The following article is republished with permission from the December issue of EFDA'sFusion in Europe magazine.
After having served European fusion research for four years, the High Performance Computer for Fusion (HPC-FF) completed operation in June 2013. HPC-FF provided scientists with significant computing power (100 teraFLOPS), enabling advances in plasma and materials modeling and fusion technology simulations. The European Atomic Energy Community (EURATOM) funded HPC-FF together with the European Fusion Development Agreement (EFDA) and the Forschungszentrum Jülich, Germany, whose supercomputing center operated the facility. Now fusion modeling work has moved to the significantly more powerful Helios computer, which has a peak performance of around 1500 teraFLOPS. Helios is a Japanese-European facility under the 'Broader Approach' agreement and is located in Rokkasho, Japan.
Turbulence simulations: a key application
Altogether, more than 200 projects were run on the HPC-FF. Some of the major activities were simulations of plasma turbulence for a range of fusion devices. Turbulence is the key process governing energy confinement in tokamak plasmas. Simulating turbulence in fluids is already a demanding task, but simulation in plasmas brings the additional complexity of charged particles in an electromagnetic field. The processes also take place on a broad range of time and length scales, and detailed simulations therefore require the use of high-performance computers. Another important field of investigation, for which HPC-FF was used, was the study of plasma instabilities. These phenomena can cause rapid energy losses in the plasma, which in large machines like the International Thermonuclear Experimental Reactor (ITER) could result in damage to the reactor wall. A third focus of activity was the simulation of the behaviour of potential reactor wall materials under high-energy neutron flux. These conditions are characteristic of the deuterium-tritium plasmas that will be used in the second phase of the ITER experiment and in future fusion demonstration and power plants.
"The HPC-FF platform and team - along with the high-level support team - have been invaluable to the European fusion theory community. They have facilitated many important scientific discoveries, including an explanation of the observed reduction of ion profile stiffness at the Joint European Torus (JET) tokamak. This effect has striking consequences, in particular, for burning plasma experiments and is likely to enhance ITER's predicted fusion performance." Frank Jenko, IPP
High-level support team continues to provide assistance
HPC-FF is the first shared high-performance computer facility for the European fusion community. To ensure maximum benefit from the facility, a high-level support team was put in place. Its role is to help scientists optimize their codes for the massively parallel computer architecture of HPC-FF. The team consists of a core group based at the Max Planck Institute for Plasma Physics in Garching (IPP), Germany, and other support staff provided by the associates. All members are HPC experts with a background in developing large scientific applications, including particular expertise in numerical algorithms and in graphical support and visualization. The high-level support team will continue to provide invaluable assistance to the European fusion scientists using the Helios system and thus ensure a smooth transition to the new facility.
The 'Broader Approach' agreement for complementary research and development was signed in February 2007 between EURATOM and the Japanese government. It provides a framework enabling Japan to conduct research and development over a period of ten years to support ITER. More on the 'Broader Approach' agreement, here.
- Tim Hender and Darren McDonald