2,778 research outputs found
Energy Efficient Engine exhaust mixer model technology report addendum; phase 3 test program
The Phase 3 exhaust mixer test program was conducted to explore the trends established during previous Phases 1 and 2. Combinations of mixer design parameters were tested. Phase 3 testing showed that the best performance achievable within tailpipe length and diameter constraints is 2.55 percent better than an optimized separate flow base line. A reduced penetration design achieved about the same overall performance level at a substantially lower level of excess pressure loss but with a small reduction in mixing. To improve reliability of the data, the hot and cold flow thrust coefficient analysis used in Phases 1 and 2 was augmented by calculating percent mixing from traverse data. Relative change in percent mixing between configurations was determined from thrust and flow coefficient increments. The calculation procedure developed was found to be a useful tool in assessing mixer performance. Detailed flow field data were obtained to facilitate calibration of computer codes
A Single Atom as a Mirror of an Optical Cavity
By tightly focussing a laser field onto a single cold ion trapped in front of
a far-distant dielectric mirror, we could observe a quantum electrodynamic
effect whereby the ion behaves as the optical mirror of a Fabry-P\'erot cavity.
We show that the amplitude of the laser field is significantly altered due to a
modification of the electromagnetic mode structure around the atom in a novel
regime in which the laser intensity is already changed by the atom alone. e
propose a direct application of this system as a quantum memory for single
photons.Comment: 7 pages, 3 figures, to appear in Physical Review Letter
Centaur Propellant Thermal Conditioning Study
A wicking investigation revealed that passive thermal conditioning was feasible and provided considerable weight advantage over active systems using throttled vent fluid in a Centaur D-1s launch vehicle. Experimental wicking correlations were obtained using empirical revisions to the analytical flow model. Thermal subcoolers were evaluated parametrically as a function of tank pressure and NPSP. Results showed that the RL10 category I engine was the best candidate for boost pump replacement and the option showing the lowest weight penalty employed passively cooled acquisition devices, thermal subcoolers, dry ducts between burns and pumping of subcooler coolant back into the tank. A mixing correlation was identified for sizing the thermodynamic vent system mixer. Worst case mixing requirements were determined by surveying Centaur D-1T, D-1S, IUS, and space tug vehicles. Vent system sizing was based upon worst case requirements. Thermodynamic vent system/mixer weights were determined for each vehicle
QED with a spherical mirror
We investigate the Quantum-Electro-Dynamic properties of an atomic electron
close to the focus of a spherical mirror. We first show that the spontaneous
emission and excited state level shift of the atom can be fully suppressed with
mirror-atom distances of many wavelengths. A three-dimensional theory predicts
that the spectral density of vacuum fluctuations can indeed vanish within a
volume around the atom, with the use of a far distant mirror
covering only half of the atomic emission solid angle. The modification of
these QED atomic properties is also computed as a function of the mirror size
and large effects are found for only moderate numerical apertures. We also
evaluate the long distance ground state energy shift (Casimir-Polder shift) and
find that it scales as at the focus of a hemi-spherical mirror
of radius , as opposed to the well known scaling law for an
atom at a distance from an infinite plane mirror. Our results are relevant
for investigations of QED effects, and also free space coupling to single atoms
using high-numerical aperture lenses.Comment: 12 pages, 4 figure
Capillary acquisition devices for high-performance vehicles: Executive summary
Technology areas critical to the development of cryogenic capillary devices were studied. Passive cooling of capillary devices was investigated with an analytical and experimental study of wicking flow. Capillary device refilling with settled fluid was studied using an analytical and experimental program that resulted in successful correlation of a versatile computer program with test data. The program was used to predict Centaur D-1S LO2 and LH2 start basket refilling. Comparisons were made between the baseline Centaur D-1S propellant feed system and feed system alternatives including systems using capillary devices. The preferred concepts from the Centaur D-1S study were examined for APOTV and POTV vehicles for delivery and round trip transfer of payloads between LEO and GEO. Mission profiles were determined to provide propellant usage timelines and the payload partials were defined
Experimental proposal for accurate determination of the phase relaxation time and testing a formation of thermalized non-equilibrated matter in highly excited quantum many-body systems
We estimate how accurate the phase relaxation time of quantum many-body
systems can be determined from data on forward peaking of evaporating protons
from a compound nucleus. The angular range and accuracy of the data needed for
a reliable determination of the phase relaxation time are evaluated. The
general method is applied to analyze the inelastic scattering of 18 MeV protons
from Pt for which previously measured double differential cross sections for
two angles in the evaporating domain of the spectra show a strong forward
peaking. A new experiment for an improved determination of the phase relaxation
time is proposed. The experiment is also highly desirable for an accurate test
of a formation of thermalized non-equilibrated matter in quantum many-body
systems.Comment: 5 pages, 3 figure
Electromagnetically Induced Transparency from a Single Atom in Free Space
We report an absorption spectroscopy experiment and the observation of
electromagnetically induced transparency from a single trapped atom. We focus a
weak and narrowband Gaussian light beam onto an optically cooled Barium ion
using a high numerical aperture lens. Extinction of this beam is observed with
measured values of up to 1.3 %. We demonstrate electromagnetically induced
transparency of the ion by tuning a strong control beam over a two-photon
resonance in a three-level lambda-type system. The probe beam extinction is
inhibited by more than 75 % due to population trapping.Comment: 4 pages, 3 figure
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