(Tokamak à Configuration Variable)
View into the experimental hall with TCV in the center as it looks
What is TCV ?
TCV is the main experimental facility on the Lausanne site of CRPP
TCV stands for "Tokamak à Configuration Variable" and tells thus the main
properties of this machine.
The tokamak concept is presently the most advanced concept for a thermonuclear fusion
reactor. A fusion power plant will convert the energy released on nuclear fusion reactions
of light atomic species (e.g. hydrogen) into electricity. It is a promising and almost
unlimited energy source for the coming centuries when other energy resources (oil, coal
and uranium) will be exhausted.
In a tokamak a hot plasma is confined in a toroidal configuration by magnetic fields -
partly produced by external coils and partly produced by an internal toroidal plasma
current. It allows for to produce high enough temperatures in the plasma so that
sufficient fusion reaction can take place under controllable conditions.
If you are interested in more details about Nuclear Fusion and Tokamaks- see our Fusion Server!
TCV however is too small in size in order to produce a significant number of fusion
reactions - it has never been designed to do so.
TCV possesses another interesting property which makes it unique in the zoo of existing
tokamaks in the world : The plasma cross section can be 3 times higher than wide - plasmas
can have elongations up to 3!
This feature opens the door to studies on plasmas of very different shapes! Other
tokamaks in the world are generally limited to a more or less fixed shape which is given
by the shape of vacuum vessel. Plasma physicists know that the performance of a fusion
reactor depends on the plasma shape. With TCV, fusion research has a versatile tool to
study the influence of shape on confinement and stability. TCV will thus gather important
informations for the design of a future Fusion Reactor.
Another important objective of TCV is to study this variety of plasma shapes with
microwave heating, more precisely with Electron Cyclotron Resonance Heating (ECRH). For
this purpose up to 9 strong microwave sources, called gyrotrons, are being installed
representing a power of 4.5MW additional heating for the plasma.
The aim of TCV is to extend the plasma parameter limits to easier regimes of operation.
Various scenarios of vertically-elongated plasmas will be systematically investigated.
Moreover, the possibility of maintaining vertical stability and optimizing the control
system constitute important stages of the project. The shape of the plasma cross-section
will be the major parameter to be modified during this research, thereby requiring a very
versatile machine. The mechanical strength of the coils and their mountings is sufficient
to withstand vertical forces of 200 tons. A plasma pulse in TCV needs 100MJ energy over 3
seconds. TCV's power is delivered by a flywheel generator which decouples the experiment
from the power supply grid network. TCV is a complex experiment where several hundreds of
parameters must be monitored and controlled, which explains the multitude of automated and
A series of plasma configurations (cross-sections) which have been produced in TCV are
shown in the following picture. Note that position and shape of the plasma can be
|Plasma major radius
|Toroidal magnetic field on the magnetic
|Additional heating (ECRH)
||max. 2 sec
|Vessel ohmic resistance
|Time constant of the vessel
The TCV tokamak (Tokamak à Configuration Variable) came into
operation in November 1992 and since has produced plasma currents above 1MA for pulse
lengths longer than a second.The maximum plasma elongation obtained so far was 2.58 and
1MW of microwave beam power was injected recently. The installation is now completed by
graphite tiles on the internal walls to reduce contamination of the plasma with heavy
impurities and by diagnostics installed around the tokamak to measure plasma parameters.
The complete auxiliary heating (4.5MW) by microwave injection should be completely
available by 1998.
What do we do on TCV ? (Experimental activities)
Production of plasmas with high elongations.
Shape dependence of energy confinement.
Study of different confinement regimes (H-modes, IOC , etc.) and
associated effects (ELMs, modes , etc.).
Electron Cyclotron Resonance Heating experiments (ECRH).
Electron Cyclotron Current Drive experiments (ECCD).
Development and test of models and algorithms for plasma position and
Plasma wall interaction , radiative plasmas boundary.
If you want to know more about TCV click here!