Secondly: Feed the coils

• External Links
• Tore Supra
• LHD
• EAST
• KSTAR
• Wendelstein 7-X
• ITER

JET's coils and plasma

Plasma heating is not the biggest consumer of energy at JET. At the hundreds of million degrees Celsius needed, standard thermal insulation methods are totally inadequate. The reason tungsten is the material with the highest known melting point of 3,422 degree Celsius, which isn’t at all sufficient to resist the high temperature of the plasma. So to confine the plasma JET uses a magnetic confinement system to keep the charged particles of the plasma away from the vessel wall and to protect it from the hot plasma. Unless the plasma is well insulated in the magnetic field, it can lose energy due to a temperature gradient from the vessel wall to the plasma centre of about one million degrees per centimetre. The well-defined magnetic coils producing the strong magnetic fields need a significant amount of power. Under the circumstances high currents normally required, electrical resistance of the coils causes significant losses of energy in form of heat. As a consequence they need to be water-cooled. The energy to do so is mostly dissipated to the atmosphere via special cooling towers.

Some fusion experiments, like Tore Supra in France, LHD in Japan, EAST in China, KSTAR in South Korea,Wendelstein 7-X (under construction) in Germany, or the future experiment ITER use superconducting coils that avoid energy losses at the expense of running them at very low temperatures, around -270 degree Celsius, using liquid helium. These experiments will run with higher energy efficiency by using superconducting coils.