ITERITER

In ITER, magnetic fields, heating systems and diagnostics are used to confine a Deuterium-Tritium (DT) plasma in a large donut-shaped vacuum vessel with the view to establish the conditions for nuclear fusion and to study and control a “burning plasma.” The temperatures inside the ITER Tokamak must reach 150 million° Celsius in order for the gas in the vacuum chamber to reach the plasma state and for the fusion reaction to occur. The hot plasma must then be sustained at these extreme temperatures in a controlled way in order to extract energy.
The key-objective of ITER is to establish stable plasmas with limited heating from the external sources in which the energy of the helium nuclei (produced by the fusion reaction) is efficiently transfered to the D and T particles. This alpha-particle heating should be enough to maintain the temperature of the plasma.
The ITER Tokamak will rely on three sources of additional heating, Electon Cyclotron Heating, Ion Cyclotron heating and neutral beam injection to provide the input heating power of 50 MW required to bring the plasma to the temperature necessary for fusion.
As an experimental machine, ITER will be equipped with a large array of diagnostic instruments to provide the measurements necessary to control, evaluate and optimize plasma performance in ITER and to further the understanding of plasma physics. Because of the harsh environment inside the vacuum vessel, these systems will cope with a range of phenomena not previously encountered in diagnostic implementation, while performing with great accuracy and precision. The levels of neutral particle flux, neutron flux and fluence are respectively about 5, 10 and 10,000 times higher than the harshest experienced in today's machines. The pulse length of the fusion reaction—or the amount of time the reaction is sustained—is about 100 times longer. Magnetic diagnostics provide input into the determination of the magnetic equilibrium; measure currents in the plasma or in structures; measure plasma stored energy; and control plasma shape and position. Neutron diagnostics such as neutron cameras, neutron spectrometers and neutron flux monitors provide robust measurements of fusion power. Optical systems (Thomson Scattering systems and interferometers) are used to measure temperature and density profiles at the core or the edge of the ITER plasma. Bolometric systems situated all around the vacuum vessel furnish information on the spatial distribution of radiated power in the main plasma and divertor region using sparse-data tomography. Spectroscopic instruments and neutral particle analyzers are installed to cover the visible to X-ray wavelength range, delivering information on plasma parameters such as impurity species and density, input particle flux, ion temperature, helium density, fuelling ratio, plasma rotation, and current density. Microwave diagnostics probe the main plasma and the plasma in the divertor region in order to measure plasma position. Plasma-facing and operational diagnostics aid in the protection and operation of the machine. Several wide/angle visible and infrared viewing systems will be dedicated to monitoring the conditions in the main chamber and the divertor (divertor target temperature, pressure, residual gas analyzers, and erosion, dust and tritium monitoring).
In addition to the scientific mission, ITER has an engineering mission: to demonstrate key technology for DEMO. This entails a very diverse programme, on topics such a remote handling, plasma control, tritium breeding, and magnet technology. ITER is a driver of new technology. As a few superlatives: the site features the largest cryo-stat, haptic master-slave system, and super conduction coils on earth.