Joint effort designing the divertor dome

Between 17 and 20 March 2008, two divertor specialists from the Efremov Institute in St Petersburg, Russia, visited Cadarache to collaborate with the ITER Organization to advance the design of the divertor dome.

"Indeed, the work has progressed in a very effective way, and we advanced more in these few days of joint effort, than in the last several weeks," said Dr Alexey Makhankov, Responsible Officer for the procurement of the divertor dome in the Russian Domestic Agency. "Working together with the Divertor Section of the ITER Organization has been fundamental in reaching mutual understanding of the project requirements and of the manufacturing difficulties."

Dr Makhankov was accompanied by Dr Sergey Mazaev, design expert of the "Plasma-Facing Materials and Components" Laboratory in the Efremov Institute.

The dome is one of the three divertor plasma-facing components (the others being the Inner and Outer Vertical Targets), which is assembled onto the cassette body. It baffles neutral particles and protects the cassette body, while allowing helium and other impurities to be pumped away. It will be procured by the Russian Domestic Agency starting from next year.

Although the dome is not the divertor component subject to the highest heat flux, it is the most controversial from an engineering and physics stand point, as demonstrated by the two Design Change Requests, which are pending on it. Furthermore, a number of diagnostics are accommodated just beneath the dome, making its design even more challenging.

Dr. Mario Merola, Divertor Section Leader of the ITER Organization, declared that "We have been struggling for months to find the right compromise among the physics requirements, the minimization of the thermal and electromagnetic loads, the hydraulic constraints, the needs dictated by the diagnostic integrations and, at the same time, keeping in mind the importance of minimizing the manufacturing risks and costs. Working side-by-side here in Cadarache with our Russian colleagues allowed us to make important steps forward in the finalization of the design. It would have been impossible to obtain the same results in such a short time, should each group be sitting thousands of kilometres away from each other. I am now confident that we can finalize the dome design by end-April 2008, as specified in the divertor detailed plan to procurement. Further studies can then be carried out remotely by the Russian Domestic Agency."

A new bilateral meeting between the ITER Organization and the Russian Domestic Agency is planned on 15-16 April 2008 in St Petersburg to agree on the dome design supporting activities as well as to discuss the qualification of the manufacturing technologies and the procurement specifications of the divertor materials.