Hysteresis and mode transitions in inductively coupled Ar–Hg plasma in the electrodeless induction lamp

Long Qi, Chen Yuming and Chen Dahua

Institute for Electric Light Sources, Fudan University, Shanghai 200433, China
E-mail: Longqi@fudan.edu.cn

Abstract. Hysteresis and mode transitions in inductively coupled Ar–Hg plasma in the electrodeless induction lamp are studied at different discharge frequencies and under different matching conditions. It is observed that transition currents change at different frequencies and hysteresis exists not only between the starting and minimum maintaining currents of the electromagnetic mode (H mode) discharge but also between the starting and minimum maintaining currents of the electrostatic mode (E mode) discharge. The illuminance and global electrical parameters in the mode transitions are recorded. It is shown that the E to H mode transition is accompanied by increased plasma resistance and decreased plasma reactance, which results in a higher efficiency in the H mode. Under the same output voltage of the radio frequency source, mode transition can also be triggered by changing the matching condition. The emission spectra recorded before and after the E to H mode transition provide experimental evidence for the theory that the change of the electron energy distribution function plays an important role in the hysteresis effect.

Print publication: Issue 15 (7 August 2006)
Received 10 May 2006, in final form 9 June 2006
Published 21 July 2006

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