Langmuir Probe Measurements in Low Frequency Inductively Coupled RF Plasmas

Experiments at the University of Maryland, Baltimore County’s Dusty Plasma Laboratory are being carried out with Langmuir probes used to measure electron temperature and radial density in inductively coupled plasmas with antennae frequencies ranging between 22 - 30 kHz, used to sustain dusty plasmas. The aim is to measure unmagnetized plasma density and temperature gradients, which we conjecture are amplified and responsible for ion momentum transfer to dust in the ∇P × B direction when a magnetic field is turned on. Our setup consists of a cylindrical glass chamber with external RF antennae, a glass shelf with ring electrodes to levitate and hold dust, and a Langmuir probe that is moveable in the axial and radial directions. Signals from the probe are routed into a digitizer with sample capability of up to 1 megasamples per second. The probe can be configured as a single or triple Langmuir probe that can measure argon plasma temperature and density changes as fast as 50 kHz, using 400 kHz probe sweeps.