An important requirement for TCV is to become capable of heating plasmas at relatively high density and β and to be able to vary the Ti/Te ratio over a wide domain including the case of equal temperatures.
The only way this can be achieved in a relatively small device is to supplement the existing electron heating with direct ion heating in the form of neutral beam injection (NBI).
In addition, the availability of neutral beam heating enables the pursuit of physics investigations in several areas of MHD (fast particle modes, Neoclassical Tearing Modes, Resistive Wall Modes), heat transport and momentum transport.
Ongoing work: Feasibility and preliminary design of heating beams for the TCV Tokamak
The injection of 1 MW Deuterium or Hydrogen beams (one injector) with energy below 35 keV would allow to access Ti/Te ratio >1 and higher plasma pressure in both L- and H-mode in high density plasmas compatible with third harmonic (X3) EC heating (simulation by ASTRA code )
The tangential double path NB alignment is considered to decrease the shine-through losses and avoid strong first orbit losses, especially at low plasma current.
A.N.Karpushov, B.P. Duval, R.Chavan, E.Fable, J-M.Mayor, O.Sauter, H.Weisen; A scoping study of the application of neutral beam heating on the TCV tokamak ; Fusion Engineering and Design, 86 (2011) 868–871 DOI:10.1016/j.fusengdes.2011.02.077