88 research outputs found
Angular instability due to radiation pressure in the LIGO gravitational-wave detector
We observed the effect of radiation pressure on the angular sensing and control system of the Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometer’s core optics at LIGO Hanford Observatory. This is the first measurement of this effect in a complete gravitational-wave interferometer. Only one of the two angular modes survives with feedback control, because the other mode is suppressed when the control gain is sufficiently large. We developed a mathematical model to understand the physics of the system. This model matches well with the dynamics that we observe
Utilizing aLIGO glitch classifications to validate gravitational-wave candidates
Advanced LIGO data contains numerous noise transients, or 'glitches', that have been shown to reduce the sensitivity of matched filter searches for gravitational waves from compact binaries. These glitches increase the rate at which random coincidences occur, which reduces the significance of identified gravitational-wave events. The presence of these transients has precipitated extensive work to establish that observed gravitational wave events are astrophysical in nature. We discuss the response of the PyCBC search for gravitational waves from stellar mass binaries to various common glitches that were observed during advanced LIGO's first and second observing runs. We show how these transients can mimic waveforms from compact binary coalescences and quantify the likelihood that a given class of glitches will create a trigger in the search pipeline. We explore the specific waveform parameters that are most similar to different glitch classes and demonstrate how knowledge of these similarities can be used when evaluating the significance of gravitational-wave candidates
Effect of Optical Coating and Surface Treatments on Mechanical Loss in Fused Silica
We report on the mechanical loss in fused silica samples with various surface
treatments and compare them with samples having an optical coating. Mild
surface treatments such as washing in detergent or acetone were not found to
affect the mechanical loss of flame-drawn fused silica fibers stored in air.
However, mechanical contact (with steel calipers) significantly increased the
loss. The application of a high-reflective optical coating of the type used for
the LIGO test masses was found to greatly increase the mechanical loss of
commercially polished fused silica microscope slides. We discuss the
implications for the noise budget of interferometers.Comment: 7 pages, 2 figures. Accepted for publication in the Proceedings of
the Third Eduardo Amaldi Conference on Gravitational Waves, July 12-16, 1999.
Updated version contains a correction of Eq. 3 and an estimate for the loss
angle of a LIGO coating. (Neither of these revisions are included in the
version published in the conference proceedings.
Pendulum Mode Thermal Noise in Advanced Interferometers: A comparison of Fused Silica Fibers and Ribbons in the Presence of Surface Loss
The use of fused-silica ribbons as suspensions in gravitational wave
interferometers can result in significant improvements in pendulum mode thermal
noise. Surface loss sets a lower bound to the level of noise achievable, at
what level depends on the dissipation depth and other physical parameters. For
LIGO II, the high breaking strength of pristine fused silica filaments, the
correct choice of ribbon aspect ratio (to minimize thermoelastic damping), and
low dissipation depth combined with the other achievable parameters can reduce
the pendulum mode thermal noise in a ribbon suspension well below the radiation
pressure noise. Despite producing higher levels of pendulum mode thermal noise,
cylindrical fiber suspensions provide an acceptable alternative for LIGO II,
should unforeseen problems with ribbon suspensions arise.Comment: Submitted to Physics Letters A (Dec. 14, 1999). Resubmitted to
Physics Letters A (Apr. 3, 2000) after internal (LSC) review process. PACS -
04.80.Nn, 95.55.Ym, 05.40.C
A hierarchical method for vetoing noise transients in gravitational-wave detectors
Non-Gaussian noise transients in interferometric gravitational-wave detectors
increase the background in searches for short-duration and un-modelled signals.
We describe a method for vetoing noise transients by ranking the statistical
relationship between triggers in auxiliary channels that have negligible
sensitivity to gravitational waves and putative gravitational-wave triggers in
the detector output. The novelty of the algorithm lies in its hierarchical
approach, which leads to a minimal set of veto conditions with high performance
and low deadtime. After a given channel has been selected it is used to veto
triggers from the detector output, then the algorithm selects a new channel
that performs well on the remaining triggers and the process is repeated. This
method has been demonstrated to reduce the background in searches for transient
gravitational waves by the LIGO and Virgo collaborations.Comment: 13 page
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