During its new campaign the Joint European Torus (JET) says hello to more than 350 European fusion scientists. The world-wide largest magnetic fusion device currently prepares for a future deuterium-tritium campaign. Lorne Horton, JET Exploitation Manager, explains why coordinated European fusion research can be a role model for future ITER operations.

What are the major aims of the current experiments?

Firstly, we will test and expand the limits of JET performance to prepare the planned deuterium-tritium operation. In addition, we will study the scaling of disruption mitigation to more ITER-like conditions. This means we will raise the temperature and the density to create conditions that come closer to those in ITER’s vessel. Thirdly, we will extend the range of detached divertor experiments to maximum input power and quantify the trade-off between divertor heat load mitigation and core plasma performance.

What fuel will you use for the current experiments?

The experiments will initially be in deuterium. We expect to complement these experiments using hydrogen as the working gas, as the first step towards the planned JET isotope experiment, in which we compare hydrogen, deuterium and tritium. This also prepares for ITER’s non-active phase of operation.

Lorne Horton, JET Exploitation Manager. Picture: EUROfusion

Lorne Horton, JET Exploitation Manager. (Image: EUROfusion)

What will be most challenging now?

Most challenging will be combining high plasma performance, which will require maximum input power, with the power and energy limits of the ITER-like wall. Reaching this requires the high reliability of all of our important systems. This will be a major accomplishment and is viewed by the EUROfusion General Assembly, the highest decisive body in the EUROfusion consortium, as a necessary prerequisite to subsequently allow us to move on to experiments with tritium.

Have there been any changes made to the device since the last experimental campaign?

We are presently re-commissioning the ITER-like antenna, which is expected to help with tungsten control by changing the impurity transport in the plasma core. We have also relocated our High Frequency Pellet Injector to a position from which we expect more efficient Edge Localised Mode (ELM) pacing and thus also tungsten control. Moreover, JET has received a third Disruption Mitigation Valve, which will guarantee appropriate disruption mitigation at high current. Additionally, we will study the geometrical requirements for disruption mitigation by comparing and combining all three of our systems.

How many researchers are participating in total? Are they all physicists?

The researchers are primarily physicists. Without counting the hydrogen campaign, for which the Call for Participation has not yet been issued, we have almost 400 researchers participating from 24 different EUROfusion beneficiaries.

How did the establishment of EUROfusion support the current experimental campaigns at JET?

We’ve been working towards the EUROfusion system since the beginning of 2014. We benefited from the former EFDA funding to cover visits to JET for experiments in 2014, but the analysis at home was covered by a EUROfusion task. The combination of experiment preparation, execution, analysis and publication into one call this time around will, we hope, encourage a more holistic view to our work, with better preparation and more coordinated, in-depth analysis. This is the way ITER experiments will have to be run.
EUROfusion has also enabled us to better coordinate experiments between JET and the medium-sized tokamaks, ASDEX Upgrade and TCV. This means experimental proposals and schedules are discussed at a common planning meeting so that the best machine or machines are chosen in order to answer the related physics questions. In my eyes, it is a very good sign to have approximately the same number of researchers planning to come to JET now as in former campaigns, whilst EUROfusion and many of the same people are participating in experiments at ASDEX Upgrade, TCV and soon Wendelstein 7-X.

The JET experiments are primarily aimed at Mission 1, namely reaching ITER-like plasma regimes of operation, and Mission 2, namely investigating Heat Exhaust Systems, both are crucial for the ITER operation.