344 research outputs found
Instrument manual for the retarding ion mass spectrometer on Dynamics Explorer-1
The retarding ion mass spectrometer (RIMS) for Dynamics Explorer-1 is an instrument designed to measure the details of the thermal plasma distribution. It combines the ion temperature determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram direction. This manual provides a functional description of the RIMS, the instrument calibration, and a description of the commands which can be stored in the instrument logic to control its operation
Predicting Scattering Scanning Near-field Optical Microscopy of Mass-produced Plasmonic Devices
Scattering scanning near-field optical microscopy enables optical imaging and
characterization of plasmonic devices with nanometer-scale resolution well
below the diffraction limit. This technique enables developers to probe and
understand the waveguide-coupled plasmonic antenna in as-fabricated
heat-assisted magnetic recording heads. In order validate and predict results
and to extract information from experimental measurements that is physically
comparable to simulations, a model was developed to translate the simulated
electric field into expected near-field measurements using physical parameters
specific to scattering scanning near-field optical microscopy physics. The
methods used in this paper prove that scattering scanning near-field optical
microscopy can be used to determine critical sub-diffraction-limited dimensions
of optical field confinement, which is a crucial metrology requirement for the
future of nano-optics, semiconductor photonic devices, and biological sensing
where the near-field character of light is fundamental to device operation.Comment: article: 18 pages, 5 figures; SI: 15 pages, 12 figure
The retarding ion mass spectrometer on dynamics Explorer-A
An instrument designed to measure the details of the thermal plasma distribution combines the ion temperature-determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram directions. The retarding ion mass spectrometer, its operational modes and calibration are described as well as the data reduction plan, and the anticipated results
Collection of indirect excitons in a diamond-shaped electrostatic trap
We report on the principle and realization of a new trap for excitons -- the
diamond electrostatic trap -- which uses a single electrode to create a
confining potential for excitons. We also create elevated diamond traps which
permit evaporative cooling of the exciton gas. We observe collection of
excitons towards the trap center with increasing exciton density. This effect
is due to screening of disorder in the trap by the excitons. As a result, the
diamond trap behaves as a smooth parabolic potential which realizes a cold and
dense exciton gas at the trap center.Comment: 4 Pages, 5 figure
Localization-Delocalization Transition of Indirect Excitons in Lateral Electrostatic Lattices
We study transport of indirect excitons in GaAs/AlGaAs coupled quantum wells
in linear lattices created by laterally modulated gate voltage. The
localization-delocalization transition (LDT) for transport across the lattice
was observed with reducing lattice amplitude or increasing exciton density. The
exciton interaction energy at the transition is close to the lattice amplitude.
These results are consistent with the model, which attributes the LDT to the
interaction-induced percolation of the exciton gas through the external
potential. We also discuss applications of the lattice potentials for
estimating the strength of disorder and exciton interaction.Comment: 4 pages, 4 figure
Comparison between three-dimensional linear and nonlinear tsunami generation models
The modeling of tsunami generation is an essential phase in understanding
tsunamis. For tsunamis generated by underwater earthquakes, it involves the
modeling of the sea bottom motion as well as the resulting motion of the water
above it. A comparison between various models for three-dimensional water
motion, ranging from linear theory to fully nonlinear theory, is performed. It
is found that for most events the linear theory is sufficient. However, in some
cases, more sophisticated theories are needed. Moreover, it is shown that the
passive approach in which the seafloor deformation is simply translated to the
ocean surface is not always equivalent to the active approach in which the
bottom motion is taken into account, even if the deformation is supposed to be
instantaneous.Comment: 39 pages, 16 figures; Accepted to Theoretical and Computational Fluid
Dynamics. Several references have been adde
Effect of spatial resolution on the estimates of the coherence length of excitons in quantum wells
We evaluate the effect of diffraction-limited resolution of the optical
system on the estimates of the coherence length of 2D excitons deduced from the
interferometric study of the exciton emission. The results are applied for
refining our earlier estimates of the coherence length of a cold gas of
indirect excitons in coupled quantum wells [S. Yang et al., Phys. Rev. Lett.
97, 187402(2006)]. We show that the apparent coherence length is well
approximated by the quadratic sum of the actual exciton coherence length and
the diffraction correction given by the conventional Abbe limit divided by
3.14. In practice, accounting for diffraction is necessary only when the
coherence length is smaller than about one wavelength. The earlier conclusions
regarding the strong enhancement of the exciton coherence length at low
temperatures remain intact.Comment: 6 pages, 5 figure
Modulational and Parametric Instabilities of the Discrete Nonlinear Schr\"odinger Equation
We examine the modulational and parametric instabilities arising in a
non-autonomous, discrete nonlinear Schr{\"o}dinger equation setting. The
principal motivation for our study stems from the dynamics of Bose-Einstein
condensates trapped in a deep optical lattice. We find that under periodic
variations of the heights of the interwell barriers (or equivalently of the
scattering length), additionally to the modulational instability, a window of
parametric instability becomes available to the system. We explore this
instability through multiple-scale analysis and identify it numerically. Its
principal dynamical characteristic is that, typically, it develops over much
larger times than the modulational instability, a feature that is qualitatively
justified by comparison of the corresponding instability growth rates
The generalized 3-edge-connectivity of lexicographic product graphs
The generalized -edge-connectivity of a graph is a
generalization of the concept of edge-connectivity. The lexicographic product
of two graphs and , denoted by , is an important graph
product. In this paper, we mainly study the generalized 3-edge-connectivity of
, and get upper and lower bounds of .
Moreover, all bounds are sharp.Comment: 14 page
Pattern formation in 2-frequency forced parametric waves
We present an experimental investigation of superlattice patterns generated
on the surface of a fluid via parametric forcing with 2 commensurate
frequencies. The spatio-temporal behavior of 4 qualitatively different types of
superlattice patterns is described in detail. These states are generated via a
number of different 3--wave resonant interactions. They occur either as
symmetry--breaking bifurcations of hexagonal patterns composed of a single
unstable mode or via nonlinear interactions between the two primary unstable
modes generated by the two forcing frequencies. A coherent picture of these
states together with the phase space in which they appear is presented. In
addition, we describe a number of new superlattice states generated by 4--wave
interactions that arise when symmetry constraints rule out 3--wave resonances.Comment: The paper contains 34 pages and 53 figures and provides an extensive
review of both the theoretical and experimental work peformed in this syste
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