TCV Auxiliary Heating

Electron Cyclotron Resonance Heating & Current Drive System

Bearing in mind that present tokamak research is above all research on how to understand and manage plasma at extremely high temperatures, one can readily see importance of any method which allows plasma heating.

Coupling resonant electromagnetic microwaves to plasma is one of the most common methods of plasma heating (yes there is certain analogy to a microwave oven…). If the resonance condition is fulfilled, that means if the frequency of the microwaves excites one of the plasma proper frequencies, the waves can transfer their energy to plasma – which means they can heat the plasma.

A special case with the heating microwave frequency equal to the gyrofrequency of the plasma electrons (i.e. equal to the electron rotation frequency in the magnetic field which confines the plasma), or to its harmonics,  is called Electron Cyclotron Resonance Heating (ECRH).

ECRH can substantially support the primary plasma heating, which in the case of the tokamaks is Ohmic heating (the electrical current Ip causes plasma heating by Joule effect – the same effect drives household electric heaters). The ECRH additional heating is of great importance as the efficiency of the primary Ohmic heating decreases with the plasma temperature.

Since the magnetic field is a function of the tokamak major radius, only electrons located at a given major radius will resonate and absorb the energy. Thanks to this fact the heat diffusion into other regions of plasma can be studied.

Moreover, when the resonant electromagnetic wave has a component parallel to the field, it can support the electric current in the plasma. The method is referred to as Electron Cyclotron Current Drive (ECCD).

TCV with its ECRH-ECCD System composed by 9 gyrotrons (4.3MW) has been the first machine in world which has reported plasma with full current in ECCD, that is we managed to run shots with no current induced from the tokamak transformer.

With such a modern, powerful and flexible ECRH-ECCD system, the CRPP has been prolific in the publishing of related articles. We have also been active in the design and theoretical study of gyrotrons. Information on these subjects is given in our dedicated ‘ Research and achievements ‘ page.

For more details on the ECRH-ECCD physics please consult the ‘ Basic physics of ECRH-ECCD ‘ page.

Foreseen upgrades of the TCV Auxiliary Heating consist on the installation of a Heating Neutral Beam System, on a possible X3 power increase of the TCV ECRH-ECCD System as well as on the installation of fast polarizers in one transmission line.