Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres.
A method for measuring the time-averaged vertical electric field and its gradient in the plasma sheath using clusters with n = 2 or 3 floating microspheres of known mass is described. The particle charge q is found by determining the ratio of the breathing frequency to the center-of-mass frequency for horizontal (in-plane) oscillations. The electric field at the position of the particles is then calculated using the measured charge-to-mass ratio, and the electric-field gradient is determined from the vertical resonance frequency. The Debye length is also found. Experimental results are in agreement with a simple sheath model.
Sheridan
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Department of Physics & Astronomy, Ohio Northern University, Ada, Ohio 45810, USA. t-sheridan@onu.edu
Katschke
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Wells
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