ASDEX Upgrade

An important topic for ASDEX Upgrade is the interaction between the plasma and the confining walls. This entails, on the one hand, damage to the wall of the plasma vessel and, on the other, undesirable contamination of the plasma. To counteract these effects, ASDEX Upgrade is being used to investigate a special magnetic field configuration known as the divertor. The divertor removes the outer boundary layer of the plasma away from the hot core and deposits it on collector plates. This process rids the plasma of disturbing impurities, which simultaneously safeguards the wall of the plasma vessel and achieves good thermal insulation of the fuel.

The strong coupling of the plasma core in ASDEX Upgrade with the conditions at the plasma edge makes it possible to optimise the plasma core from the edge and improve confinement. In addition, modes of operation in which the profile of the plasma current is influenced (advanced tokamak) are investigated for their compatibility with the divertor. For this purpose an auxiliary plasma current is produced with high-frequency waves or particle injection. Depending on the current profile, a transport barrier can form which greatly reduces plasma losses to the outside and improves the values in the plasma core. ASDEX Upgrade will attempt to create such conditions in divertor operation for the first time in quasi-steady state (i.e. for a few seconds).

Objectives of ASDEX Upgrade

• divertor studies
  
• plasma edge physics
  
• particle and energy transport in the plasma core
  
• plasma instability studies
  
• testing of theoretical models in divertor physics; turbulence and plasma transport
  
• advanced tokamak studies