Helical plasma structure observed in a hard-core theta pinch

Through the addition of an axial current-carrying conductor (hard core), helical fields and magnetic shear have been added to the elongated toroidal plasma generated in a θ-pinch device operated with antiparallel bias field. Two-dimensional (r, z) photographs indicate the presence, from the beginning of the discharge, of a persistent luminous helical structure imbedded in the annular plasma.