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Press Releases

Brussels, 23 September 1997

JET Starts Experiments with Increased Fusion Power

JET commence des expériences avec une puissance de fusion accrue

JET is the flagship of the Community Fusion Programme based at Abingdon (UK). It is now the only experiment worldwide able to operate with the fuel mixture of possible future fusion power stations.

Over the last few days, JET has started a series of experiments with equal parts of the two heavy isotopes of hydrogen, deuterium and tritium. One of these experiments has already produced more than 12 megawatts of fusion power (11 MJ of fusion energy). This is 6 times the fusion power produced in the world’s first controlled demonstration of fusion energy carried out on JET in 1991 with a more dilute fuel mixture.

An important measure of success is the ratio of fusion power produced to power input to the plasma and in this respect a new record has been obtained. This was 50%, and about twice that previously achieved. These three results for fusion power, fusion energy and the ratio of fusion power to input power all set world records.

These new results mark the start of a broad-based campaign of several weeks which will address issues of both fusion power production and the physics of high-performance plasma confinement in the geometry and operating conditions planned for the International Thermonuclear Experimental Reactor, ITER, currently in an advanced design state.

These achievements confirm the lead position of Europe in magnetic fusion R&D, made possible by JET’s place in the Community Fusion Programme and its strong partnership with the European Associated Laboratories.

Fusion offers the potential for a new source of safe and environmentally-friendly energy (no greenhouse effect) based on a virtually inexhaustible fuel supply and would be particularly suited for baseload electricity generation.

For further information, please contact:

Fusion Programme
Fax: +32 2 296.42.52
Stephen GOSDEN
Press & Information Officer
E-mail :

The JET Project - In Brief

JET (the Joint European Torus, based at Abingdon, Oxfordshire, UK) is the flagship of the Community Fusion Programme which aims at developing magnetic confinement fusion as a new, clean source of safe and environmentally-friendly energy to provide abundant power for the future of mankind.

There is a workforce of about 700 from all the EU countries plus Switzerland. The annual budget is ECU 78 million (approx. £54 million).

Construction of JET started in 1978 and it has been operational since 1983. Since the closure of the US tokamak TFTR in Spring 1997, JET is the only experiment worldwide able to operate with the deuterium-tritium fuel mixture of a future commercial fusion power station. Furthermore, JET is the nearest in scale and geometry to the International Thermonuclear Experimental Reactor (ITER) which is currently in its Engineering Design Activities. At present, JET's programme is approved to the end of 1999.


Energy is produced when light atoms such as heavy isotopes of hydrogen are fused together to form heavier atoms such as helium. This is the process taking place in the Sun and stars. To do it on Earth is difficult, requiring even higher temperatures than in the Sun. In JET the hot ionised gas is confined by a magnetic field in a toroidal configuration (doughnut shape) known as a Tokamak.

Nuclear fusion will be important for long-term energy supply. The fuel (deuterium from water and the common mineral lithium from which the radioactive gas tritium is made) for this clean source of safe and environmentally-friendly energy is virtually inexhaustible:

Deuterium/Tritium Experiments

In November 1991, a world first, JET produced controlled fusion power, nearly 2MW for over one second with a dilute fuel mixture of just 10% tritium.

Since then, JET has been rebuilt with a "divertor" to handle higher levels of exhaust power, and deuterium experiments in the ITER geometry have made essential contributions to the ITER divertor design and provided key data on heating, confinement and fuel purity. This has allowed the size, heating requirements and operating conditions of ITER to be defined.

When JET resumed D-T operation in June 1997, the most important result was that the threshold power for high confinement was more than 20% lower in D-T, a very positive result for ITER.

Over the last few days JET has started a broad-based series of experiments which will use various D-T mixtures to address issues of both fusion power production and the physics of deuterium-tritium plasmas in ITER conditions (see current press release for latest results).

The present campaign of D-T experiments will last several weeks and will allow a more accurate assessment of the ignition margin and heating requirements for ITER. The experimental programme then continues with a period of ITER physics studies in deuterium, before the third stage of the JET divertor programme begins in early 1998 with the remote handling installation of an ITER-specific divertor target assembly. This will demonstrate for the first time one of the technologies which is vital for both ITER and a fusion power station.