Abstract: An interrupted annular solenoid activator for use in well or subsea tools is provided. An interrupted annular armature member of a ferromagnetic material has a wire coil wound about it. A separate curved annular segment of the generally toroidally shaped armature is mounted for axial motion in the direction of the axis of revolution of the annular toroidally shaped member. Passage of electrical current through the coil causes axial motion (reciprocal) of the separate annular curved segment. This motion is coupled to a hydraulic pump piston in a preferred embodiment.