An experimental investigation of heating mechanisms, mode transition and instabilities in a radio frequency inductively coupled plasma
Crowley, Brendan J (2000) An experimental investigation of heating mechanisms, mode transition and instabilities in a radio frequency inductively coupled plasma. PhD thesis, Dublin City University.
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Radio frequency (RF) inductively coupled plasma (ICP) have been known and studied for over a century In recent years, due to the vast array of potential applications of plasma technology, research in the area has become more prolific. This thesis presents the results of a detailed experimental investigation that uses electrical diagnostics (Langmuir and magnetic field (5 ) probes etc ) on a particular type of inductively coupled plasma source (re-entrant cavity). The investigation focuses on three aspects of the ICP Firstly the heating mechanisms that sustain the plasma are characterized. It is found that the RF electric field and current density distributions determined from B probe measurements indicate a strong anomalous skin effect. This is exemplified by non-monotomc decay of the
electromagnetic fields, phase reversal and bifurcation, as well as negative power absorption regions. These features are interpreted m terms of spatial dispersion of the conductivity due to the electron thermal motion at low pressure. Secondly the E-H mode transition is comprehensively investigated using various steady state and time resolved diagnostics, the results show that hysteresis with respect to the transition current is accounted for by variation in the plasma production efficiency due to changes in the electron energy distribution function (EEDF) and the presence of metastable atoms Finally, a specific type of instability observed in low pressure ICPs is investigated experimentally and the results are found to agree on many points with a proposed model describing the instability.
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