ASDEX upgrade

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ASDEX upgrade: model

ASDEX Upgrade is one of the two largest German experimental facilities currently in operation for the development of fusion reactors (the other is Wendelstein 7-X ). It is located in the Max Planck Institute for Plasma Physics in Garching near Munich and is of the tokamak type. The first plasma was generated in 1991. Since then (as of 2016) over 30,000 tests have been carried out.

ASDEX Upgrade examines questions of plasma physics that are important for the ITER fusion experiment, which is currently under construction, and thus for future electricity generation in nuclear fusion power plants. The behavior of plasma from deuterium is examined . The deuterium- tritium mixture required to generate a significant amount of power is not yet used.

ASDEX Upgrade is the successor to the older ASDEX system ( Axially Symmetrical Divertor Experiment ) and is of medium size in international comparison to other tokamaks. The system has a radius of 5 meters and a total weight of 800 tons. The plasma can be heated with up to 27 megawatts. Are available for addition to the ohmic heating by the plasma stream (about 1 MW) a neutral particle (up to 20 MW) and heating with electromagnetic waves of suitable frequencies : ion - and electron - cyclotron resonance (each of up to 6 MW).

Lining the vessel wall

During operation, atoms are inevitably removed from the wall material of the plasma vessel by sputtering , ionized and contaminated the plasma. Such an impurity is fundamentally more disturbing, the more electrons its atom contains, i.e. the higher its atomic number Z is. For this reason, materials with the lowest possible atomic number were initially considered the best choice for wall cladding. Since the lining should also have a high melting temperature, graphite ( Z = 6) was chosen for many systems .

ASDEX Upgrade, on the other hand, is completely coated on the inside with tungsten ( Z = 74). Tungsten also has a very high melting point of over 3000 ° C, so it can withstand high temperatures. Tungsten is expected to take up less tritium compared to graphite in a deuterium-tritium powered fusion reactor, which is desirable because of the radioactivity of tritium. In ASDEX Upgrade it could be shown that the tungsten concentration in the plasma can be kept low enough even with a pure tungsten wall with good retention capacity of the divertor .

Technical specifications

Technical data reactor
maximum magnet flux density: 3.9 tesla
Plasma flow: 0.4 to 1.6 mega amps
Large plasma radius: 1.65 meters
Small plasma radius: 0.5 meters
Elongation (plasma height / width): 0.8 / 0.5 = 1.6
maximum pulse duration: 10 seconds
Plasma heating: 27 megawatts
Plasma volume: 14 cubic meters
Plasma amount: 3 milligrams
Plasma temperature: over 100 million Kelvin

history

ASDEX Upgrade was conceived from 1981 as a follow-up experiment to ASDEX. After the divertor concept had been successfully tested in ASDEX , ASDEX Upgrade should investigate this concept for a reactor-relevant geometry: In a reactor, the space inside the toroidal field coils must be used as well as possible for generating the hot plasma, i.e. the magnetic coils for generating the divertor configuration must be outside of the magnetic fields of the toroidal field coils. The orientation towards a divertor suitable for a reactor, including the investigations into particle and power dissipation, was not a matter of course in 1980/81, considering that the other three tokamaks planned at the time ( JET , Torus-2, FTU) were to be operated without a divertor. The decision in favor of a divertor was significantly influenced by the IPP's collaboration in concept studies for the (not built) systems NEXT (next european torus) and INTOR (international torus). The decision has proven to be correct; JET was converted from a limiter tokamak into a divertortokamak. In March 1982 the concept for the ASDEX follow-up experiment ASDEX Upgrade was submitted to the European Commission for assessment and funding. In this first phase, three variants were examined: a conversion of the ASDEX, a new building with partially superconducting coils and a new building with normally conductive, water-cooled copper coils. The latter concept received positive reviews, and a detailed project study appeared in 1983, which already presents essential technical details. After their implementation, the first technical systems could be put into operation in 1990. In March 1991 the first plasma discharge was generated.

Web links

Individual evidence

  1. ↑ http://www.aug.ipp.mpg.de/cgibin/local_or_pass/journal.cgi?shot=30000
  2. ↑ https://www.ipp.mpg.de/987591/AUG_deutsch.pdf (accessed on April 21, 2020)
  3. ↑ IPP-Report IPP 1/197, March 1982, "ASDEX-Upgrade - Definition of a tokamak experiment with a reactor compatible poloidal divertor"
  4. ↑ IPP-Report IPP 1/217, May 1983, "ASDEX - UG - ASDEX Upgrade Project Proposal"

Coordinates: 48 ° 15 ′ 43.2 "  N , 11 ° 40 ′ 33.6"  E