Researchers imitate plasma conditions of nuclear fusion reactor ITER
Researchers at the FOM Institute for Plasma Physics Rijnhuizen in Nieuwegein have been succeeded in imitating the plasma conditions that are expected to be occurring in future nuclear fusion reactors like ITER by experimenting in the laboratory Pilot-PSI. This is an important breakthrough in the research of the interaction between hydrogen plasma and reactor walls. They will soon have their findings published in the scientific journal Applied Physics Letters.
ITER is the next step to international nuclear fusion research. Its purpose is to demonstrate the scientific and technical feasibility of nuclear fusion being a clean, safe and inexhaustible source of energy. ITER has to prove that it is possible to generate long-lasting energy with nuclear fusion. In the fusion reactor light nuclei (isotopes of hydrogen) are fusing together and much energy is being released. The fusion process takes place at an extremely high temperature of 150 million degrees. It is at such high temperatures that matter forms a plasma, a warm gas of charged particles. A plasma may be locked in a ring-shaped reactor. Magnetic fields hold the plasma in there. The energy that is being released at the fusion reaction may be used for generating electricity or, say, for producing hydrogen. ITER has been designed to generate about five hundred megawatts for ten minutes, ten times as much as is being used for preserving the warm fusion plasma.
The load of reactor walls
The walls of nuclear fusion reactor ITER will be exposed to an unprecedentedly intense flow of hydrogen plasma. The hydrogen plasma erode the wall and causes piling of fuel in the wall material. This may stand a long operational management of the reactor in the way. Many of the physical and chemical processes that determine the interaction between hydrogen plasma and walls are still not understood. The unprecedentedly high intensity of the plasma causes a so-called 'strongly coupled regime': through the interaction between plasma and wall particles arise that are being inserted in the plasma. The reactor wall is also exposed to this. This 'strongly coupled regime' will determine the interaction between plasma and wall in ITER as well.
In the PSI-laboratory at the FOM Institute Rijnhuizen in Nieuwegein researchers are conducting a unique research in order to obtain access to this terra incognita. The so-called cascaded arc, an electric current through a gas mixture, forms plasma. By having this process taken place in a strong magnetic field, the researchers were able to form a plasma that has a record density. This plasma causes a wall load of ten megawatts per square metre. The future fusion reactor ITER is expected to have similar conditions. By way of comparison: at the surface of the sun its density of power is only five times higher.
Unexpectedly high
The researchers achieved the unexpectedly high efficiency of the plasma source and high temperature of the plasma by cleverly combining the magnetic field and an optimized nozzle. They explained that the extra heating arises, because the plasma flow intersects the magnetic field outside the nozzle. The findings are highly important to research on the interaction between hydrogen plasma and reactor walls. The researchers are now able to test various materials under ITER-conditions by using this plasma source.
For more information, please contact Gerard van Rooij, FOM Institute for Plasma Physics Rijnhuizen in Nieuwegein, phone: +31 (0)30 609 67 44.
For more information on nuclear fusion, see www.fusie-energie.nl.