As many as 12 Russian scientists visited EFDA-JET during the last quarter of 2003.They installed hardware on the JET machine, worked on software development and participated in experiments. One of the areas they concentrated on was the detection of neutrons, which are born in fusion reactions, and then escape from the plasma, carrying valuable information about conditions inside the plasma. JET is already equipped with several neutron detection systems, and the goal of the collaboration with the Russian Federation in this area was twofold: to make faster measurements so that the effect of various fast events in the plasma on the fusion reaction rate could be studied, and to test a compact neutron detection system. Other aspects addressed in the collaboration included improvement of a system to measure tritium concentration with improved sensitivity, and to study plasma flows and energy transport. The success of this work has led to proposals for further collaboration which will be reviewed in May 2004.

In 2003 collaborations were established between EFDA-JET and two new international partners, the Russian Federation and the People’s Republic of China while collaboration with long-standing international partners US and Japan continued in full swing.

In the first collaboration with the People’s Republic of China, a Chinese scientist visited JET for 3 months during September 2003 – February 2004 bringing expertise on mechanisms for electron heat transport in JET plasmas dominated by electron heating. Further visits by Chinese scientists to EFDA-JET are under discussion.

Collaboration with the US and Japan in 2003 focussed on ‘joint experiments’ which have the potential to uncover new physics via co-ordinated studies spanning the combined operating space of participating tokamaks. 28 such experiments have been selected by leaders of large fusion facilities for execution in 2004. 50% of personnel assignments between the EU, US and Japan under a major collaboration agreement are now associated with such experiments. The scientific areas covered correspond to those identified as having high priority for research because the results could refine the ITER design. In the area of confinement physics, one such joint experiment shows that plasma performance (proportional to fusion gain) increases faster with increasing β (proportional to plasma pressure) than predicted by the scaling law used in the ITER design (see figure). The experiments were performed using the ITER plasma shape in the two participating tokamaks, DIII-D and JET, which differ in linear dimensions by almost a factor of 2. Both machines confirmed the more favourable dependence on β, leading to high confidence in the validity of the result.

The US is also collaborating in four important activities under a bilateral agreement betweenEURATOM and the USDoE. These include three of the 16 diagnostic enhancements which will be installed on JET this year and used in the Experimental Campaigns of 2005. These three diagnostics are: a system to detect and characterise the loss of fast particles from the plasma (including fusion-born α-particles) and particles accelerated to high energy by ion cyclotron resonance heating; an upgraded system for improved measurements of the ion temperature profile, plasma rotation and plasma purity, with higher sensitivity , and a highresolution system with broad coverage for improved electron temperature and density measurements to study barriers to energy transport in the core and the edge. The US contribution includes hardware design and procurement, and system commissioning. The fourth activity involves tests of a high-power prototype radio-frequency antenna, aiming at long-pulse operation at high voltage. This test is providing extremely valuable input to the development of an antenna based on the ITER design, which will be tested on JET.