Category Archives: Germany

Jülich Forschungszentrum

Jülich

Bringing the Solar Fire to Earth: Fusion Research

On the way towards an international fusion reactor

In the south of France, the international fusion reactor known as ITER is currently being constructed. For fusion researchers worldwide, this is the most important large-scale experiment, as ITER will be the first reactor to generate 500 million watts of fusion power in pulsed operation for around eight minutes. ITER will help to answer open questions before the first demonstration power plant for fusion power (DEMO) goes into operation. Whether this will be successful and whether we will come closer to the dream of an almost inexhaustible and clean source of energy essentially depends on the resistance of the reactor’s inner walls against heat and plasma particles. Jülich scientists have special expertise in the development of suitable wall concepts with resistant wall materials.

Fusion has enormous potential. The energy required by a family of four in Germany over a period of one year could be covered by around 2 litres of water and 250 grams of stone. This is based on the assumption that we will succeed in imitating the processes that occur inside the sun in power plants. In other words, we must first be able to use the fusion of light atomic nuclei to generate energy. This is the aim of fusion research. The advantages are that the light atomic nuclei lithium and deuterium can be readily extracted from natural resources, fusion processes are inherently safe and the formation of long-lived radioactive waste can be minimized by selecting suitable materials for the construction of the reactor.

Controlling plasma with a temperature of 100 million degrees

The challenge involves reconstructing conditions as they exist inside the sun in a fusion device – or to put it another way, keeping plasma with a temperature of 100 million degrees stable despite all of the processes that occur between the plasma and the surrounding vacuum vessel walls. Jülich scientists are experts in investigating this process, which is known as plasma-wall interaction and represents one of the keys for constructing future fusion devices. The construction of what is currently the most important reactor for fusion research, ITER, is no different. It is being built in the south of France within the framework of an international cooperation. ITER (Latin for “way”) is considered a milestone on the road towards delivering electricity generated by fusion directly to the end user. ITER will be the first fusion experiment to produce 500 million watts of fusion power in pulsed operation for around eight minutes.

Measuring techniques and modelling for ITER

JET fusion deviceFrom 2011, the divertor area of the JET fusion device at the lower end of the photomontage will consist entirely of tungsten elements developed at Jülich.
Copyright: EFDA-JET

For this project, Jülich researchers are developing and testing measuring techniques which can be used to accurately record information on factors such as temperatures, densities and magnetic fields as well as on impurities in the plasma. Using the supercomputers at Jülich, they calculate important parameters for the design and construction of future devices. A critical point here is lining the vacuum vessel. For this purpose, Jülich scientists are investigating whether a vacuum vessel wall made of graphite and tungsten would be able to withstand the extremely high loads over the course of years of operation. In the ITER divertor – the most highly loaded area of the walls – scientists expect heat fluxes that are ten times greater that those in aircraft turbines or on the fuel rods of a nuclear power plant.

Instabilities in the plasma can cause even stronger heat pulses for fractions of a second. In addition, the materials must also be resistant to the neutron radiation that occurs due to the nature of the fusion process. In the ITER divertor, solid tungsten is to be used. Jülich scientists and engineers were involved in developing this material, which is currently being tested at JET. JET (Joint European Torus) is located near Oxford in the United Kingdom and is currently the largest and most successful fusion experiment in the world. Forschungszentrum Jülich plays a key role in operating this important ITER forerunner.

Wendelstein 7-X stellarator possible alternative to tokamak

Jülich’s expertise is also much sought after for a fusion device in Germany: the Wendelstein 7-X stellarator in Greifswald, which aims to bring us much closer to implementing a fusion reactor in continuous operation. Forschungszentrum Jülich supports the Max Planck Institute of Plasma Physics in constructing this experiment and is responsible for designing and fabricating important electrotechnical and mechanical components. Jülich thus contributes its extensive technological experience in constructing fusion devices. With its expertise in plasma-wall interaction, Jülich will also play an important role in the scientific use of Wendelstein 7-X. Commissioning will begin in 2014. Due to its advantages in continuous operation, the stellarator is considered an attractive alternative to the tokamak concept, which is currently the most advanced type of fusion reactor.

Large-scale equipment for fusion research

For their extensive experiments, Jülich scientists together with their partners in Germany and abroad make use of both national and international large-scale facilities in fusion research as well as smaller and more specialized equipment. In Jülich, these facilities are the PSI-2 linear plasma generator, the JUDITH and MARION thermal load experiments as well as numerous laboratory devices; in Germany, the ASDEX Upgrade tokamak and, from 2015, the Wendelstein 7-X stellarator in Greifswald; in the European context, they include the large-scale European experiment JET in the United Kingdom, as well as the Magnum-PSI linear high-flux device in the Netherlands. Experiments on limiting instabilities in the plasma boundary layer are also being conducted by Jülich scientists at the DIII-D tokamak in San Diego, USA.

