Reaktor Fusi

Reaktor Fusi

Diagnostics

About 50 individual measurement systems will help to control, evaluate and optimize plasma performance in ITER and to further understanding of plasma physics.

An extensive diagnostic system will be installed on the ITER machine to provide the measurements necessary to control, evaluate and optimize plasma performance in ITER and to further the understanding of plasma physics. These include measurements of temperature, density, impurity concentration, and particle and energy confinement times.

A Bolometer Camera developed at JET. Photo courtesy:K McKormick (IPP,Garching), A Huber (FZK)

The system will comprise about 50 individual measuring systems drawn from the full range of modern plasma diagnostic techniques, including lasers, X-rays, neutron cameras, impurity monitors, particle spectrometres, radiation bolometers, pressure and gas analysis, and optical fibres.

Because of the harsh environment inside the Vacuum Vessel, these systems will have to cope with a range of phenomena not previously encountered in diagnostic implementation, while all the while performing with great accuracy and precision. The levels of neutral particle flux, neutron flux and fluence will be 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 - will be about 100 times longer.

Reaktor Fusi

Reaktor Fusi

Vacuum Vessel

The large stainless steel Vacuum Vessel provides an enclosed, vacuum environment for the fusion reaction.

A cut-away of the ITER Vacuum Vessel showing the Blanket modules attached to its inner wall and the Divertor at the bottom.

The Vacuum Vessel is a hermetically-sealed steel container inside the Cryostat that houses the fusion reaction and acts as a first safety containment barrier. In its doughnut-shaped chamber, or torus, the plasma particles spiral around continuously without touching the walls.

The size of the Vacuum Vessel dictates the volume of the fusion plasma; the larger the vessel, the greater the amount of power that can be produced. The ITER Vacuum Vessel will be twice as large and sixteen times as heavy as any previous tokamak, with an internal diametre of 6 metres. It will measure a little over 19 metres across by 11 metres high, and weigh in excess of 5000 tons.

The ITER Vacuum Vessel with its 44 ports. At 8000 tons, the stainless steel vacuum vessel weighs slightly more than the Eiffel Tower.

The Vacuum Vessel will



have double steel walls, with passages for Cooling Water to circulate between them. The inner surfaces of the Vessel will be covered with Blanket Modules that will provide shielding from the high-energy neutrons produced by the fusion reactions. Some of the Blanket Modules will also be used at later stages to test materials for Tritium Breeding concepts.

Forty-four ports will provide access to the Vacuum Vessel for Remote Handling operations, Diagnostic systems, Heating, and Vacuum systems: 18 upper ports, 17 equatorial ports, and 9 lower ports.

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Web Resmi ITER

Reaktor Fusi

Reaktor Fusi

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.

Toroidal Field System

One of the 18 Toroidal Field coils.

The 18 Toroidal Field (TF) magnets produce a magnetic field around the torus, whose primary function is to confine the plasma particles. The ITER TF coils are designed to have a total magnetic energy of 41 gigajoules and a maximum magnetic field of 11.8 tesla. The coils will weigh 6540 tons total; besides the Vacuum Vessel, they are the biggest components of the ITER machine.

The coils will be made of Cable-In-Conduit superconductors, in which a bundle of superconducting strands is cabled together and cooled by flowing Helium, and contained in a structural jacket. The strands necessary for the ITER TF coils have a total length of 150.000 kilometres and would span the earth more than three times.

Poloidal Field System

The Poloidal Field coil system consists of six independent coils placed outside the Toroidal Magnet structure.

The Poloidal Field (PF) magnets pinch the plasma away from the walls and contribute in this way to maintaining the plasma's shape and stability. The PF field is induced both by the Magnets and by the current drive in the plasma itself.

The Poloidal Field coil system consists of six horizontal coils placed outside the Toroidal Magnet structure. Due to their size, the actual winding of five of the six PF coils will take place in a dedicated, 250-metre long coil winding building on the ITER site in Cadarache. The smallest of the PF coils will be manufactured offsite and delivered finished.

The ITER PF coils are also made of Cable-in-Conduit conductors. Two different types of strands are used according to operating requirements, each displaying differences in high-current and high-temperature behaviour.

Central Solenoid

The Central Solenoid - the backbone of the Magnet system - is essentially a large transformer.

The main plasma current is induced by the changing current in the Central Solenoid which is essentially a large transformer, and the 'backbone' of the Magnet System. It contributes to the inductive flux that drives the plasma, to the shaping of the field lines in the Divertor region, and to vertical stability control. The Central Solenoid is made of six independent coil packs that use a Niobium-Tin (Nb3Sn) Cable-in-Conduit superconducting conductor, held together by a vertical precompression structure. This design enables ITER to access a wide operating window of plasma parameters, enabling the testing of different operating scenarios up to 17 MA and covering inductive and non-inductive operation.

Each coil is based on a stack of multiple pancake winding units that minimizes joints. A glass-polyimide electrical insulation, impregnated with epoxy resin, gives a high voltage operating capability, tested up to 29 kV. The conductor jacket material has to resist the large electromagnetic forces arising during operation and be able to demonstrate good fatigue behaviour. The conductor will be produced in unit lengths up to 910 metres.

Sumber:

Web Resmi ITER