Collisional ionization rates for lithium and beryllium-like ions

Collisional ionization rates for lithium and beryllium-like ions deduced from time history of spectral lines emitted by these ions in hot plasma

Experimental rate coefficients for collisional excitation of lithium-like ions

Collisional excitation rates for lithium-like ions derived from diagnosed plasma produced in theta pinch device and line intensities emitted by these ion

Flowing gas, non-nuclear experiments on the gas core reactor

Flow tests were conducted on models of the gas core (cavity) reactor. Variations in cavity wall and injection configurations were aimed at establishing flow patterns that give a maximum of the nuclear criticality eigenvalue. Correlation with the nuclear effect was made using multigroup diffusion theory normalized by previous benchmark critical experiments. Air was used to simulate the hydrogen propellant in the flow tests, and smoked air, argon, or freon to simulate the central nuclear fuel gas. All tests were run in the down-firing direction so that gravitational effects simulated the acceleration effect of a rocket. Results show that acceptable flow patterns with high volume fraction for the simulated nuclear fuel gas and high flow rate ratios of propellant to fuel can be obtained. Using a point injector for the fuel, good flow patterns are obtained by directing the outer gas at high velocity along the cavity wall, using louvered or oblique-angle-honeycomb injection schemes

Feasibility study of full-reactor gas core demonstration test

Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved

Simplified models of electromagnetic and gravitational radiation damping

In previous work the authors analysed the global properties of an approximate model of radiation damping for charged particles. This work is put into context and related to the original motivation of understanding approximations used in the study of gravitational radiation damping. It is examined to what extent the results obtained previously depend on the particular model chosen. Comparisons are made with other models for gravitational and electromagnetic fields. The relation of the kinetic model for which theorems were proved to certain many-particle models with radiation damping is exhibited

Primordial magnetic fields and nonlinear electrodynamics

The creation of large scale magnetic fields is studied in an inflationary universe where electrodynamics is assumed to be nonlinear. After inflation ends electrodynamics becomes linear and thus the description of reheating and the subsequent radiation dominated stage are unaltered. The nonlinear regime of electrodynamics is described by lagrangians having a power law dependence on one of the invariants of the electromagnetic field. It is found that there is a range of parameters for which primordial magnetic fields of cosmologically interesting strengths can be created.Comment: 21 pages, 3 figure

Djelovanje snopa dušikovog lasera na površinu bakra

The ultraviolet and visible spectra of plasmas produced by N2-laser radiation focused onto a copper target in air and in vacuum have been recorded photographically. The nitrogen laser beam (α = 337 nm) had a maximum energy density of 1.1 J/cm2, the pulse duration was 6 ns, and the repetition rate 0.2 Hz. The measured electron temperature was 15000 K (±30%) in air and 13000 K (±50%) in vacuum and the electron densities were 6.5×10^17 cm^-3 (±60%) and 3.0×10^17 cm^-3 (±60%), respectively. The irradiated surface in air and in vacuum was studied employing a metallographic microscope. In vacuum, the droplets were created and expulsed at the crater edges. Their formation is explained by the hydrodynamical model. They were formed in a time interval which is about two times shorter than the duration of the laser pulse. In air, droplets were also formed. The weight loss from the Cu-crater in vacuum was about 0.3×10^-4 μmole/pulse, in air it was about three times less.Snopom iz N2-lasera, fokusiranim na površinu bakra u zraku i vakuumu, proizvodila se plazma. Ultraljubičast se i vidljiv spektar plazme snimao na film pomoću kvarcnog spektrografa. Impulsi iz lasera (λ = 337 nm) imali su najveću gustoću energije od 1.1 J/cm2, trajanje 6 ns i učestalost 0.2 Hz. Izmjerile su se elektronske temperature od 15000 K (±30%) u zraku i 13000 K (±50%) u vakuumu, a elektronske gustoće bile su 6.5 x 10^17 cm^-3 (±60%) odnosno 3.0 x 10^17 cm^-3 (±60%). Pomoću metalografskog mikroskopa proučavale su se površine ozračene u zraku i vakuumu. U vakuumu su oko rubova kratera nastajale kapljice u vremenu oko pola trajanja laserskog impulsa, i one su padale oko kratera. Njihovo se stvaranje objašnjava hidrodinamičkim modelom. I prilikom ozračivanja u zraku izbacivale su se kapljice. Izbačena masa iz kratera u bakru je u vakuumu iznosila oko 0.3×10^-4 μmola/impulsu, a oko trećinu toga u zraku

The Geoff Egan Memorial Lecture 2011. Artefacts, art and artifice: reconsidering iconographic sources for archaeological objects in early modern Europe

A first systematic analysis of historic domestic material culture depicted in contemporaneous Western painting and prints, c.1400-1800. Drawing on an extensive data set, the paper proposes to methodologies and hermeneutics for historical analysis and archaeological correspondence

The Vlasov limit and its fluctuations for a system of particles which interact by means of a wave field

In two recent publications [Commun. PDE, vol.22, p.307--335 (1997), Commun. Math. Phys., vol.203, p.1--19 (1999)], A. Komech, M. Kunze and H. Spohn studied the joint dynamics of a classical point particle and a wave type generalization of the Newtonian gravity potential, coupled in a regularized way. In the present paper the many-body dynamics of this model is studied. The Vlasov continuum limit is obtained in form equivalent to a weak law of large numbers. We also establish a central limit theorem for the fluctuations around this limit.Comment: 68 pages. Smaller corrections: two inequalities in sections 3 and two inequalities in section 4, and definition of a Banach space in appendix A1. Presentation of LLN and CLT in section 4.3 improved. Notation improve