ASDEX Upgrade
Encyclopedia
ASDEX Upgrade is a divertor tokamak
, that went into operation at the Max-Planck-Institut für Plasmaphysik
, Garching in 1991. At present, it is Germany
's largest fusion
experiment.
properties, particularly the plasma density and pressure and the wall load, have been adapted in ASDEX Upgrade to the conditions that will be present in a future fusion power plant.
ASDEX Upgrade is, compared to other international tokamaks, a midsize tokamak experiment. It began operation in 1991 and it succeeds the ASDEX experiment, which was in operation from 1980 until 1990.
One innovative feature of the ASDEX Upgrade experiment is its all-tungsten
first wall; tungsten is a good choice for the first wall of a tokamak because of its very high melting point
(over 3000 degrees Celsius) which enables it to stand up to the very high heat fluxes emanating from the hot plasma at the heart of the tokamak; however there are also problems associated with a tungsten first wall, such as tungsten's tendency to ionise at high temperatures, "polluting" the plasma and diluting the deuterium
-tritium
fuel mix. Furthermore, as a high Z material, radiation from fully ionized tungsten in the plasma is several orders of magnitude higher than that of other proposed first wall components such as carbon fibre composites (CFCs) or beryllium. This result allows for far less tungsten to "contaminate" a proposed break-even plasma. ASDEX Upgrade will examine ways to overcome this problem, in preparation for the construction of ITER
's first wall.
The experiment has an overall radius of 5 metres, a gross weight of 800 metric tons, a maximum magnetic field strength of 3.1 tesla
, a maximum plasma current of 1.6 megaampere
and maximum heating power of up to 27 megawatt
. Plasma heating and current drive in the ASDEX Upgrade is derived from several sources, namely 1 MW of ohmic heating, 20 MW of neutral beam injection
, 6 MW via ion cyclotron resonance
heating (ICRH) at frequencies between 30 and 120 megahertz
, and 2 x 2 MW of electron cyclotron resonance
heating (ECRH) at 140 gigahertz
. It has 16 toroidal field coils and 12 poloidal field coils.
Tokamak
A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...
, that went into operation at the Max-Planck-Institut für Plasmaphysik
Max-Planck-Institut für Plasmaphysik
The Max-Planck-Institut für Plasmaphysik is a physics institute for the investigation of plasma physics, with the aim of working towards fusion power...
, Garching in 1991. At present, it is Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
's largest fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
experiment.
Overview
To make experiments under reactor-like conditions possible, essential plasmaPlasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
properties, particularly the plasma density and pressure and the wall load, have been adapted in ASDEX Upgrade to the conditions that will be present in a future fusion power plant.
ASDEX Upgrade is, compared to other international tokamaks, a midsize tokamak experiment. It began operation in 1991 and it succeeds the ASDEX experiment, which was in operation from 1980 until 1990.
One innovative feature of the ASDEX Upgrade experiment is its all-tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
first wall; tungsten is a good choice for the first wall of a tokamak because of its very high melting point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
(over 3000 degrees Celsius) which enables it to stand up to the very high heat fluxes emanating from the hot plasma at the heart of the tokamak; however there are also problems associated with a tungsten first wall, such as tungsten's tendency to ionise at high temperatures, "polluting" the plasma and diluting the deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
-tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
fuel mix. Furthermore, as a high Z material, radiation from fully ionized tungsten in the plasma is several orders of magnitude higher than that of other proposed first wall components such as carbon fibre composites (CFCs) or beryllium. This result allows for far less tungsten to "contaminate" a proposed break-even plasma. ASDEX Upgrade will examine ways to overcome this problem, in preparation for the construction of ITER
ITER
ITER is an international nuclear fusion research and engineering project, which is currently building the world's largest and most advanced experimental tokamak nuclear fusion reactor at Cadarache in the south of France...
's first wall.
The experiment has an overall radius of 5 metres, a gross weight of 800 metric tons, a maximum magnetic field strength of 3.1 tesla
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
, a maximum plasma current of 1.6 megaampere
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
and maximum heating power of up to 27 megawatt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
. Plasma heating and current drive in the ASDEX Upgrade is derived from several sources, namely 1 MW of ohmic heating, 20 MW of neutral beam injection
Neutral Beam Injection
To initiate a sustained fusion reaction, it is usually necessary to use many methods to heat the plasma, including RF heating, electron cyclotron resonance heating , ion cyclotron resonance heating , and neutral beam injection....
, 6 MW via ion cyclotron resonance
Ion cyclotron resonance
Ion cyclotron resonance is a phenomenon related to the movement of ions in a magnetic field. It is used for accelerating ions in a cyclotron, and for measuring the masses of an ionized analyte in mass spectrometry, particularly with Fourier transform ion cyclotron resonance mass spectrometers...
heating (ICRH) at frequencies between 30 and 120 megahertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, and 2 x 2 MW of electron cyclotron resonance
Electron cyclotron resonance
Electron cyclotron resonance is a phenomenon observed both in plasma physics and condensed matter physics. An electron in a static and uniform magnetic field will move in a circle due to the Lorentz force...
heating (ECRH) at 140 gigahertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
. It has 16 toroidal field coils and 12 poloidal field coils.