The Polywell: A Spherically Convergent Ion Focus Concept

The Polywell spherically convergent ion focus concept for controlled thermonuclear fusion is described. The device magnetically confines electrons by a quasi sphericalcusp magnetic field, forming a potential well. Ions are electrostatically confined by this well, converg ing to a dense focus in the center of the spherical poten tial, where the fusion rate is large because of the high local density of transient energetic ions. Power balance and critical physics issues are outlined, along with cur rent experimental and theoretical work. The potential of the device for D3He operation is described by the derivation of scaling laws for energy gain. I