So you wanna build an RF driven tokamak?*

Imagine you must develop the current drive actuator for a major tokamak experiment.  No pressure, but this is one of the most critical issues for the viability of a tokamak fusion reactor.  A number of studies have identified efficient, robust current drive systems that can survive the harsh reactor environment as critical for fusion success (FNSF [Chan FST 57 2010, Chan NF 51 2011, Garafalo NF 54 2014] and ARIES-AT [Najmabadi FED 80 2006]). Based on system efficiency and wave penetration, lower hybrid current drive (LHCD) and ion cyclotron range of frequency (ICRF) current drive are the among the most effective actuators to provide the current and pressure profiles needed for efficient fusion electricity production.  To deploy LHCD and ICRF requires integrated physics and state-of-the-art technical solutions for coupling high power compatible with reduced plasma material interactions and a high performance edge and core plasma.  Where to start?  Although an iterative process, the first step is to identify the RF scenario that maximizes the current drive efficiency.  The primary output from this step is to identify the proper wave spectrum.  The proper spectrum is one that optimizes wave penetration, single pass absorption and current drive efficiency.  Next, the antenna/coupler is optimized to excite the wave spectrum in the plasma and coupling is a key attribute to assess.  In both LHCD and ICRF, the edge density profile has a dramatic impact on wave coupling to the plasma and can require a particular antenna spectrum for optimization; there could be a trade-off between wave and antenna spectra.  Another consideration is antenna compatibility with the plasma edge and plasma material interactions.  In this tutorial, the basic RF physics principles for LHCD and ICRF needed for developing integrated physics solutions will be presented.