Ultrashort-Pulse Reflectometry in the Gamma 10 Device

An electron density profile is observed by using an ultrashort-pulse reflectometry in the central cell of the GAMMA 10 device. The pulse having 65 ps FWHM is launched into the plasma in the O-mode and reflected at the cut off layer. The frequency range of the receiving system is 6 to 11 GHz. Time of flight of the received signal is measured via a time to amplitude converter and processed by a computer. Here, electron density profile lower than 1.5 × 10¹⁸ m⁻³ is reconstructed within one-shot data. The time variation of the electron density profile is acquired. Reflected wave has information of fluctuation, simultaneously. Frequency spectrum of the fluctuation is also observed.