Plasma Containment by r.f. and d.c. Field Combinations†

Abstract

An investigation has been made concerning the use of radio frequency fields for the containment of hot, dense plasmas, such as those needed for controlled thermonuclear fusion. Because high losses due to skin effect are associated to r.f. fields, they will be used at the lowest possible frequency, and only where they constitute a useful supplement to the cheaper d.e. fields. Such r.f. fields are to be useful for reducing the plasma leakage present in most d.e. confinement systems, and to prevent some of the instabilities inherent to d.e. systems. One particular combination of d.e. and r.f. fields has been analysed in detail. It consists of a homogeneous axial d.e. magnetic field (or a d.e. mirror field) containing a plasma column against radial diffusion; the ends of the column are ‘ sealed ’ by moans of r.f. fields. By using the proper polarization of the r.f. fields, it is shown that appreciable plasma pressures can be contained, using r.f. fields of frequencies as low as a few megacycles. By using r.f. powers of the order of a few kilowatts, it is expected to be feasible to contain plasmas of a density exceeding 10¹⁴ charges/cm³ at temperatures exceeding 10 ev.