Plasma containment in cusp-shaped magnetic fields

Abstract

Advances in the subject of plasma containment in cusp-shaped magnetic fields over the past six or more years are reviewed. Particular emphasis is placed on the structure and thickness of the sheath separating a field-free plasma from a vacuum magnetic field. Recent experimental results suggest possibly that the thickness could be the geometric mean of the electron and ion Larmor radii, compared to earlier results in which the thickness measured was nearer the ion Larmor radius. The electric field in the sheath is important not only in determining its structure but also in problems associated with flow, end shorting, losses, and plasma rotation and stability. The present status of radio-frequency and electrostatic plugging of the ends is presented. Liner implosion to obtain extreme, and perhaps optimal, conditions for controlled fusion is a new aspect of this subject which deserves some attention. Hybrid schemes which employ cuspshaped magnetic fields as an essential part of their containment configuration include the linear picket fence, the spherical multipole magnetic trap, the stuffed cusp, the caulked stuffed cusp, the caulked cusp torus (CCT), the toroidal line cusp (or Tormac), and the containment of a flowing plasma in toroidal multiple cusps (the Polytron). These are reviewed, and their advantages and disadvantages for fusion are discussed.

Sudden Jumps, Hysteresis, and Negative Resistance in an Argon Plasma Discharge. II. Discharges in Magnetic Fields

“…This leak width varies inversely with B (see, e.g., HAINES [13]). In this case the effect of the magnetic field on plasma Confinement is analogous, in the field-free case, t o the role of neutral pressure on plasma production.…”

Magnetostatic penumbra models with field-free gaps

“…This configuration occurs whenever a field free plasma penetrates into a magnetic field, and is known in the controlled-fusion literature as a "cusp". Cuspy configurations like the "stellarator" and the "picket fence" play a role as alternatives to the Tokamak configuration, because of their inherent MHD-stability (e.g., Rose & Clark 1961;Artsymovich 1964;Haines 1977). Consider first the simple case B y = 0 and, without loss of generality, ignore the gas pressure inside the magnetic region.…”

Tearing Modes Growth Rate Amplification Due to Finite Current Relaxation

“…Beyond the above mentioned qualitative result, can we quantify the change of the growth rate due to a change on the perturbative wavelength? To answer this question, first we observe that the product ∆ a, in the general equation (35), is a function of the product ka [45][46][47][48][49]. Perhaps, the most illustrative example of this issue is provided by the so-called Harris model, which assumes the profile [50] …”