Magnetic mirror minimum B field with optimal ellipticity.

Closed form expressions for the ellipticity and the magnetic field of a conventional mirror machine, constrained to fulfill a minimum B stability criterion, are derived. The best result for zero-β plasmas is obtained with a marginally stable magnetic field, and the ellipticity is 13.9 with the representative value 4 for the mirror ratio. The gyro centers move on a single filed line, and thereby the perpendicular drift is zero and the radial transport is minimized. The flux tube has quadrupolar symmetry with straight (nonparallel) field lines in the confinement region. [ABSTRACT FROM AUTHOR]