1,609 research outputs found
CoMA: A high resolution Time-Of-Flight Secondary Ion Mass Spectrometer (TOF-SIMS) for in situ analysis of cometary matter
A lot of clues concerning the origin of the solar system can be found by sending an exploring spacecraft to a rendezvous with a comet. The space experiment CoMA, which will measure the elemental, isotopic, and molecular composition of cometary dust grains is described. It will be flown on NASA's Comet Rendezvous Asteroid Flyby (CRAF) mission
Machine-learning nonstationary noise out of gravitational-wave detectors
Signal extraction out of background noise is a common challenge in high-precision physics experiments, where the measurement output is often a continuous data stream. To improve the signal-to-noise ratio of the detection, witness sensors are often used to independently measure background noises and subtract them from the main signal. If the noise coupling is linear and stationary, optimal techniques already exist and are routinely implemented in many experiments. However, when the noise coupling is nonstationary, linear techniques often fail or are suboptimal. Inspired by the properties of the background noise in gravitational wave detectors, this work develops a novel algorithm to efficiently characterize and remove nonstationary noise couplings, provided there exist witnesses of the noise source and of the modulation. In this work, the algorithm is described in its most general formulation, and its efficiency is demonstrated with examples from the data of the Advanced LIGO gravitational-wave observatory, where we could obtain an improvement of the detector gravitational-wave reach without introducing any bias on the source parameter estimation
Development of life-test methodology for long-life mechanical components. Phase 1: Development of methodology
Improving LIGO calibration accuracy by tracking and compensating for slow temporal variations
Calibration of the second-generation LIGO interferometric gravitational-wave
detectors employs a method that uses injected periodic modulations to track and
compensate for slow temporal variations in the differential length response of
the instruments. These detectors utilize feedback control loops to maintain
resonance conditions by suppressing differential arm length variations. We
describe how the sensing and actuation functions of these servo loops are
parameterized and how the slow variations in these parameters are quantified
using the injected modulations. We report the results of applying this method
to the LIGO detectors and show that it significantly reduces systematic errors
in their calibrated outputs.Comment: 13 pages, 8 figures. This is an author-created, un-copyedited version
of an article published in Classical and Quantum Gravity. IOP Publishing Ltd
is not responsible for any errors or omissions in this version of the
manuscript or any version derived from i
Development of life-test methodology for long-life mechanical components. Phase 1: Development of methodology. Phase 2: Demonstration of methodology
Prediction for new magnetoelectric fluorides
We use symmetry considerations in order to predict new magnetoelectric
fluorides. In addition to these magnetoelectric properties, we discuss among
these fluorides the ones susceptible to present multiferroic properties. We
emphasize that several materials present ferromagnetic properties. This
ferromagnetism should enhance the interplay between magnetic and dielectric
properties in these materials.Comment: 12 pages, 4 figures, To appear in Journal of Physics: Condensed
Matte
Temperature dependence of charge transfer inefficiency in Chandra X-ray CCDs
Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the
focal plane instruments on the Chandra X-ray Observatory, suffered radiation
damage from exposure to soft protons during passages through the Earth's
radiation belts. The primary effect of the damage was to increase the charge
transfer inefficiency (CTI) of the eight front illuminated CCDs by more than
two orders of magnitude. The ACIS instrument team is continuing to study the
properties of the damage with an emphasis on developing techniques to mitigate
CTI and spectral resolution degradation. We present the initial temperature
dependence of ACIS CTI from -120 to -60 degrees Celsius and the current
temperature dependence after more than six years of continuing slow radiation
damage. We use the change of shape of the temperature dependence to speculate
on the nature of the damaging particles.Comment: 9 pages, 8 figures, to appear in Proc. SPIE vol 6276 "High Energy,
Optical, and Infrared Detectors for Astronomy II
Performance of the Charge Injection Capability of Suzaku XIS
A charge injection technique is applied to the X-ray CCD camera, XIS (X-ray
Imaging Spectrometer) onboard Suzaku. The charge transfer inefficiency (CTI) in
each CCD column (vertical transfer channel) is measured by the injection of
charge packets into a transfer channel and subsequent readout. This paper
reports the performances of the charge injection capability based on the ground
experiments using a radiation damaged device, and in-orbit measurements of the
XIS. The ground experiments show that charges are stably injected with the
dispersion of 91eV in FWHM in a specific column for the charges equivalent to
the X-ray energy of 5.1keV. This dispersion width is significantly smaller than
that of the X-ray events of 113eV (FWHM) at approximately the same energy. The
amount of charge loss during transfer in a specific column, which is measured
with the charge injection capability, is consistent with that measured with the
calibration source. These results indicate that the charge injection technique
can accurately measure column-dependent charge losses rather than the
calibration sources. The column-to-column CTI correction to the calibration
source spectra significantly reduces the line widths compared to those with a
column-averaged CTI correction (from 193eV to 173eV in FWHM on an average at
the time of one year after the launch). In addition, this method significantly
reduces the low energy tail in the line profile of the calibration source
spectrum.Comment: Paper contains 18 figures and 15 tables. Accepted for publication in
PAS
Machine-learning nonstationary noise out of gravitational-wave detectors
Signal extraction out of background noise is a common challenge in high-precision physics experiments, where the measurement output is often a continuous data stream. To improve the signal-to-noise ratio of the detection, witness sensors are often used to independently measure background noises and subtract them from the main signal. If the noise coupling is linear and stationary, optimal techniques already exist and are routinely implemented in many experiments. However, when the noise coupling is nonstationary, linear techniques often fail or are suboptimal. Inspired by the properties of the background noise in gravitational wave detectors, this work develops a novel algorithm to efficiently characterize and remove nonstationary noise couplings, provided there exist witnesses of the noise source and of the modulation. In this work, the algorithm is described in its most general formulation, and its efficiency is demonstrated with examples from the data of the Advanced LIGO gravitational-wave observatory, where we could obtain an improvement of the detector gravitational-wave reach without introducing any bias on the source parameter estimation
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