Generalized quasiperiodic Rauzy tilings

We present a geometrical description of new canonical $d$-dimensional codimension one quasiperiodic tilings based on generalized Fibonacci sequences. These tilings are made up of rhombi in 2d and rhombohedra in 3d as the usual Penrose and icosahedral tilings. Thanks to a natural indexing of the sites according to their local environment, we easily write down, for any approximant, the sites coordinates, the connectivity matrix and we compute the structure factor.Comment: 11 pages, 3 EPS figures, final version with minor change

Antimatter-driven fusion propulsion scheme for solar system exploration

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76531/1/AIAA-23527-891.pd

Reaction physics and mission capabilities of the magnetically insulated inertial confinement fusion reactor

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76048/1/AIAA-25451-882.pd

Gasdynamic fusion propulsion system for space exploration

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76953/1/AIAA-23876-408.pd

Solution of the Fokker-Planck transport equation by matrix factorization

A matrix factorization method is used to solve the Fokker-Planck (Landau) charged particle transport equation. By treating all phase space variables as discrete in analogy to Sn neutronics, the collision term takes on a five-point difference form which is readily treatable by this method. In order to illustrate this technique, the energy deposited by fast ions in a geometrically spherical, Maxwellian background plasma is calculated. Although this technique can be generalized to other geometries, its essential elements are best illustrated in this simple context.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24295/1/0000561.pd

Beta enhancement by relativistic electron rings in bumpy tori

The maximum achievable beta (ratio of plasma pressure to magnetic pressure) value in a bumpy torus such as Elmo (EBT) is determined primarily by the stability of the system to the interchange modes. These modes have as their source of free energy the drifts of the hot electron component that arise from the curvature and gradients of the confining magnetic field. At low (compared to the ion gyro) frequencies the only modes that exist are the core plasma and hot electron interchange, but at frequencies near the ion cyclotron frequency, instabilities arising from coupling of the interchange and compressional Alfven wave also appear. In most, if not all previous treatments of these instabilities, the hot electrons were treated as non-relativistic. In this paper we re-examine these modes using a relativistic formulation for the hot electrons which we also treat as highly anisotropic by neglecting their parallel momenta relative to the perpendicular momenta and their rest mass energy. We find a significant enhancement in the ion beta value as a result of treating the ring electrons relativistically. For typical present day EBT parameters we find that the value of the ion beta increases by about 50% as a result of increasing the hot electron mean energy from about several keV to few MeV. At such an energy the microwave power for heating these electrons is also optimum since the drag on the background plasma also reaches its minimum value.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25266/1/0000709.pd

Multigroup calculations of low energy neutral transport in tokamak plasmas

Multigroup discrete ordinates methods avoid many of the approximations that have been used in previous neutral transport analyses. Of particular interest are the neutral profiles generated as an integral part of larger plasma system simulation codes. To determine the appropriateness of utilizing a particular multigroup code, ANISN, for this purpose, results are compared with the neutral transport module of the Duchs code. For a typical TFTR plasma, predicted neutral densities differ by a maximum factor of three on axis and outfluxes at the plasma boundary by 40%. This is found to be significant for a neutral transport module. Possible sources of the observed discrepancies are indicated from an analysis of the approximations used in the Duchs model. Recommendations are made concerning the future application of the multigroup method

Dense Antihydrogen: Its Production and Storage to Envision Antimatter Propulsion

We discuss the possibility that dense antihydrogen could provide a path towards a mechanism for a deep space propulsion system. We concentrate at first, as an example, on Bose-Einstein Condensate (BEC) antihydrogen. In a Bose-Einstein Condensate, matter (or antimatter) is in a coherent state analogous to photons in a laser beam, and individual atoms lose their independent identity. This allows many atoms to be stored in a small volume. In the context of recent advances in producing and controlling BECs, as well as in making antihydrogen, this could potentially provide a revolutionary path towards the efficient storage of large quantities of antimatter, perhaps eventually as a cluster or solid.Comment: 12 pages, 3 figure