Wednesday, December 16, 2015

Mimicking The Sun - Wendelstein 7-X Helium Plasma Fusion

Fusion at 150 million degrees, promising cheap,
almost inexhaustible supply of energy
Max Planck Institute for Plasma Physics (Dec 10, 2015) - The first test of the "stellarator" has been carried out with the Wendelstein 7-X fusion device producing helium plasma. A breakthrough, according to the press release. However, horrendously expensive fusion technology and the promise for future cheap, limitless and clean energy have been entertained ever since the 1950s. Still physicists are in a worldwide race to create stable fusion devices that could not only mimic the Sun but release abundant energy, without the volumes of toxic waste generated by nuclear fission. This time around it took scientists from the Max Planck Institute for Plasma Physics in Greifswald, Germany, nine years to build the EUR 1.1 billion machine, and they have spent over a year preparing for the test. Another milestone? Fusion involves placing hydrogen atoms under high heat and pressure until they fuse into helium atoms. When Deuterium and Tritium nuclei - which can be found in hydrogen - fuse, they form a helium nucleus, a neutron and a lot of energy. This is done by heating the fuel to temperatures in excess of 150 million°C, forming a hot plasma. Strong magnetic fields are used to keep the plasma away from the walls so that it doesn't cool down and loses its energy potential. These are produced by superconducting coils surrounding the vessel, and by an electrical current driven through the plasma. For energy production plasma has to be confined for a sufficiently long period for fusion to occur. Europe has a large track record in fusion: Europe’s JET (Joint European Torus) located at Culham (UK) is the world’s largest fusion facility and was so far the only one capable of working with a Deuterium-Tritium fuel mixture. Reportedly JET has reached all its originally planned objectives and in some cases surpassed them. In 1997 it achieved a world record fusion power production of 16 MW and a Q = 0.65. Europe has also been building on the knowledge accumulated through the Tore Supra tokamak in France, the first large tokamak to use superconducting magnets; the ASDEX device in Germany with ITER-shaped plasmas; the reversed pinch device RFX in Italy and the stellarators TJ-II in Spain and the W7-X in Germany.