1,985 research outputs found
The Advanced LIGO Photon Calibrators
The two interferometers of the Laser Interferometry Gravitaional-wave
Observatory (LIGO) recently detected gravitational waves from the mergers of
binary black hole systems. Accurate calibration of the output of these
detectors was crucial for the observation of these events, and the extraction
of parameters of the sources. The principal tools used to calibrate the
responses of the second-generation (Advanced) LIGO detectors to gravitational
waves are systems based on radiation pressure and referred to as Photon
Calibrators. These systems, which were completely redesigned for Advanced LIGO,
include several significant upgrades that enable them to meet the calibration
requirements of second-generation gravitational wave detectors in the new era
of gravitational-wave astronomy. We report on the design, implementation, and
operation of these Advanced LIGO Photon Calibrators that are currently
providing fiducial displacements on the order of
m/ with accuracy and precision of better than 1 %.Comment: 14 pages, 19 figure
Frequency-modulated continuous-wave LiDAR compressive depth-mapping
We present an inexpensive architecture for converting a frequency-modulated
continuous-wave LiDAR system into a compressive-sensing based depth-mapping
camera. Instead of raster scanning to obtain depth-maps, compressive sensing is
used to significantly reduce the number of measurements. Ideally, our approach
requires two difference detectors. % but can operate with only one at the cost
of doubling the number of measurments. Due to the large flux entering the
detectors, the signal amplification from heterodyne detection, and the effects
of background subtraction from compressive sensing, the system can obtain
higher signal-to-noise ratios over detector-array based schemes while scanning
a scene faster than is possible through raster-scanning. %Moreover, we show how
a single total-variation minimization and two fast least-squares minimizations,
instead of a single complex nonlinear minimization, can efficiently recover
high-resolution depth-maps with minimal computational overhead. Moreover, by
efficiently storing only data points from measurements of an
pixel scene, we can easily extract depths by solving only two linear equations
with efficient convex-optimization methods
H2B: Heartbeat-based Secret Key Generation Using Piezo Vibration Sensors
We present Heartbeats-2-Bits (H2B), which is a system for securely pairing
wearable devices by generating a shared secret key from the skin vibrations
caused by heartbeat. This work is motivated by potential power saving
opportunity arising from the fact that heartbeat intervals can be detected
energy-efficiently using inexpensive and power-efficient piezo sensors, which
obviates the need to employ complex heartbeat monitors such as
Electrocardiogram or Photoplethysmogram. Indeed, our experiments show that
piezo sensors can measure heartbeat intervals on many different body locations
including chest, wrist, waist, neck and ankle. Unfortunately, we also discover
that the heartbeat interval signal captured by piezo vibration sensors has low
Signal-to-Noise Ratio (SNR) because they are not designed as precision
heartbeat monitors, which becomes the key challenge for H2B. To overcome this
problem, we first apply a quantile function-based quantization method to fully
extract the useful entropy from the noisy piezo measurements. We then propose a
novel Compressive Sensing-based reconciliation method to correct the high bit
mismatch rates between the two independently generated keys caused by low SNR.
We prototype H2B using off-the-shelf piezo sensors and evaluate its performance
on a dataset collected from different body positions of 23 participants. Our
results show that H2B has an overwhelming pairing success rate of 95.6%. We
also analyze and demonstrate H2B's robustness against three types of attacks.
Finally, our power measurements show that H2B is very power-efficient
The Advanced LIGO photon calibrators
The two interferometers of the Laser Interferometry Gravitational-wave Observatory (LIGO) recently detected gravitational waves from the mergers of binary black hole systems. Accurate calibration of the output of these detectors was crucial for the observation of these events and the extraction of parameters of the sources. The principal tools used to calibrate the responses of the second-generation (Advanced) LIGO detectors to gravitational waves are systems based on radiation pressure and referred to as photon calibrators. These systems, which were completely redesigned for Advanced LIGO, include several significant upgrades that enable them to meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. We report on the design, implementation, and operation of these Advanced LIGO photon calibrators that are currently providing fiducial displacements on the order of 10-18m/Hz with accuracy and precision of better than 1%
Rapid and Accurate C-V Measurements
We report a new technique for the rapid measurement of full capacitance-voltage (C-V) characteristic curves. The displacement current from a 100-MHz applied sine wave, which swings from accumulation to strong inversion, is digitized directly using an oscilloscope from the MOS capacitor under test. A C-V curve can be constructed directly from this data but is severely distorted due to nonideal behavior of real measurement systems. The key advance of this paper is to extract the system response function using the same measurement setup and a known MOS capacitor. The system response correction to the measured C-V curve of the unknown MOS capacitor can then be done by simple deconvolution. No deskewing and/or leakage current correction is necessary, making it a very simple and quick measurement. Excellent agreement between the new fast C-V method and C-V measured conventionally by an LCR meter is achieved. The total time required for measurement and analysis is approximately 2 s, which is limited by our equipment
Towards a quantum representation of the ampere using single electron pumps
Electron pumps generate a macroscopic electric current by controlled
manipulation of single electrons. Despite intensive research towards a quantum
current standard over the last 25 years, making a fast and accurate quantised
electron pump has proved extremely difficult. Here we demonstrate that the
accuracy of a semiconductor quantum dot pump can be dramatically improved by
using specially designed gate drive waveforms. Our pump can generate a current
of up to 150 pA, corresponding to almost a billion electrons per second, with
an experimentally demonstrated current accuracy better than 1.2 parts per
million (ppm) and strong evidence, based on fitting data to a model, that the
true accuracy is approaching 0.01 ppm. This type of pump is a promising
candidate for further development as a realisation of the SI base unit ampere,
following a re-definition of the ampere in terms of a fixed value of the
elementary charge.Comment: 8 pages, 7 figure
Direct calibration of a true-rms ac voltmeter against a He-free pulsed Josephson standard
Starting from 2019 a new central role is played by quantum standards, owing to the redefined SI, where electrical units are directly linked to the fundamental constants e (elementary charge) and h (Planck constant). Thus, metrologists are nowadays trying to extend the astonishing accuracy attainable in dc measurements to ac and beyond, moving towards calibrations aiming quantum ac voltage generation. Programmable Josephson Voltage Standards are nowadays capable of fulfilling primary metrology requirements only for stepwise-approximated voltage signals up to few hundreds Hz. Pulsed Josephson standards are instead capable of generating arbitrary waveforms at higher frequencies, so are generally called Josephson Arbitrary Waveform Standards (JAWS). Despite of the lower attainable voltage, JAWS are very promising and are the subject of intense research activity. In particular, the capability of generating high spectral purity signals allows high accuracy measurements especially at the low voltage levels (<100 mV rms), which are challenging to be performed by the traditional ac-dc transfer difference using thermal converters. We report in the following about our setup for quantum-based calibrations of a true-rms ac voltmeter with low uncertainty, first results obtained and unsolved issues
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
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