A 140‐kJ theta‐pinch device originally constructed for spectroscopic investigations of highly ionized atoms is described. Atoms of solid elements are introduced into the initial plasma by laser‐driven ablation from solid targets. The stability of the field‐reversed plasma configuration is investigated with and without impurities. An inhomogeneous impurity distribution leads to the ejection of the plasma as a whole. This phenomenon is interpreted as the result of asymmetric field line reconnection at the ends.