ABSTRACT
INTRODUCTION Almost fifteen years have passed since the electrode-less lamp was put on the market. Some kinds of
the electrode-less lamps have been developed from a few companies for this fifteen years. The trends in the development of electrode-less lamps are to get the higher lumen output and to operate this lamp at lower frequency (compared with 13.56MHz). These two things are not conflicting, because for getting higher output it is necessary to increase the input power. As the result, the circuit efficiency should be increased. It seems that the easy way to increase the circuit efficiency is to decrease the operating frequency. In this situation it is considered to be important to grasp how the plasma performance depends on the operating frequency, and the research for this purpose has already held by Prof.Watanabe [1]. However, the research regarding the electron temperature and so on for this purpose has not reported yet.
