Fusion experiment conducted in the UK and prepared from Garching

Last JET discharge prior to temporary shutdown / Resumption of operation in a new form as of 2000

December 07, 1999
Experiments on the European fusion device, JET (Joint European Torus), at Culham, UK, were prepared, programmed, and monitored for the first time from an external fusion laboratory, Max Planck Institute of Plasma Physics at Garching, Germany. This 3 December 1999 was also the last day of experimentation on the device as a separate joint European project. The successfully conducted test will serve to help prepare resumption of operation of JET as of January 2000 in a new form of organisation.

The preparations for this "remotely controlled" day of experimentation took several days. What had otherwise been the task of JET physicists was now handled at IPP in Garching: Here members of the ASDEX Upgrade team, among them a former experimentation head at JET, Dr. Adrianus Sips, prepared part of the plasma discharges planned for the last day of operation. This included, in particular, planning and programming of the "time traces" for the electric currents that are to flow in the magnet coils. The evolution of these currents governs the shape of the magnetic cage and hence that of the plasma. In this way, the whole discharge scenario is modelled. The data sets which are calculated in the JET computer from Garching via a data transmission link then control the discharge on site at Culham. The actual course of events can be assessed by IPP physicists immediately afterwards in the form of test curves on the screens at Garching. These are then compared with expectations. Corrections for the next discharge are then decided with the colleagues at JET by phone and implemented on site.

The Garching physicists were most satisfied with this technical test. So Dr. Sips: "Communication went without hitch; at Culham and Garching everthing was well prepared." After this last day of operation, JET was subjected to a technical inventory before being handed at the turn of the year to the UKAEA fusion laboratory at Culham. As of January 2000 JET is no longer a separate joint project of the European fusion laboratories. Technical operation is now the responsibility of Culham laboratory, with scientists and technicians from the European laboratories being periodically delegated to JET for work in individual experimentation series. JET discharges will then frequently be prepared from the respective home laboratory on the basis of the recent successful test. This new form of organisation will allow the powerful JET experiment - the only fusion device at present capable of experimenting with deuterium-tritium plasmas - to be used beyond the previously envisaged shutdown for preparing the planned ITER experimental reactor.

JET - a story of success
From 1973 JET was jointly conceived and since 1983 has been jointly operated by the European fusion laboratories as the world's largest fusion experiment. Since then the device has brought the fusion programme very much closer to its goal - duplicating the energy generation of the sun on earth and deriving energy from fusion of atomic nuclei. The fuel used for this virtually inexhaustible source of energy is a low-density gas composed of the two hydrogen isotopes, deuterium and tritium. To ignite the fusion fire, the fuel has to be successfully confined in magnetic fields and heated to very high temperatures.

JET is meanwhile the world's leading fusion device, with the plasma produced already coming close to a power plant plasma in many respects. In 16 years of operation JET has achieved all scientific targets set. Outstanding among the wealth of results obtained, as the outwardly most visible achievement, were the record-breaking experiments of 1997. JET succeeded in releasing a fusion power of 16 megawatts, with 65 per cent of the applied heating power being recovered by fusion.

JET, of course, is not intended to produce a burning plasma in the new phase of operation either. This is the objective of the next step, the ITER International Thermonuclear Experimental Reactor now being planned as an international cooperation. With a fusion power of approx. 500 megawatts, it is to produce for the first time a plasma supplying energy for a long period and will test technical functions of a fusion power plant.

Isabella Milch

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