Toroidal Fusion Plasma with Powerful Negative Bias

Abstract

Imposition of a powerful electrostatic bias allows a dense uniform-pressure plasma to be held in a static equilibrium in a toroidal closed-magnetic-line system. A small wall current of 3.5-MeV d-t alpha particles easily maintains the 6-MV/cm electric field necessary for controlled thermonuclear reaction conditions. As ions can be confined in an enormously deep energy well, the system lends itself also to production of highly stripped heavy nuclei.Since inception around 1952 the main thrust of controlled-nuclear-fusion research has been toward the confinement of neutral plasmas by strong static magnetic fields. In the present Letter it is pointed out that the imposition of a large electrostatic bias introduces a new degree of freedom into the design of plasma equilibria and allows several interesting objectives to be immediately attained. In particular, a dense, static, uniform-pressure plasma can be confined in a pure-toroidal closed-line magnetic field with toroidal electrostatic potential surfaces. In the proposed controlled thermonuclear reaction (CTR) device the ions are held in an energy well of enormous depth and the necessary bias is spontaneously maintained by a small wall current of 3.5-MeV d-t alpha particles. The stability of the electron-plasma heavy-ion plasma accelerator (HIPAC) system, analyzed and documented by Daugherty et al., 1 lends considerable encouragement that the proposed configuration may also be well behaved.We start the analysis of the toroidal equilibrium state by examining the equations for single-particle motion. In cylindrical coordinates (r, 0 ,z), symmetry in the azimuthal (9) direction provides that the angular momentum p e is a constant of the motion. With static fields the particle energy is also a constant and we make use of the approximate invariance of the magnetic moment ii. The particle energy H can then be writtenwhere q is the particle charge. The motion of the particle guiding center is restricted to the surface H-const; the guiding-center drift velocity along this surface is given to lowest order in Larmor radius byWe have chosen 6 = 0J3(r). The second term in-troduces 2 the effect of centrifugal force due to curved drift orbits. We now consider a region of space filled with density n(r) of particles of the same /i and J. The conservation law dn/dt+ V• (nv D ) =0 has an exact time-independent solution 3 [we make use of vx(g/r) = 0], n(n,J,r) = (B/r)[l + Cl~1(e*VXv D )]f(H),with Q = qB/mc. Inasmuch as the guiding center current differs from the perpendicular particle current only by the divergence-free magnetization current density VXM ? the guiding-center density in (3) is also the particle density to this order of approximation, Self-consistency of the low-/3 static equilibrium comes from the solution of the Poisson equation vV = -4?re £ £w/(M,«7,r)-^e(jU,J,r),in which the density terms are to be evaluated using the previous three equations.To avoid the undesirable buildup of electrostatic potentials large compared with kT/e in the interior of the proposed CTR plasma...

Efficiency of wave-driven rigid body rotation toroidal confinement

“…( 1). This is the principle of toroidal magnetoelectric confinement 2,6 . However, because of the difficulty to generate and control a radial electric field inside a hot plasma, electric rotation schemes have been far less explored than magnetic rotational transforms which underlie the basic field configurations of tokamak and stellarators.…”

“…The electric rotation schemes previously considered envisioned rotational transform only near the plasma periphery. Four decades ago, T. H. Stix identified 6 , described and analyzed 7,8 a toroidal trap based on a purely toroidal magnetic field supplemented by a radial electric field localized near the edge of the plasma and sustained by a preferential loss of fast ions. The orbit in such a trap comprises a vertical drift v D near the center of the discharge, closed by an electric E/B 0 rotation at the edge.…”

Nonlinear ohmic dissipation in axisymmetric DC and RF driven rotating plasmas

“…At a radius r, the power needed to sustain the RF driven G-J charge separation against collisional relaxation is locally given by the balance w i = e r dr/dt between Eqs. (35) and (51)…”

Flowing electron plasmas as modified current source

“…There has been considerable interest both experimentally and theoretically in toroidal nonneutral plasmas, which are relevant to heavy ion accelerators [1], sources of highly stripped heavy ions [2], and thermonuclear fusion reactors [3]. These concepts are based totally on the electrostatic confinement of ions in a deep potential cavity.…”