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6) Long pulses: a speciality of Tore Supra (p 1 - 2 )
What recipe is needed to achieve a long pulse? A number of parameters come into play. First of all, the magnetic configuration : a system is needed to allow for continuous confinement of particles (supra-conducting magnet for the toroidal magnetic field, non inductive current generation using hybrid frequency heating for the poloidal magnetic field). Then, power and matter injection: heating systems and particles plasma supply working over long periods are needed. And then, of course, as a corollary, the power and matter extraction : plasma facing components cooled by flow water are needed, capable of withstanding enormous heat continuously without excessive temperature rise, while evacuating particles. Then, the plasma parameters must be well chosen (magnetic field, plasma current, density and so on), so that the magnetic equilibrium is stable, the coupling of heating to plasma is satisfactory, the efficiency of current generation optimal and the plasma facing components do not overheat. All this must be monitored in real time thanks to efficient diagnostics in order to be able to intervene on control systems if necessary (magnets, heating, gas injection and so on).
To go further and thus enrich the database, which is used to scale the next step ITER, Tore Supra is now aiming at a performance of 25 MW injected for 1000 seconds (or 25 GJ). At this stage, it will only be one order of magnitude down from ITER in terms of energy (intended for 200 GJ) and will achieve the same pulse duration (1000 s). Moreover, even if the coupled power in Tore Supra is lower, the power density (i.e. the power divided by the surface collecting it) attained on plasma facing components is comparable, the machine being smaller. This is therefore the opportunity for real life testing of next step technologies. To be up to these ambitious goals, Tore Supra has undergone a facelift:
In 2001, Tore Supra starts again in a totally new configuration, with a CIEL start-up limiter (LDC) enabling tests of the plasma facing component technology. In 2002, the whole CIEL project will be up and running, with the pumped toroidal limiter (LPT): the machine will then be ready to extract 25 MW continuously, all ready to break the GJ record. In parallel, progress in heating systems is still being made, with the first stage CIMES1, which, with the enhancement of the hybrid system, will help along the path to even longer pulses.
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