ASDEX upgrade: A poloidal divertor tokamak adapted to reactor requirements

Abstract ASDEX Upgrade, a medium-size tokamak, is characterized by the following features: a poloidal field system with all coils located outside the TF magnet; elongated plasmas up to s = 1.6 in double-null (DN), single-null (SN) or limiter-controlled (L) configurations; a plasma current of up to I p ≈ 2 MA, which ensures reactor-like plasma boundary parameters; auxiliary heating (probably ICRH, 12 MW, 8 antennae) producing a reactor-equal energy flux density of 0.3 MW/m 2 in the plasma boundary. The vacuum vessel installation is primarily adapted to SN divertor operation using two toroidal divertor plate arrays ≈ 3 m 2 in area each. It allows DN divertor operation with reduced parameters. Proper adjustment of target plates, antennae and heat shields also allows full-parameter DN and L configurations to be studied. The aims of ASDEX Upgrade are to study the reactor-compatible open divertor configuration in the high-recycling, low-boundary-temperature regime. Boundary layer models promise adequate solutions for taking the plasma energy to the material structure in such a way that impurity production is kept sufficiently low and that proper steady-state plasma conditions can prevail. The condition for helium pumping can also be studied. The detailed design of the tokamak system is about to be completed; the first components have been ordered and construction work is scheduled for completion by the end of 1987.