A study on the plasma characteristics of inductively coupled electrode-less lamp

In this study the relationship between the electrode-less lamp\´s characteristics and the operating frequency for the ball shape electrode-less lamp like "QL" is investigated. 13.56 MHz and 135 kHz were used as the operating frequencies. The electrode-less lamp\´s characteristics include the starting characteristic, the plasma characteristics like the electron temperature or density, and the efficiency regarding UV radiation. The following results are found form this study: (1) The lamp driven at 13.56 MHz is ignited by H-discharge, while one driven at 135 kHz is ignited by E-discharge, and then changes into H-discharge. (2) The efficiency regarding UV radiation at 13.56 MHz was 7% higher than at 135 kHz. (3) The point of the peak of the electron density shifts from near the cavity to near the outer bulb when the operating frequency changes from 135 kHz to 13.56 MHz. (4) The electron temperature increases with coming closer to the cavity at 135 kHz operation, while it decreases at 13.56 MHz operation.