Low power density ion cyclotron arrays for fusion reactors

• A low power density, high directivity, FW heating and current drive launching structure is proposed for use in a commercial fusion reactor.
• The structure, integrated in the reactor blanket first wall, is modular, unobtrusive and imposes no specific constraints to the blanket functions.
• It may significantly reduce the undesirable effects of FW evanescence in the plasma scrape off layer such as increased thermal wall loading, localized hot spots, impurity production, and enhanced E × B0 particles convection.

Ion Cyclotron Radio Frequency (ICRF) Heating and Current Drive (H&CD) is a well established technique of auxiliary heating in present tokamaks, as it features high on-axis heating and current drive efficiencies associated with proven and low cost technology. An important limiting factor to the use of ICRF as candidate heating method in a commercial reactor is linked to the evanescence of the fast wave in vacuum and in most of the SOL layer, imposing proximity of the launching structure to the plasma boundary and causing high RF standing and DC rectified voltages at the plasma periphery, possible voltage breakdowns and enhanced local wall loading. Further to previous work (Bosia et al., Ion Cyclotron and Lower Hybrid Arrays applicable to Current Drive in Fusion Reactors, in: AIP Proc. of 20th Topical Conf on RF Power in plasmas No. 1580, 2013, 215) developing new concepts for Ion Cyclotron and Lower Hybrid Heating & Current Drive arrays, based on the use of periodic structures, a practical example for an in-blanket IC array for DEMO1 is presented in this study.