Recently, a new relaxation theory of plasmas including the effects of flow has been constructed [1]. In this equilibrium state, two fluid (electron-ion) plasmas are represented by Double Beltrami fields and it provides a condition for the flow velocity v and β value of the plasmas to satisfy β + ( v / v_A )²/2 = const., where v_A is Alfven velocity. It follows from this equation ultra-high β (possibly β > 1) state will be realized due to the effects of the dynamic pressure of plasmas, when the plasma has fast flow comparable to v_A. In experimental search for the relaxed states of the flowing plasmas, normal-conducting (Proto-RT) or superconducting (Mini-RT) internal coil devices [2] have been constructed and fundamental researches are being carried out. When a radial electric field is generated in a poloidal magnetic field configuration of the internal conductor device, the expected E × B drift flow is induced in the toroidal direction of the plasmas.
In this study, we demonstrate the control of the radial electric field and toroidal flow of plasmas using a biased electrode and electron injection methods in Proto-RT. Plasmas are generated by 13.56MHz radio-frequency discharge and the typical electron density and electron temperature obtained were 10¹⁵m^-3 and 5eV. By applying a negative bias voltage on the ring electrode in Proto-RT, we have successfully controlled the potential profiles of plasmas in the internal conductor system and generated a radial electric field up to 3 kVm^-1. From emissive Langmuir probe and Mach probe measurements, the toroidal flow velocity of the plasma is estimated to be about 2×10⁴ms^-1, which is comparable to the ion sound speed, although some uncertainty remains due to the unmeasured ion temperature. Besides the use of the electrode for the formation of radial electric field and flow, non-neutralization of plasmas by an electron gun made of LaB₆ cathode is also currently planned. The experimental results of the potential control by these methods will be discussed.

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