was presented, followed by two or three shorter oral presentations which supplemented the coverage of important issues. These talks were followed by discussion periods and poster sessions of contributed papers. The sessions were: Physics of Transition to/from Enhanced Confinement Regimes, Pedestal and Edge Localized Mode Dynamics, Plasma Rotation and Momentum Transport, Role of 3D Physics in Transport Barriers, Transport Barriers: Theory and Simulations and High Priority ITER Issues on Transport Barriers.The diversity of the 90 registered participants was remarkable, with 22 different nationalities. US participants were in the majority (36), followed by Japan (14), South Korea (7), and China (6). This special issue of Nuclear Fusion consists of a cluster of 18 accepted papers from submitted manuscripts based on overview talks and poster presentations. The paper selection procedure followed the guidelines of Nuclear Fusion which are essentially the same as for regular articles with an additional requirement on timeliness of submission, review and revision. One overview paper and five contributed papers report on the H-mode pedestal related results which reflect the importance of this issue concerning the successful operation of ITER. Four papers address the rotation and momentum transport which play a crucial role in transport barrier physics. The transport barrier transition condition is the main focus of other four papers. Finally, fouradditional papers are devoted to the behaviour and control of Edge Localized Modes.The selection of topics and overview speakers and the scientific programme were carried out by the International Advisory Committee, consisting of: R. Groebner (GA, USA), T.S. Hahm (PPPL, USA--Chair), A. Hubbard (MIT, USA), K. Ida (NIFS, Japan), S. Lebedev (Ioffe Institute, Russia), N. Oyama (JAEA, Japan), G. Saibene (F4E, EU) and W. Suttrop (IPP, Germany).Their work, advice, and participation contributed to the success of the meeting. Finally, I would like to express deep gratitude to J. Jones and B. Sarfatywho took care of numerous issues relating to the organization of the meeting, and to J.K. Park and several graduate students of the Princeton University Plasma Physics Program for helping with the transportation of participants.