JET starts experiments with increased fusion power
The Joint European Torus (JET), a major component of the Community's specific programme of research and training in the field of controlled thermonuclear fusion, has started a broad-based series of experiments aimed at addressing 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. Based at Abingdon, Oxfordshire (UK), JET was started in 1978 and has been operational since 1983. JET is the largest magnetic fusion project in the world. Its principal aim is "to obtain and study a plasma in conditions and dimensions approaching those needed in a thermonuclear reactor". Since the closure of the US tokamak TFTR in Spring 1997, JET is the only experiment worldwide able to operate with the deuterium-tritium (D-T) fuel mixture of possible future fusion power stations. Furthermore, JET is the nearest in scale and geometry to ITER, the design of which is being conducted jointly by Euratom, the USA, Japan and Russia. In November 1991, a world first, JET produced controlled fusion power, nearly 2MW for over one second with a dilute fuel mixture. 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. 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 in 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% - 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. 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. 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.