Testing of an Electrostatic Dust Detector for Low-Temperature Plasma Environments

Dust detection and mitigation are key tasks to improve the performance of plasma processing chambers. In this work, we test the practical functionality of an electrostatic dust detector [1,2] for use in low-temperature plasma environments, using conductive dust of graphite and aluminum as well as dielectric dust of Al₂O₃. We operate an electrified grid which experiences a pulse of electric current when dust lands between the grid's traces. By estimating properties of the dust such as grain size and electrical resistance from peak current amplitude and decay time, we test a proposed circuit-element model of the dust detector. We conduct experiments with uncharged dust in an ambient (open-air) environment before charging dielectric dust in an RF argon plasma [3], testing it within a vacuum chamber to attempt to identify the charge the dust accumulates in the plasma. The experiments with conductive dust in ambient air reliably produce current pulses up to 10 mA upon hitting the grid, whereas the dielectric particles tested with and without plasma do not show any reproducible signals. Due to the dominant influence of the detection circuit's capacitance and resistance, the dust particle properties (e.g., size, material) may have a negligible effect on the measured pulsed current signal amplitude and decay time.



[1] A. Bader, C. H. Skinner, A. L. Roquemore, S. Langish; Development of an electrostatic dust detector for use in a tokamak reactor. Rev. Sci. Instrum. 1 February 2004; 75 (2): 370–375.

[2] C. H. Skinner, B. Rais, A. L. Roquemore, H. W. Kugel, R. Marsala, T. Provost; First real-time detection of surface dust in a tokamak. Rev. Sci. Instrum. 1 October 2010; 81 (10): 10E102.

[3] Y. Ussenov, M.N. Shneider, S. Yatom, Y. Raitses, APS Gaseous Electronics Conference, IT4.055, (023)