Time average neutralized migma: A colliding beam/plasma hybrid physical state as aneutronic energy source — A review

Abstract

A D + beam of kinetic energy T i = 0.7 MeV was stored in a “simple mirror” magnetic field as self-colliding orbits or migma and neutralized by ambient, oscillating electrons whose bounce frequencies were externally controlled. Space charge density was exceeded by an order of magnitude without instabilities. Three nondestructive diagnostic methods allowed measurements of ion orbit distribution, ion storage times, ion energy distribution, nuclear reaction rate, and reaction product spectrum. Migma formed a disc 20 cm in diameter and 0.5 cm thick. Its ion density was sharply peaked in the center; the ion-to-electron temperature ratio was T i T e ∼ 10 3; ion-electron temperature equilibrium was never reached. The volume average and central D + density were n = 3.2 × 10 9 cm −3 and n c = 3 × 10 10 cm −3 respectively, compared to the space charge limit density n sc = 4 × 10 8 cm −3 . The energy confinement time was τ c = 20–30 s, limited by the change exchange reactions with the residual gas in the vacuum (5 × 10 −9 Torr). The ion energy loss rate was 1.4 keV/s. None of the instabilities that were observed in mirrors at several orders of magnitude lower density occurred. The proton energy spectrum for dd + d → T + p + 4 MeV shows that dd collided at an average crossing angle of 160°. Evidence for exponential density buildup has also been observed. Relative to Migma III results and measured in terms of the product of ion energy E, density n, and confinement time τ, device performance was improved by a factor of 500. Using the central fast ion density, we obtained the triple product: Tnτ ≅ 4 × 10 14 keV s cm −3, which is greater than that of the best fusion devices. The luminosity (collision rate per unit cross section) was ∼ 10 29 cm −2s −1, with o.7 A ion current through the migma center. The stabilizing features of migma are: (1) large Larmor radius; (2) small canonical angular momentum; (3) short axial length z (disc shape); (4) nonadiabatic motions in r and z; (5) precession and enegy spread; (6) ambipolar potential; (7) radial density gradient;(8) large ion-to-electron temperature ratio; (9) metal walls in z; (10) suitability for external stabilization techniques (small volume, recurrent surfacing of ions); and particularly (11) diamagnetic well. Extrapolition of the results to reactor densities led to a D + 3He reactor “basic migma disc” 0.5 m in diameter and 0.25 m thick, suspended in a 10 T field, generating 1.5 MW(th). A 2-MW(e) power plant would consist of 3 such discs in a common volume. referred to as a triplet migmacell. Its specific power is projected to be 1 MW(e)/ton. A large power plant of any size would consist of a large number of migma discs in a common volume. The advantages f such modular systems are: (1) economy of mass production: capital cost per kW will be 25% that of fission and 10% that of DT fusion; (2) plants will be economical for all sizes above 10 kW(e); (3) minimal heat pollution, thanks to direct conversion of the changed ion kinetic energy into electricity; (4) no proliferative potential; and (5) large power-to-weight ratio due to absence of shielding. Anticipated physics problems in density increase are discussed.