94,851 research outputs found
Comprehensive experimental analysis of nonlinear dynamics in an optically-injected semiconductor laser
We present the first comprehensive experimental study, to our knowledge, of the routes between nonlinear dynamics induced in a semiconductor laser under external optical injection based on an analysis of time-averaged measurements of the optical and RF spectra and phasors of real-time series of the laser output. The different means of analysis are compared for several types of routes and the benefits of each are discussed in terms of the identification and mapping of the nonlinear dynamics. Finally, the results are presented in a novel audio/video format that describes the evolution of the dynamics with the injection parameters. © 2011 Author(s)
The ArgoNeuT Detector in the NuMI Low-Energy beam line at Fermilab
The ArgoNeuT liquid argon time projection chamber has collected thousands of
neutrino and antineutrino events during an extended run period in the NuMI
beam-line at Fermilab. This paper focuses on the main aspects of the detector
layout and related technical features, including the cryogenic equipment, time
projection chamber, read-out electronics, and off-line data treatment. The
detector commissioning phase, physics run, and first neutrino event displays
are also reported. The characterization of the main working parameters of the
detector during data-taking, the ionization electron drift velocity and
lifetime in liquid argon, as obtained from through-going muon data complete the
present report.Comment: 43 pages, 27 figures, 5 tables - update referenc
Observation of thermally-induced magnetic relaxation in a magnetite grain using off-axis electron holography
A synthetic basalt comprising magnetic Fe3O4 grains (~ 50 nm to ~ 500 nm in diameter) is
investigated using a range of complementary nano-characterisation techniques. Off-axis electron
holography combined with in situ heating allowed for the visualisation of the thermally-induced
magnetic relaxation of an Fe3O4 grain (~ 300 nm) from an irregular domain state into a vortex state at
550˚C, just below its Curie temperature, with the magnetic intensity of the vortex increasing on cooling
Atmosphere-Ionosphere Response to the M9 Tohoku Earthquake Revealed by Joined Satellite and Ground Observations. Preliminary results
The recent M9 Tohoku Japan earthquake of March 11, 2011 was the largest
recorded earthquake ever to hit this nation. We retrospectively analyzed the
temporal and spatial variations of four different physical parameters -
outgoing long wave radiation (OLR), GPS/TEC, Low-Earth orbit tomography and
critical frequency foF2. These changes characterize the state of the atmosphere
and ionosphere several days before the onset of this earthquake. Our first
results show that on March 8th a rapid increase of emitted infrared radiation
was observed from the satellite data and an anomaly developed near the
epicenter. The GPS/TEC data indicate an increase and variation in electron
density reaching a maximum value on March 8. Starting on this day in the lower
ionospheric there was also confirmed an abnormal TEC variation over the
epicenter. From March 3-11 a large increase in electron concentration was
recorded at all four Japanese ground based ionosondes, which return to normal
after the main earthquake. We found a positive correlation between the
atmospheric and ionospheric anomalies and the Tohoku earthquake. This study may
lead to a better understanding of the response of the atmosphere /ionosphere to
the Great Tohoku earthquakeComment: Preliminary results reported at EGU 2011 in Vienna, Austri
Identification and tunable optical coherent control of transition-metal spins in silicon carbide
Color centers in wide-bandgap semiconductors are attractive systems for
quantum technologies since they can combine long-coherent electronic spin and
bright optical properties. Several suitable centers have been identified, most
famously the nitrogen-vacancy defect in diamond. However, integration in
communication technology is hindered by the fact that their optical transitions
lie outside telecom wavelength bands. Several transition-metal impurities in
silicon carbide do emit at and near telecom wavelengths, but knowledge about
their spin and optical properties is incomplete. We present all-optical
identification and coherent control of molybdenum-impurity spins in silicon
carbide with transitions at near-infrared wavelengths. Our results identify
spin for both the electronic ground and excited state, with highly
anisotropic spin properties that we apply for implementing optical control of
ground-state spin coherence. Our results show optical lifetimes of 60 ns
and inhomogeneous spin dephasing times of 0.3 s, establishing
relevance for quantum spin-photon interfacing.Comment: Updated version with minor correction, full Supplementary Information
include
Geo-neutrinos
We review a new interdisciplinary field between Geology and Physics: the
study of the Earth's geo-neutrino flux. We describe competing models for the
composition of the Earth, present geological insights into the make up of the
continental and oceanic crust, those parts of the Earth that concentrate Th and
U, the heat producing elements, and provide details of the regional settings in
the continents and oceans where operating and planned detectors are sited.
Details are presented for the only two operating detectors that are capable of
measuring the Earth's geo-neutrinos flux: Borexino and KamLAND; results
achieved to date are presented, along with their impacts on geophysical and
geochemical models of the Earth. Finally, future planned experiments are
highlighted
Noise Characterization and Filtering in the MicroBooNE Liquid Argon TPC
The low-noise operation of readout electronics in a liquid argon time
projection chamber (LArTPC) is critical to properly extract the distribution of
ionization charge deposited on the wire planes of the TPC, especially for the
induction planes. This paper describes the characteristics and mitigation of
the observed noise in the MicroBooNE detector. The MicroBooNE's single-phase
LArTPC comprises two induction planes and one collection sense wire plane with
a total of 8256 wires. Current induced on each TPC wire is amplified and shaped
by custom low-power, low-noise ASICs immersed in the liquid argon. The
digitization of the signal waveform occurs outside the cryostat. Using data
from the first year of MicroBooNE operations, several excess noise sources in
the TPC were identified and mitigated. The residual equivalent noise charge
(ENC) after noise filtering varies with wire length and is found to be below
400 electrons for the longest wires (4.7 m). The response is consistent with
the cold electronics design expectations and is found to be stable with time
and uniform over the functioning channels. This noise level is significantly
lower than previous experiments utilizing warm front-end electronics.Comment: 36 pages, 20 figure
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