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TCV

(Tokamak Configuration Variable)


View into the experimental hall with TCV in the center as it looks today.

 


What is TCV ?

TCV is the main experimental facility on the Lausanne site of CRPP

TCV stands for "Tokamak 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 computer-controlled tasks.

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 controlled independently.


TCV Parameters

Plasma height max. 1.44m
Plasma width max. 0.48m
Plasma major radius 0.875m
Plasma current 1.2MA
Plasma elongation max. 3
Aspect ratio 3.6
Toroidal magnetic field on the magnetic axis max.1.43T
Additional heating (ECRH) max.4.5MW
Transformer flux 3.4Vsec
Loop voltage max.10V
Plasma duration max. 2 sec
Vessel width 0.56m
Vessel height 1.54m
Vessel ohmic resistance 55mW
Time constant of the vessel 6.7ms
Heating temperature max.350C

 

The TCV tokamak (Tokamak 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 shape control.

  • Plasma wall interaction , radiative plasmas boundary.

 

If you want to know more about TCV click here!

 

CRPP EPFL
CH-1015 Lausanne
Switzerland
Phone: ++41 21 693 3482
FAX : ++41 21 693 5176 
E-mail : Edith.Grueter@epfl.ch

Last modified: 02-Mar-2004   

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