Chapter 11: The Heating and Current Drive Systems of the FTU

High-frequency wave systems with high-power density launching capability have been the preferred choice to heat the Frascati Tokamak Upgrade (FTU) because of physics arguments (electron heating at very high density) and space constraints from the compactness of the machine design (8-cm-wide port). They do include an 8-GHz lower hybrid current drive (LHCD) system, a 140-GHz electron cyclotron resonance heating (ECRH) system, and a 433-MHz ion Bernstein waves system (IBW). The technical aspects of these systems will be reviewed in this article. The main features of the design include the following: (a) a very compact conventional LHCD grill with a compact window to keep the vacuum on 48 (12 columns, 4 rows) individual waveguides allowing the maximum flexibility in spectra generation to be achieved; power handling up to [approximately equal to]10 kW/cm² has been achieved, (b) ECRH launchers designed as a quasi-optical system (implementing ITER relevant solutions) retaining the maximum flexibility in the equatorial launcher (poloidal/toroidal steerability) to exploit a variety of scenarios, (c) a two-waveguides launching array making the IBW experiment on FTU unique. Other technical aspects (sources, transmission lines, etc.) are also reviewed. The development of a new ITER relevant lower hybrid launcher, the passive active multijunction, is described.