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ITER: the world's largest Tokamak

ITER

ITER is a large international fusion experiment aimed at demonstrating the scientific and technological feasibility of fusion energy.

 

ITER (Latin for "the way") will play a critical role advancing the worldwide availability of energy from fusion — the power source of the sun and the stars.

 

To produce practical amounts of fusion power on earth, heavy forms of hydrogen are joined together at high temperature with an accompanying production of heat energy. The fuel must be held at a temperature of over 100 million degrees Celsius. At these high temperatures, the electrons are detached from the nuclei of the atoms, in a state of matter called plasma.

 

In magnetic fusion energy, such as will be studied in ITER, magnetic fields are used to confine the high-temperature plasma with a density typical

 

An unprecedented international collaboration of scientists and engineers has performed needed research and development and designed a burning plasma experiment called ITER. The fusion power produced by ITER will be 10 times greater than the external power delivered to heat the plasma.

 

The United States has joined the other ITER partners in negotiations for construction of this project, whose mission is to demonstrate the scientific and technological feasibility of fusion power. These deliberations could lead to the operation of ITER around the middle of the next decade.

 

ITER Partners are The People's Republic of China, the European Union (represented by Euratom), India, Japan, the Republic of Korea, the Russian Federation, and the United States of America. The device will be built at Cadarache located near Marseille in the Provence-Alpes_Cote d'Azur region of southeastern France.

 

ITER: the world's largest Tokamak

 

ITER is based on the 'tokamak' concept of magnetic confinement, in which the plasma is contained in a doughnut-shaped vacuum vessel. The fuel—a mixture of Deuterium and Tritium, two isotopes of Hydrogen—is heated 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; these are produced by superconducting coils surrounding the vessel, and by an electrical current driven through the plasma.

 

Magnets

The 48 elements of the ITER Magnet system will generate a magnetic field some 200,000 times higher than that of our Earth.

The ITER Magnet System comprises 18 superconducting Toroidal Field and 6 Poloidal Field coils, a Central Solenoid, and a set of Correction coils that magnetically confine, shape and control the plasma inside the Vacuum Vessel. Additional coils will be implemented to mitigate Edge Localized Modes (ELMs), which are highly energetic outbursts near the plasma edge that, if left uncontrolled, cause the plasma to lose part of its energy.

 

Superconducting cable being spooled after production at ASIPP, Institute for Plasma Physics, Hefei, China. Photo: Peter Ginter



The power of the magnetic fields required to confine the plasma in the ITER Vacuum Vessel is extreme. For maximum efficiency and to limit energy consumption, ITER uses superconducting magnets that lose their resistance when cooled down to very low temperatures. The Toroidal and Poloidal Field coils lie between the Vacuum Vessel and the Cryostat, where they are cooled and shielded from the heat generating neutrons of the fusion reaction.

 

The superconducting material for both the Central Solenoid and the Toroidal Field coils is designed to achieve operation at high magnetic field (13 Tesla), and is a special alloy made of Niobium and Tin (Nb3Sn). The Poloidal Field coils and the Correction coils use a different, Niobium-Titanium (NbTi) alloy. In order to achieve superconductivity, all coils are cooled with supercritical Helium in the range of 4 Kelvin (-269°C). Superconductivity offers an attractive ratio of power consumption to cost for the long plasma pulses envisaged for the ITER machine.

 


Date: 2016-03-03; view: 831


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