Double layer field shaping systems for toroidal plasmas

Apparatus for generation and confinement of a toroidal plasma of noncircular cross section having major and minor toroidal axes, with the plasma being elongated in the direction of the major toroidal axis, comprising

• means for providing a toroidal magnetic field for plasma confinement in a plasma confinement zone,
• means for providing a toroidal current in the plasma for generation of a poloidal magnetic field,
• a field shaping coil system for shaping the plasma cross section to stabilize the plasma and axisymmetrically with respect to the major toroidal axis to elongate the plasma in a direction along the major toroidal axis comprising an inner stabilizing coil system having a coil layer comprising a plurality of inner S coil elements aligned to conduct in a direction generally along the direction of the minor toroidal axis and disposed adjacent to and surrounding the plasma confinement zone with a physical contour generally corresponding to the desired elongated outer contour of the plasma, and an outer field shaping coil system having a coil layer comprising a plurality of outer coil elements aligned to conduct in a direction generally along the direction of the minor toroidal axis and being separated from the disposed exteriorly of the inner coil layer
• the electrical currents I.sub.S of said inner coil elements and the electrical currents I.sub.F of said outer coil elements being related in each of the coil elements as follows:
• ##EQU6## where I.sub.S.sup.j is the current in the jth S coil element, I.sub.F.sup.j is the current in the jth F coil element, I.sub.F.sup.j is the current in the jth F coil element for which all S coil electrical currents are zero, M.sub.SF.sup.ij is the mutual inductance between the ith S coil element and the jth F coil element, and M.sub.SS.sup.ij is the mutual inductance between the ith S coil element and the jth S coil element and,
• programming means for controlling the currents in the F coil elements of said outer coil layer to minimize the currents I.sub.S.sup.j in the S coil elements of the inner coil layer during plasma generation and confinement.