The Minimum-power Effect of a Magnetized Plasma

An experimental and theoretical analysis is performed of a fully ionized, magnetized, quasi-steady plasma being separated from a surrounding neutral gas blanket by partially ionized boundary regions: (i) For rotating as well as high-frequency heated plasmas there exists a sharply defined minimum heating power Pm and temperature T0m below which a steady fully ionized state cannot be maintained. At laboratory dimensions and ion densities of about 1021 m-3, these parameters become Pm 0.5 MW and T0m 2 × 104 K. This "minimum-P effect" is important both to the processes of creating and maintaining laboratory plasmas in fusion research and to the studies of certain cosmical plasmas. (ii) The theoretically predicted behaviour of the plasma is roughly in agreement with the experiments in the power range close to the minimum value.