Spherical torus

MAGNETIC TOPOLOGY The spherical torus is a tokamak with a minimal "hole" through it, achieved by eliminating the solenoid magnetic coils, normally located there, that induce current in the plasma. The resulting low aspect ratio (major-to-minor plasma radius) plasma has performance advantages but requires a separate means to produce toroidal plasma cur- rent. Also, the legs of each toroidal field coil pass through the hole and are subjected to intense neutron radiation, so that superconducting mag- nets must be avoided.

• Small size and
  low cost.
• Low magnetic
  field and power.
• High ratio of
  plasma pressure
  to magnetic field
  pressure.
• Ease of mainte-
  nance (the magnets
  can be jointed).

• Columbia University, New York.
• General Atomics, California.
• Oak Ridge National Laboratory, Tennessee.
• Princeton Plasma Physics Laboratory, New Jersey.
• University of Washington.
• University of Wisconsin.
• UKAEA Culham Laboratory, United Kingdom.
• University of Tokyo and Waseda University, Japan.
• loffe Physical-Technical Institute, Russia.
• Institute de Pesquisas Espocias, Brazil.