Method and apparatus for the formation of a spheromak plasma

An apparatus for producing and confining a spheromak plasma, comprising:

• a vacuum chamber having a major axis and an equatorial midplane,
• first coil means for producing a first poloidal magnetic field in said vacuum chamber at a time t.sub.1,
• a ring core having a minor axis surrounding said major axis disposed symmetrically within said vacuum chamber with respect to said equatorial plane and said major axis, said ring core including:
• second coil means for producing a second poloidal vacuum magnetic field in said vacuum chamber at a time t.sub.2 >t.sub.1, said second poloidal vacuum magnetic field being a time-varying field;
• and
• third coil means for producing a time varying toroidal vacuum magnetic field inside said ring core at a time t.sub.3 >t.sub.1, and for initiating in the presence of a gas outside said ring core a plasma discharge in said vacuum chamber outside said ring core;
• said first and second poloidal magnetic fields, when superposed, forming a composite poloidal magnetic field having a strength which is weaker on a radially interior major radius side of said ring core than on a radially exterior major radius side of said ring core, such that said plasma expands into the region of weaker magnetic field;
• and
• means for pinching off a portion of said expanded plasma and for causing reconnection of the magnetic field lines thereof, thereby forming a detached spheromak plasma concentric with, and having a major radius less than the major radius of, said ring core.

A method for producing and confining a spheromak plasma, comprising:

• evacuating a vacuum vessel and filling said vessel with a neutral species,
• producing a first poloidal magnetic field by pulsing a current through a pair of toroidal equilibrium field coils,
• producing a second poloidal magnetic field by pulsing a current through a poloidal field generating coil of a ring core, such that said first and second poloidal magnetic fields are superimposed to form a composite poloidal field having first and second regions, the poloidal field in said second regin being stronger than the poloidal field in said first region,
• producing a toroidal vacuum magnetic field inside said ring core by passing a current through a toroidal field generating coil of said ring core, thereby initiating a plasma discharge in said vacuum vessel outside said ring core and causing toroidal flux to appear outside of said ring core,
• expanding the plasma in the direction of said first region, and
• pinching off a portion of said expanded plasma so as to cause poloidal magnetic field line reconnection within the pinched-off portion, thereby producing a detached spheromak plasma concentric with, and having a major radius less than the majors radius of, said ring core.

An apparatus for producing and confining a spheromak plasma, comprising:

• a vacuum vessel having a major axis and an equatorial midplane;
• equilibrium field coil means for producing an equilibrium magnetic field directed primarily along the major axis;
• a ring core disposed within said vacuum vessel symmetrically with respect to said major axis and said equatorial midplane, and having a minor axis in said equatorial plane wound about said major axis, a major radius and a minor radius, said ring core including a toroidal flux coil surrounding said minor axis and a separate poloidal flux coil and being supported within said vacuum vessel by a plurality of ring supports, said ring supports housing conductors for supplying current to said poloidal and toroidal flux coils;
• means for energizing said equilibrium field coils at a time t.sub.1 to create a first poloidal magnetic field within said vacuum vessel;
• means for energizing said poloidal flux coil at a time t.sub.2 >t.sub.1 to create a second poloidal magnetic field within said vacuum vessel, said first and second poloidal fields being super-imposed to form a composite poloidal field whose strength is greater on a radially exterior major radius side of said ring core, than on a radially interior major radius side of said ring core;
• means for energizing said toroidal flux coil at a time t.sub.3 >t.sub.1 for initiating a plasma discharge within said vacuum vessel, said ring core and said equilibrium field coils being operable to cause said plasma to become expanded and distended toward said major axis;
• and
• means, located on said radially interior side of said ring core, for pinching off a portion of said distended plasma, whereby a detached spheromak plasma is produced.

An apparatus for producing and confining a spheromak plasma, comprising:

• a vacuum chamber having a major axis and an equatorial midplane,
• first coil means for producing a first poloidal magnetic field in said vacuum chamber at a time t.sub.1,
• a ring core having a minor axis surrounding said major axis disposed symmetrically within said vacuum chamber with respect to said equatorial plane and said major axis, said ring core including:
• second coil means for producing a second poloidal vacuum magnetic field in said vacuum chamber at a time t.sub.2 >t.sub.1, said second poloidal vacuum magnetic field being a time-varying field;
• and
• third coil means operative for producing a time varying toroidal magnetic field inside said ring core at a time t.sub.3 >t.sub.1, and for initiating in the presence of a gas a plasma discharge in said vacuum chamber;
• said first and second poloidal magnetic fields, when superimposed, forming a composite poloidal magnetic field having a strength which is weaker on a radially interior major radius side of said ring core than on a radially exterior major radius side of said ring core, such that said plasma expands into the region of weaker magnetic field;
• and
• means, located on said radially interior side of said ring core, for pinching off a portion of the expanded plasma and for causing reconnection of the magnetic field lines thereof, thereby forming a detached spheromak plasma.

A method for producing and confining a spheromak plasma, comprising:

• evacuating a vacuum vessel and filling said vessel with a neutral species;
• producing a first poloidal magnetic field by pulsing a current through a pair of toroidal equilibrium field coils;
• producing a second poloidal magnetic field by pulsing a current through a poloidal field generating coil of a ring core, such that said first and second poloidal magnetic fields are superimposed to form a composite poloidal field having first and second regions, the poloidal field in said second region being stronger than the poloidal field in said first region;
• producing a toroidal magnetic field inside said ring core by passing a current through a toroidal field generating coil of said ring core, thereby initiating a plasma discharge and causing toroidal flux to appear outside of said ring core;
• expanding the plasma in the direction of said first region;
• and
• pinching off a portion of said expanded plasma with a pinching coil located in said first region so as to cause poloidal magnetic field line reconnection within the pinched-off portion, thereby producing a detached spheromak plasma.