Record Breakers

 A poloidal coil is inserted into the Tokamak Pit. (Credit © ITER Organization, http://www.iter.org/)

A poloidal coil is inserted into the Tokamak Pit.

Being the largest tokamak ever built, the ITER is a record holder in many ways. First, because of its size. At 19.4 metres across and 11.4 metres high, the vacuum vessel will be the biggest in the world. Its interior volume will be 1,400 m³ and weigh approximately 5,200 tonnes. The plasma volume of 830 m3 will surpasses by more than eight times the plasma volume of the largest operating tokamak, the JET. If the planned temperature of 150 million Kelvin is reached, the ITER plasma core will be the hottest place for light years around, making it a record in the whole solar system. The vacuum vessel is encompassed by cryostat with a volume of 16,000 m3 one of the biggest evacuated spaces on the Earth. Inside the cryostat, the hottest and coldest places in the Solar system meet at a distance of only a few metres. The hottest is 150,000,000 °C plasma, the coldest is superconducting coils cooled to −269 °C. For their winding 100,000 kilometres of niobium-tin superconducting strands were manufactured. Each toroidal coil weights 310 tons and is 17 metres high. The poloidal coils are even bigger. The greater one is a ring with a diameter of 24 metres and is so big that it could not be transported and a special winding facility was built on the ITER site where the poloidal coils were manufactured. The greatest magnetic field will be generated by the central solenoid. 13 Tesla will produce such strong electromagnetic forces that it will try to tear it apart with twice the power of a Space shuttle lift-of. Another comparison to the Space shuttle experience is the heat load on the first wall that will be directly facing the hot plasma. The heat that it will have to withstand is about ten times greater than the one to which a spacecraft descending through the atmosphere is exposed to. The power resulting from D-T fusion reaction is supposed to be 500 M, returning 10 times more energy than will be used for the heating, which means for a first time Q greater than 1, in this case Q = 10. The previous record holder is tokamak JET with 16 MW of fusion power and Q = 0.67. Total weight of the ITER machine will be 23,000 tons which is the weight of three Eiffel Towers.

Without dispute the ITER is the most ambitious, the most technically challenging, the most complicated, the most demanding on cooperation and the most costly project ever to be undertaken. The estimated cost of the ITER is more than €22 billion.