If someone was definitely not in hibernation, it was EUROfusion during the past half year. In February, the three tokamaks JET, ASDEX Upgrade and TCV were running simultaneously, accompanied by the first experimental campaign of the shiny new Wendelstein 7-X device. Two more experiments, MAST-U and WEST, are also about to flex their muscles.

TCV, the tokamak from the Swiss Research Unit, with the Neutral Beam on the left and the Phase Contrast Imaging diagnostic on the right. Picture: SPC

TCV, the tokamak from the Swiss Research Unit, with the Neutral Beam on the left and the Phase Contrast Imaging diagnostic on the right. Picture: SPC

An overachievement

EUROfusion’s man in the W7-X control room is Andreas Dinklage. He seems profoundly content as he reports on the finalised operation in Greifswald. About 40 percent of the hydrogen plasmas created in the stellarator could be used for pure scientific results. “An overachievement”, he calls it.

Overall, we shot about 940 discharge programmes.

Andreas Dinklage, Project Leader of the EUROfusion Work Package ‘Preparation and exploitation of the W7-X campaign’

The ‘One-team’ approach

The premiere Wendelstein 7-x campaign enabled unique workflows to set up open exchange and moreover, to apply to the daily status of the shiny new machine. Dinklage proudly calls it the ‘One-team approach’. During the three months of the campaign, the researchers met every morning in brief stand-up meetings. What was originally designed as an informative gathering to communicate updates on the technical status of the machine to a selected few, became an open discussion for everyone in the control room.

Carrying the risk on all shoulders

Dinklage’s ‘One-team approach’ is rather a one-programme approach. At other, well established, fusion devices around Europe and Switzerland, the experiments are separated into a home programme which is owned by the hosting Research Unit and the EUROfusion work package programme, even though the programmes as a whole are fully aligned along the Fusion Roadmap. The time for each programme on the machine depends on the arranged payment.

After the non-cooled divertor

In Greifswald, every participating team, whether it be the Max Planck internal researchers, EUROfusion’s scientists or the US delegation are able to carry the risks and benefits. “We didn’t care who paid how much but conducted a joint programme guided by scientific priorities, possibilities and quality.”  Dinklage and Task Force Leader Arturo Alonso are currently evaluating the feedback from all participants. Whether the next campaign, after installing the non-cooled divertor and new plasma facing components, is able to maintain this open spirit will depend on the results.

No competition within the family

Exciting times for stellarator research when, so far, the tokamak is the concept of choice for fusion research. “There is no competition. But Wendelstein must prove that we have stepped up to modern tokamaks. W7-X was built to mitigate most of the stellarator’s drawbacks. Fusion science is not a race between tokamaks and stellarators , as they are, most of all, a journey in which every unit complements the next on route to creating an economic reasonable fusion power plant”, states Dinklage. The heating at the new stellarator should, for example, deliver important results for ITER’s future plasma.

Drilling holes in the vessel

Meanwhile, the European tokamak team is pulling their own weight. One device in Switzerland has been working hard to keep up with its brother ASDEX Upgrade. “We have almost a new machine with the installed Neutral Beam Injector”, reports Stefano Coda. It took the company, which originally built the Swiss tokamak in 1992, almost three weeks to properly set up the machine for its new assets. Workers sat in the vessel and slowly drilled three holes in the wall to enlarge the gap for the new heating system.

Go the long way

TCV is fully integrated in EUROfusion’s MST1 family. We are already intensely interacting with the results from ASDEX Upgrade.

Stefano Coda, Deputy Task Force Leader of EUROfusion’s MST campaigns

According to the original schedule, experiments on the enhanced TCV would have overlapped with research at the established ASDEX Upgrade in Garching. EUROfusion decided then to shift the start of the campaign in Switzerland from January to April 2016. On the one hand, it reduced the extra pressure on the teams working in both Germany and Switzerland. On the other, EUROfusion then needed to reorganise the itineraries of more than 200 scientists.

60 valuable shots

This spring, Coda is quite busy and hard to catch on the phone. He will spend hours in the control room during the peak period from April until July. “We are able to operate with a total rate of 130 shots per week and we can now guarantee the 60 per week as is necessary to deliver scientific results”, he says.

An open Swiss control room

“The outcome will materialise in mutual scientific papers from researchers dealing with both tokamaks. “I am happy that we opened up our control room for this fruitful exchange with international scientists. The atmosphere is very collegial, much more than it has been before”, says Coda.

The Swiss tokamak was so happy about its new feature that it shared a message on Twitter on April 18:

I have a new gyrotron, a microwave source, which is quite powerful (750‘000 Watts), to warm me up! I‘m eager to try it!

For more updates from TCV itself follow the machine on Twitter: @TCV_tokamak.

Prepare the heir

The step ladder approach to fusion experiments is shown by the choice of fuel: first, hydrogen or helium, then deuterium and at the end, the most powerful fusion fuel, deuterium and tritium. When ITER will operate in its so-called ‘active phase’ it will use the nuclear fuel tritium, the top of the ladder. EUROfusion now investigates ITER’s ‘non-active phase’. Hence, ASDEX Upgrade and TCV have run helium experiments during the first half of the year. JET will complement the preparations of ITER’s non-active phase with a hydrogen campaign this summer.

A wide range of assets

EUROfusion connects all machines in support of ITER and ultimately of the fusion power plan.

Xavier Litaudon, Head of EUROfusion’s ITER Physics department

Every machine in the EUROfusion programme has its unique features which serve the latest fusion research: TCV possesses a flexible magnetic field and the new heating system. ASDEX owns a tungsten first wall. JET maintains unique capabilities which enables it to operate with a deuterium-tritium mixture surrounded by an ITER like wall. And that is not all, the EUROfusion family will welcome two more mates into the tokamak team: the upgrade of MAST in Culham will be EUROfusion’s first spherical tokamak. The other device WEST, hosted in French Cadarache, is the only European tokamak which comes with an actively cooled divertor. It will start operating as a test in autumn this year. When others go into hibernation, EUROfusion powers up.

“Our task is to ensure that we get the most out of the results”, says EUROfusion’s Experimental Programmes Group Leader Marie-Line Mayoral. Therefore, EUROfusion’s scientific programme in the ITER Physics Department has been organised into 14 work packages. Most of the deliverables from the work packages rely on the results of current or future campaigns in the Joint European Torus (JET), the Axially Symmetric Divertor Experiment (ASDEX) Upgrade, the Tokamak à Configuration Variable (TCV) as well as in the upcoming Tungsten (W) Environment in Steady-state Tokamak (WEST) and the upgrade of the Mega Ampere Spherical Tokamak (MAST). This is demanding for the consortium, which not only promotes high priority experiments but also coordinates scientists from 29 European Research Units and further, ensures the scientific exchange within the community. Of course, the consortium also contributes financially.