Probing the Plasma Sheath by the Continuous Mass Loss of Microparticles

A novel approach of using microparticles as probes for the sheath structure of radio-frequency discharges is presented. Starting with a heavy (large) particle confined deep in the plasma sheath, the ambient plasma causes a continuous mass loss, which increases the levitation height of the particle. It is shown that this process can be precisely monitored with the phase-resolved resonance method, which allows probing the force balance of the particle with high spatial resolution. The resulting force profile is in reasonable agreement with recent sheath models.