F. J. Raab

LIGO: The Laser Interferometer Gravitational-Wave Observatory

The goal of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Project is to detect and study astrophysical gravitational waves and use data from them for research in physics and astronomy. LIGO will support studies concerning the nature and nonlinear dynamics of gravity, the structures of black holes, and the equation of state of nuclear matter. It will also measure the masses, birth rates, collisions, and distributions of black holes and neutron stars in the universe and probe the cores of supernovae and the very early universe. The technology for LIGO has been developed during the past 20 years. Construction will begin in 1992, and under the present schedule, LIGOs gravitational-wave searches will begin in 1998.

IMPROVED SENSITIVITY IN A GRAVITATIONAL WAVE INTERFEROMETER AND IMPLICATIONS FOR LIGO

Sensitivity enhancements in the laser interferometer gravitational wave observatory (LIGO) projects 40 m interferometer have been achieved through two major instrumental improvements. Improved vibration isolation has reduced the noise due to ground motion. New test masses with less mechanical dissipation were installed to lower the thermal noise associated with mirror vibrations. The minimum interferometer noise (square root of the spectral density of apparent differential displacement) reached 3 x 10^(-19) m/Hz^(1/2) near 450 Hz.

Demonstration of a power-recycled Michelson interferometer with Fabry–Perot arms by frontal modulation

Large-scale gravitational-wave detectors currently under construction such as the LIGO detectors use multiplemirror resonant optical systems containing several surfaces at which the relative phase of interfering light beams must be controlled. We describe a tabletop experiment that demonstrates a scheme for extracting signals in such an interferometer corresponding to deviations from perfect interference.

Thermal noise in the test mass suspensions of a laser interferometer gravitational-wave detector prototype

Abstract The thermal noise of the test mass suspensions of a prototype gravitational-wave interferometer was calculated and found to be in agreement with the measured noise near the resonant frequencies of the suspensions. The damping mechanism of the suspension modes was characterized and found to be nearly independent of frequency.

Laser interferometer gravitational-wave observatory

The Laser Interferometer Gravitational-Wave Observatory (LIGO) will observe cosmic gravitational waves which induce small apparent displacements between suspended test masses. This talk reviews how developments in precision laser interferometry are addressing this goal.<<ETX>>

Suspension losses in the pendula of laser interferometer gravitational-wave detectors

Abstract We have experimentally tested models currently in use to estimate the mechanical losses and thermal noise of the test mass suspensions of laser interferometer gravitational-wave detectors. Observed losses are approximately independent of frequency from 1 Hz to 2 kHz, resulting in lower thermal noise estimates than with some previous models.

Observational Limit on Gravitational Waves from Binary Neutron Stars in the Galaxy

Using optimal matched filtering, we search 25 hours of data from the LIGO 40-m prototype laser interferometric gravitational-wave detector for gravitational-wave chirps emitted by coalescing binary systems within our Galaxy. This is the first test of this filtering technique on real interferometric data. An upper limit on the rate R of neutron star binary inspirals in our Galaxy is obtained: with 90% confidence, R<0.5h-1. Similar experiments with LIGO interferometers will provide constraints on the population of tight binary neutron star systems in the Universe.

The LSC glitch group: monitoring noise transients during the fifth LIGO science run

The LIGO Scientific Collaboration (LSC) glitch group is part of the LIGO detector characterization effort. It consists of data analysts and detector experts who, during and after science runs, collaborate for a better understanding of noise transients in the detectors. Goals of the glitch group during the fifth LIGO science run (S5) included (1) offline assessment of the detector data quality, with focus on noise transients, (2) veto recommendations for astrophysical analysis and (3) feedback to the commissioning team on anomalies seen in gravitational wave and auxiliary data channels. Other activities included the study of auto-correlation of triggers from burst searches, stationarity of the detector noise and veto studies. The group identified causes for several noise transients that triggered false alarms in the gravitational wave searches; the times of such transients were identified and vetoed from the data generating the LSC astrophysical results.

Shot noise in gravitational-wave detectors with Fabry-Perot arms.

Shot-noise-limited sensitivity is calculated for gravitational-wave interferometers with Fabry-Perot arms, similar to those being installed at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Italian-French Laser Interferometer Collaboration (VIRGO) facility. This calculation includes the effect of nonstationary shot noise that is due to phase modulation of the light. The resulting formula is experimentally verified by a test interferometer with suspended mirrors in the 40-m arms.

Measured limits to contamination of optical surfaces by elastomers in vacuum

We have monitored the reflectivity of mirrors that were exposed to a fluoroelastomer (3M-Fluorel 2176) and a room-temperature vulcanizing silicone rubber (RTV-615) in vacuum. The 95% confidence limit on the decrease of mirror reflectivities was less than 0.35 ppm/week for Fluorel and <0.29 ppm/week for RTV-615.