Electrostatic self-plugging of a picket fence cusped magnetic field

Emissive Langmuir probes are used to map the plasma potential in the neighborhood of a picket fence cusped magnetic field. Positive potential ’’islands’’ are found in front of the picket fence conductors showing ion confinement by electrostatic self-plugging of the cusp leaks. This mechanism results in channels whose widths are the order of the hybrid cusp leak widths recently reported.