185,831 research outputs found
Spheromak Experiment Using Separate Guns For Formation And Sustainment
An experiment is described that incorporates the use of separate magnetized plasma guns for formation and sustainment of a spheromak. It is shown that energy coupling efficiency approaches unity if the gun and spheromak are of comparable size. A large gun should be able to operate at lower current and therefore lower voltage. In addition, it is expected that a gun matched to the size of the spheromak will cause less perturbation to the equilibrium. It is proposed to use a smaller gun for spheromak formation and a large, efficient gun for sustainment. The theoretical basis for the experiment is developed, and the details of the experiment are described. A prediction of the equilibrium magnetic flux surfaces using the EFIT code is presented
Dust outflows and inner gaps generated by massive planets in debris disks
Main sequence stars are commonly surrounded by debris disks, formed by cold
far-IR-emitting dust that is thought to be continuously replenished by a
reservoir of undetected dust-producing planetesimals. We have investigated the
orbital evolution of dust particles in debris disks harboring massive planets.
Small dust grains are blown out by radiation pressure, as is well known; in
addition, gravitational scattering by the giant planets also creates an outflow
of large grains. We describe the characteristics of this large-particle outflow
in different planetary architectures and for different particle sizes. In
addition, the ejection of particles is responsible for the clearing of dust
inside the orbit of the planet. We study the efficiency of particle ejection
and the resulting dust density contrast inside and outside the orbit of the
planet, as a function of the planet's mass and orbital elements and the
particle size. We discuss its implications for exo-planetary debris disks and
for the interpretation of in-situ dust detection experiments on space probes
traveling in the outer solar system.Comment: 32 pages (pre-print format), including 12 figures. Accepted to ApJ
(2005). Due to space constrains Fig. 3-6 are at very low resolutio
Compatibility analysis for the 1535-1660 MHz band, part 1 Final report, Jan. - Sep. 1969
Electromagnetic compatibility and radio frequency interference of aircraft radio antenna
The Casimir Effect
After a review of the standard calculation of the Casimir force between two
metallic plates at zero and non-zero temperatures, we present the study of
microscopic models to determine the large-distance asymptotic force in the
high-temperature regime. Casimir's conducting plates are modelized by plasmas
of interacting charges at temperature T. The charges are either classical, or
quantum-mechanical and coupled to a (classical) radiation field. In these
models, the force obtained is twice weaker than that arising from standard
treatments neglecting the microscopic charge fluctutations inside the bodies.
The enforcement of inert boundary conditions on the field in the usual
calculations turns out to be inadequate in this regime.
Other aspects of dispersion forces are also reviewed. The status of
(non-retarded) van der Waals-London forces in a dilute medium of non-zero
temperature and density is investigated. In a proper scaling regime called the
atomic limit (high dilution and low temperature), one is able to give the exact
large-distance atomic correlations up to exponentially small terms as T->0.
Retarded van der Waals forces and forces between dielectric bodies are also
reviewed.
Finally, the Casimir effect in critical phenomena is addressed by considering
the free Bose gas. It is shown that the grand-canonical potential of the gas in
a slab at the critical value of the chemical potential has finite size
corrections of the standard Casimir type. They can be attributed to the
existence of long-range order generated by gapless excitations in the phase
with broken continuous symmetry.Comment: Lecture notes prepared for the proceedings of the 1st Warsaw School
of Statistical Physics, Kazimierz, Poland, June 2005. To appear in Acta
Physica Polonica (2006). 52 pages, 0 figures. Available at
http://th-www.if.uj.edu.pl/acta/vol37/pdf/v37p2503.pd
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