12,013 research outputs found
Probing Dark Energy models with neutrons
There is a deep connection between cosmology -- the science of the infinitely
large --and particle physics -- the science of the infinitely small. This
connection is particularly manifest in neutron particle physics. Basic
properties of the neutron -- its Electric Dipole Moment and its lifetime -- are
intertwined with baryogenesis and nucleosynthesis in the early Universe. I will
cover this topic in the first part, that will also serve as an introduction (or
rather a quick recap) of neutron physics and Big Bang cosmology. Then, the rest
of the manuscript will be devoted to a new idea: using neutrons to probe models
of Dark Energy. In the second part, I will present the chameleon theory: a
light scalar field accounting for the late accelerated expansion of the
Universe, which interacts with matter in such a way that it does not mediate a
fifth force between macroscopic bodies. However, neutrons can alleviate the
chameleon mechanism and reveal the presence of the scalar field with properly
designed experiments. In the third part, I will describe a recent experiment
performed with a neutron interferometer at the Institut Laue Langevin that sets
already interesting constraints on the chameleon theory. Last, the chameleon
field can be probed by measuring the quantum states of neutrons bouncing over a
mirror. In the fourth part I will present the status and prospects of the
GRANIT experiment at the ILL
Anomalous radiative transitions
Anomalous transitions involving photons derived by many-body interaction of
the form, , in the standard model are studied. This
does not affect the equation of motion in the bulk, but makes wave functions
modified, and causes the unusual transition characterized by the
time-independent probability. In the transition probability at a time-interval
expressed generally in the form , now with . The diffractive term has the origin in the overlap of waves
of the initial and final states, and reveals the characteristics of waves. In
particular, the processes of the neutrino-photon interaction ordinarily
forbidden by Landau-Yang's theorem () manifests itself through the
boundary interaction. The new term leads to physical processes over a wide
energy range to have finite probabilities. New methods of detecting neutrinos
using laser are proposed that are based on this difractive term, which enhance
the detectability of neutrinos by many orders of magnitude.Comment: 47 pages, 5 figures, 1 table, typos correcte
Plasma Dynamics
Contains reports on six research projects.National Science Foundation (Grant ENG79-07047)U.S. Air Force - Office of Scientific Research (Grant AFOSR77-3143D)U.S. Air Force - Office of Scientific Research (Contract AFOSR82-0063)U.S. Department of Energy (Contract DE-ACO2-78-ET-51013)U.S. Department of Energy (Contract DE-AC02-78ET-53073.A002
Summary and recommendations on nuclear electric propulsion technology for the space exploration initiative
A project in Nuclear Electric Propulsion (NEP) technology is being established to develop the NEP technologies needed for advanced propulsion systems. A paced approach has been suggested which calls for progressive development of NEP component and subsystem level technologies. This approach will lead to major facility testing to achieve TRL-5 for megawatt NEP for SEI mission applications. This approach is designed to validate NEP power and propulsion technologies from kilowatt class to megawatt class ratings. Such a paced approach would have the benefit of achieving the development, testing, and flight of NEP systems in an evolutionary manner. This approach may also have the additional benefit of synergistic application with SEI extraterrestrial surface nuclear power applications
Industrial scale microwave applicator for high temperature alkaline hydrolysis of PET
A microwave design for an industrial scale applicator of a continuous microwave assisted depolymerization of polyethylene terephthalate (PET) has been developed. The cavity is designed for use in combination with an Archimedean screw pump to transport the reaction material, surrounded by a cylindrical pipe with a diameter of 250 mm and a length of 250 mm at the 2.45 GHz ISM band. The proposed design is modular and can be easily expanded for the heating of longer reactor tubes. Simulation results show that a homogeneous heating of the process material along the screw axis can be achieved by using a novel cavity design which is based on the TE1,0,x– rectangular waveguide cavity mode. The achieved design provides high energy efficiency with a reflected power of less than 10%. It is robust against changes in the permittivity of the reactants. The electromagnetic design is based on the dielectric properties of the solvolytic reaction mixture measured in the relevant temperature range. It is verified over the full range of the expected permittivities
Bright single-photon sources in bottom-up tailored nanowires
The ability to achieve near-unity light extraction efficiency is necessary
for a truly deterministic single photon source. The most promising method to
reach such high efficiencies is based on embedding single photon emitters in
tapered photonic waveguides defined by top-down etching techniques. However,
light extraction efficiencies in current top-down approaches are limited by
fabrication imperfections and etching induced defects. The efficiency is
further tempered by randomly positioned off-axis quantum emitters. Here, we
present perfectly positioned single quantum dots on the axis of a tailored
nanowire waveguide using bottom-up growth. In comparison to quantum dots in
nanowires without waveguide, we demonstrate a 24-fold enhancement in the single
photon flux, corresponding to a light extraction efficiency of 42 %. Such high
efficiencies in one-dimensional nanowires are promising to transfer quantum
information over large distances between remote stationary qubits using flying
qubits within the same nanowire p-n junction.Comment: 19 pages, 6 figure
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