German Federal Ministry of Education & Research

German Federal Ministry of Education & Research

Fusion Research – how the sun and stars produce energy

Fusion, that is, the merging of atomic cores, is the process by which the sun and the stars produce their energy. It is an ancient dream of mankind to “bring the sun down on earth” and to make use of this energy. Fusion research work in Germany is an integral part of the European fusion research programme and ranges from very basic studies of plasma physics to the realization of technologically demanding components for fusion plants and the construction of the large-scale project “Wendelstein 7-X” in Greifswald.

The sun radiates light because its hydrogen cores are constantly melting in a phased process to become helium cores and thereby release energy. However, the probability of this process is very low despite the considerably high temperature and density inside the sun. On the one hand, this means that fortunately the sun will continue to exist for a very long time. On the other hand, the existing “fuel” quantity in the form of hydrogen is so large that a sufficient amount of energy is continuously released to enable life on earth in spite of the low reaction probability.

The sun’s fusion reactions are too slow under the conditions that can be achieved on earth. Therefore, the fusion of two different kinds of hydrogen cores is to be used here: deuterium and tritium. They are quasi interim steps on the way from hydrogen to helium. Tritium can be derived from lithium under fusion reaction conditions. Deuterium as well as lithium exist in large quantities which means that there will not be a bottleneck for energy production in the case of successful fusion research. The decisive advantage over the present main method of energy production of burning fossil fuels is therefore the avoidance of carbon dioxide emissions on the one hand and the sustained availability of resources on the other. Fusion would therefore complement the increased use of renewable energies, particularly in view of worldwide energy consumption, which will rise significantly over the coming years and decades.

A fusion reaction only occurs if it is possible to overcome the electrical repulsion between the atomic cores involved. In the sun, gravity confines particles with the necessary energy – fast, charged particles, or “ions”, which together with free electrons form a plasma. On earth, such a plasma can only be confined by strong magnetic fields or inertia. Fusion research in Europe focuses on magnetic confinement, while researchers in the US are also studying inertial confinement fusion.

The complexity of the very demanding technologies which are necessary for the realization of the fusion process was underestimated in the early years of fusion research. However, an awareness has developed and efforts are being made to pool the necessary knowledge by means of international cooperation. Thus, fusion research has become a model for international cooperation, which has brought about substantial progress and success in the last decade in particular. An important interim goal was reached: fusion performance of several megawatts, thereby coming very close to the so-called break-even point at which the fusion performance generated in the plasma is equal to the energy needed to start the reaction. These results were achieved primarily at the European JET facility. They are the basis for starting construction of the ITER (“The Way”) international large-scale experiment to study a plasma which generates energy under power plant-like conditions.

In Germany, the Max Planck Institute for Plasma Research (IPP), Garching and Greifswald, as well as the Karlsruhe Institute of Technology and the Research Centre Jülich are working in the field of fusion research. Their work is integrated in the European Fusion Research Programme under Euratom and is coordinated at international level by the International Energy Agency (IEA). The fields of work of the German fusion centres cover everything from demanding basic research in the area of plasma physics to the solution of complex technological issues, and are organized in the Fusion Programme of the Helmholtz Association (HGF) with the following programme topics:

  • ITER – the next step
    Includes all fundamental preliminary physical and technological work for the construction of the next large fusion experiment ITER in international cooperation.
  • Fusion technology
    Includes the development of materials and components which are required for a future power plant (vis-à-vis an experimental reactor).
  • Tokamak physics
    “Tokamak” is a form of magnetic confinement of plasmas which has been researched most extensively worldwide and which is therefore used as a basis for ITER applications. Current Tokamak research tries to record, shape, describe in theoretical terms and directly influence the different conditions a plasma can adopt in this confinement.
  • Stellarator research
    In addition to the Tokamak line, the Stellarator line has been established as a promising confinement concept which allows for continuous operation, in contrast to Tokamak. With “Wendelstein 7-X”, Greifswald is conducting the most advanced experiment of this type worldwide.
  • ASDEX Upgrade, a Tokamak experiment at the IPP which is also being intensively used by other European fusion laboratories.
  • TEXTOR, a Tokamak experiment at the Research Centre Jülich involving the participation of Belgian and Dutch partners.
  • TOSKA, a low-temperature test facility for superconducting magnet coils at Karlsruhe Research Center.
    Karlsruhe Tritium Laboratory (TLK), a unique institution in Europe for handling tritium for procedure development.
  • Wendelstein 7-X, the most significant Stellarator experiment worldwide (under construction).