Thermonuclear Fusion Plasmas Research Articles

Calculation of spectator satellite lines of nickel-like gold ions in high density thermonuclear plasma

X-ray emissions and absorptions by highly charged ions play an important role in high density thermonuclear fusion plasma. Transition energies and oscillator strengths have been calculated for many combinations of the states of nickel-like gold ions with one or two spectator electrons. A relativistic atomic structure calculation has been carried out. Although the size of the calculation is quite large, a line by line analysis for such a system is well tractable.

Wave propagation in one-dimensional inhomogeneous random media with an application to lower hybrid waves in fusion plasmas

Wave propagation in a one-dimensional stratified medium, whose physical parameters are subject to random fluctuations, is considered. The complex-valued reflection coefficient obeys, as a function of the slab width L, a stochastic Riccati differential equation, associated with an initial-value problem. Using this fact, solving first the boundary-value problem satisfied by the field on [0,L] is avoided. The reflection coefficient can be computed numerically by a Monte-Carlo-type procedure by the generation of suitable sequences of random numbers aimed at constructing realizations of the stochastic processes that enter the refractive index. An application is made to the propagation of ‘‘lower hybrid waves’’ in thermonuclear (fusion) plasmas for realistic models of the deterministic density profile using available experimental data for the statistics of the random fluctuations. Several functional forms of the density profile are considered, and the relevant physical approximations are discussed. This work generalizes a previous analysis that did not include the inhomogeneous background density profile. Results show that the reflected power is a sensitive function of the form of the density profile.

High-power TE11 and TM11 circular polarizers in oversized waveguides at 70 GHz

Elliptical deformation of oversized, smooth-wall circular waveguides can produce choosable elliptical or circular polarization from a linearly polarized TE11 or TM11 mode used as intermediate linearly polarized modes in TEO1 to HE11 mode conversion sequences in electron cyclotron resonance heating (ECRH) of magnetically confined thermonuclear fusion plasmas with high-power gyrotrons. Mode coupling in elliptically distorted overmoded circular waveguides has been studied theoretically and experimentally in order to optimize TE11 (and TM11) polarizers (I.D.=27.79 mm) for the 1 MW/70 GHz long-pulse (3s) ECRH system on the Garching Stellarator W VII-AS. Coupling coefficients for ellipticity coupling of non-degenerate modes are given (coupled-mode differential equations formalism). The polarization converters essentially consist of smooth-wall circular waveguides which are gradually squeezed. A sine-squared function of the length coordinate is used to get an almost elliptical crosssection in the middle and circular cross sections at both ends. Arbitrary elliptical polarization states can be generated introducing an extremely low level (<<1%) of undesired spurious modes. Well defined differential phase characteristics have been achieved.

An effect of nuclear electric quadrupole moments in thermonuclear fusion plasmas

Consideration of the nuclear electric quadrupole terms in the expression for the fusion Coulomb barrier suggests that this electrostatic barrier may be substantially modified from that calculated under the usual plasma assumption that the nuclei are electric monopoles. This effect is a result of the nonspherical potential shape and the spatial quantization of the nuclear spins of the fully stripped ions in the presence of a magnetic field. For monopole-quadrupole fuel cycles like p-B-11, the fusion cross-section may be substantially increased at low energies if the protons are injected at a small angle relative to the confining magnetic field.

Very-high-density plasmas for thermonuclear fusion

It is shown that for plasma-confinement times inferior to the Bohm diffusion time, fusion reactors are conceivable only when densities above 1019 ions/cm3 are considered. Two classes of such reactors are examined: the non-selfdestructive and the selfdestructive devices. A review is given of experiments and of theories concerning both classes (the plasma focus, the axial flow-pinch, the inertial confinement, the laser and electron-beam produced plasmas and the plasmas produced by projectile-impact). Non-fusion applications are also discussed. Reactor and trigger criteria are derived in the appendices.