Advances in Burning Plasma-Related Physics and Technology in Magnetic Fusion

The worldwide magnetic fusion program is currently focused on preparing for burning plasma experiments on ITER, an exciting frontier.   The higher plasma temperature and pressure required, and particularly the larger volume, pose new challenges compared to present experiments.  Much larger stored energy and power per surface area imply greater attention to handling the heat leaving the device, and reducing transient events.   Coordinated research has made great progress in understanding fundamental plasma physics and resolving practical issues.  Turbulence in the plasma core and edge is measured to an unprecedented detail, and simulations are increasingly accurate, particularly in the high T regime.   Significant advances have been made in understanding the formation, and predicting the height, of edge transport barriers which set the boundary conditions for the fusing core.    Several techniques have been demonstrated to mitigate the Edge Localized Modes which typically occur in these barriers, and would result in excessive transient heating on ITER.   New high performance regimes are being pioneered on US facilities which are naturally free of such transients.    Advances in plasma-wall interactions are giving new information on the expected edge heat flux profile.  Several experiments are assessing operation with metal plasma facing components, which will be needed on ITER to reduce retention of tritium.

The MFE program is also addressing issues which will be needed to develop practical fusion energy beyond ITER.  Higher wall temperatures needed for efficient power generation, and even higher power densities and pulse lengths, increase the challenge of power handling but may ease some issues such as tritium retention.    Steady state operation also requires non-inductive sustainment.  RF current drive is being assessed at relevant parameters in US devices, and new superconducting Asian tokamaks aim to demonstrate long pulse regimes before they are assessed on ITER.   New challenges of fusion nuclear and materials science must be resolved to handle the much larger nuclear fluence in a demonstration fusion device.    It will be critical to sustain and even increase the pace of research in all of these areas, to prepare for exploitation of ITER and achieve a timely resolution of the remaining issues for fusion energy.   Advances in technology are also impressive, and important.  For example, new high temperature superconductors may enable higher field, more compact fusion reactors.