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CEA participation in JET Bas de page

Cutaway diagram of the JET torus (photograph courtesy of EFDA-JET). The JET machine is a large tokamak device of approximately 12 metres high. At the heart of the machine there is a toroidal (ring-shaped) vacuum vessel of major radius 2.96 metres with a D-shaped cross-section. The plasma volume is typically ranging between 80 m3 - 100 m3.


Inside of the JET torus, July 2005, following a 16 month shutdown period for extensive enhancements, including an ITER-like divertor at the bottom (photograph courtesy of EFDA-JET)

JET (Joint European Torus JET Website) is the world's largest nuclear fusion research facility. The experiment is based on the UKAEA (United Kingdom Atomic Energy Authority JET Website) site at the Culham Science Center close to Oxford (United Kingdom). The work is being carried out by a team of scientists from all the EU countries plus associated countries. Other international scientists also participate in the programme. JET is presently the only experiment able to operate using the deuterium-tritium fuel mixture planned for future thermonuclear power stations.

The JET Joint Undertaking was established in June 1978 to construct and operate the device and it was coordinated by EURATOM (the European Atomic Energy Community). The JET machine was built between 1978 and 1982 within the framework of a community enterprise financed up to 80% by the fusion programme, up to 10% by the host country (the United Kingdom) and up to 10% by all European partners

The device is in operation since 1983. In November 1991, JET became the first experiment to produce controlled fusion power. In 1997 JET operations included successful experiments using the mixed deuterium-tritium fuel, and reached a record 16MW of fusion power. In December 1999 the JET Joint Undertaking came to an end. Throughout this period, French engineers and researchers have made a significant contribution to all aspects of the project. 

The partners opted for a continuation of this experiment beyond this date, but within the framework of a new "EFDA" structure (European Fusion Developement  Agreement EFDA EFDA website). The UKAEA has taken over the safety and operation of the JET facilities on behalf of its European partners. The experimental programme is being co-ordinated by the EFDA Close Support Unit (CSU), led by an EFDA JET Associate Leader based at Culham. This agreement reinforces the role played by the partners in the choices and implementation of the scientific programme. Thanks to this new organisation, European physicists thus have the possibility of using JET more often, to monitor experiments as they are carried out, while using remote techniques to carry out scientific analysis or hold videoconferencing meetings.

The JET fusion science has focused into a physics and technology basis for preparing for ITER ITER website, the International Thermonuclear Experimental Reactor. In this context, the CEA-EURATOM association is closely involved in the JET programme. Since 2000, our participation is at the level of 180-200 professional months per year that covers a wide range of scientific activity:       

  • coordination of the scientific programme and enhancement within the EFDA-CSU;

  • coordination of scientific experiments, definition and implementation at JET together with their scientific analysis;

  • participation in the operation of the JET facility with the UKAEA-EURATOM association;

  • designing new components at JET (e.g. new diagnostics, new heating and fuelling systems, new plasma facing components);

  • studies technological issues on critical points such as detritiation methods or erosion of plasma facing components


The large number of publications and presentation at various conferences (up to 130 during the years 2000 to 2005) lead by experts from the CEA-EURATOM association gives also a good indication of our high level of commitment in the scientific exploitation of the JET facility. The most recent CEA-EURATOM association involvement could be illustrated by two majors achievement: 

  • CEA experts have played a leading role by developing new real-time measurements and feedback control algorithms that have been implemented to successfully maintain the fusion power and/or the safety factor (1) profile (q-profile) that controls the plasma confinement and stability properties in steady state conditions.

  • CEA experts have recently and successfully installed a new equipment (called diagnostic) on JET to characterise the plasma properties and in vessel components in the infra red domain. Indeed, the objective of this enhancement project lead by the CEA-EURATOM association is to provide a wide angle view and an infra red camera for thermography in the main chamber and divertor, aiming at real-time machine protection and for analysis of the power deposition in both divertor and main chamber during plasma instabilities and loss of fast (including fusion born alpha) particles.

(1) :  Safety factor “q”: number of turns the helical magnetic field lines in a tokamak make around the major circumference per single turn round the minor circumference. This has no connection with the ordinary sense of “safety” but relates to plasma stability

Among the first Infra-red view of the inside JET taken in 2005 with the new equipment designed by the CEA team. (photograph courtesy of EFDA-JET)

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