Alternating current operation could be an alternative method for producing a steady state power output in tokamak fusion reactor with a small thermal energy storage system. In case of KAIST-TOKAMAK, AC disharge is used for wall-cleaning to achieve good plasma. However, there were not characteristics of AC plasma in KAIST-TOKAMAK. The main purpose of this study is to get database about AC discharge plasma and . A puzzle arising from this study is the finite plasma density observed during current reversal phase. This phenomenon is arised from the particle confinement effect by the finite magnetic flux surface due to finite local plasma current profile, and fast oscillation(22 kHz) of plasma current. To prove the existence of local plasma current indirectly, spatio-temporal electron density profile is measured.
Using rogowski loop, triple probe and Ha diagnostic, electron density profile, temperature, plasma current and other parameters is obtained. The more reliable results to the plasma current profile could be from the internal scanning magnetic probe and spectroscopic diagnostic system. Moreover, it need to get information about the process of the time-varying removing chemical gaebages in the vacuum vessel.
