Physical Sciences and Mathematics Commons^™

Identification And Reduction Of Scattered Light Noise In Ligo, Siddharth Soni

LSU Doctoral Dissertations

We ushered into a new era of gravitational wave astronomy in 2015 when Advanced LIGO gravitational wave detectors in Livingston, Louisiana and Hanford, Washington observed a gravitational wave signal from the merger of binary black holes. The first detected GW150914 was a part of first Observing run (O1) and since then there have been a total of 3 Observing runs. Advanced Virgo detector in Cascina, Italy joined the efforts in the third Observing run (O3) which spanned from April 1, 2019, to March 27, 2020. It was split into O3a and O3b with a month long break between them, during …

Measurements And Mitigation Of Scattered Light Noise In Ligo, Corey Daniel Austin

LSU Doctoral Dissertations

The Advanced LIGO (aLIGO) detectors use 1064 nm lasers to measure the tiny fluctuations in spacetime that occur when gravitational waves pass through the earth. LIGO makes use of advanced coating methods and materials to limit the amount of light that scatters from the main beam, but some amount of light does scatter. This stray light can interact with surfaces inside the interferometer that are not seismically isolated and then recombine with the main beam, introducing excess noise into the gravitational wave channel. This thesis reviews the methods for modeling scattered light with ray tracing software and analytical models, for …

Calibration Transients In Ligo Detectors, Thomas Daniel Abbott

LSU Doctoral Dissertations

This dissertation describes a novel method of analyzing fluctuations in the time-dependent calibration models of the LIGO interferometers to estimate their effect on strain reconstruction for gravitational-wave detections. The time-dependence of the calibration model of each detector is tracked with a set of parameters which are continuously measured while the interferometers are operating. These parameters track slow variations in the sensing function of the detectors as well as the actuators that hold the detectors in an operational state. The time-dependent parameter data during the second observation run (O2 [November 30, 2016 16:00 UTC to August 25, 2017 22:00:00 UTC]) and …

High Power And Optomechanics In Advanced Ligo Detectors, Terra Christine Hardwick

LSU Doctoral Dissertations

In September 2015, a new era of astronomy began with the first direct detection of grav- itational waves from a binary black hole coalescence. The event was captured by the Laser Interferometer Gravitational-wave Observatory, comprised of two long-baseline interferometers, one in Livingston, LA and one in Hanford, WA. At the time of the first detection, the interferometers were part way through an upgrade to an advanced configuration and were operating with a strain sensitivity of just better than 10⁻²³/Hz^1/2 around 100Hz. The full Advanced LIGO design calls for sensitivity of a few parts in 10⁻²⁴/Hz …

Broadband Measurement And Reduction Of Quantum Radiation Pressure Noise In The Audio Band, Jonathan Daniel Cripe

LSU Doctoral Dissertations

One hundred years after Albert Einstein predicted the existence of gravitational waves in his general theory of relativity, the Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first direct detection of gravitational waves. Since the first detection of gravitational waves from a binary black hole merger, LIGO has gone on to detect gravitational waves from multiple binary black hole mergers, and more recently from a binary neutron star merger in collaboration with telescopes around the world. The detection of gravitational waves has opened a new window to the universe and has launched the era of gravitational wave astronomy.

With the first …

The Effects Of Instrumental Noise On Searches For Generic Transient Gravitational Waves In Advanced Ligo, Marissa Walker

LSU Doctoral Dissertations

One hundred years after Albert Einstein predicted the existence of gravitational waves as a result of his theory of general relativity, the Laser Interferometer Gravitational-Wave Observatory (LIGO), made the first direct detection of a gravitational-wave signal from a binary black hole merger, GW150914. GW150914 was found not only by search methods specifically developed to find the distinctive waveform produced by coalescing binaries, but also by generic searches designed to find any arbitrary short-duration signal in the LIGO data. The impact of noise on the searches must be carefully investigated in order to reduce the search background and enable confident gravitational-wave …

Performance Characterization Of The Dual-Recycled Michelson Subsystem In Advanced Ligo, Anamaria Effler

LSU Doctoral Dissertations

General relativity predicts the existence of gravitational waves as ripples in spacetime propagating at the speed of light. They couple to matter weakly, which implies only cataclysmic cosmic events generating such waves can be detected. Binary neutron star coalescences are, for example, one of the most promising detectable source. Their weak coupling also implies that very sensitive instruments are needed to detect them, and the most sensitive so far have been laser interferometers with km-scale arms. The Laser Interferometric Gravitational wave Observatory (LIGO) is exactly such an instrument, and the most sensitive in the world to the date of this …

Searches For Gravitational Waves From Perturbed Black Holes In Data From Ligo Detectors, Sarah Elizabeth Caudill

LSU Doctoral Dissertations

Black hole perturbation theory predicts that a perturbed black hole will emit gravitational waves in a superposition of quasi-normal modes. Various astrophysical processes can produce such a black hole including the merger of two compact binary neutron stars or black holes. The final form of the waveform from such a system is known as a ringdown. We discuss the search through data from LIGO's fifth science run for ringdown gravitational waves from intermediate mass black holes using a matched filtering pipeline. We outline the improvements to the pipeline since LIGO's fourth science run including the creation of a fully automated …

Calibrating And Improving The Sensitivity Of The Ligo Detectors, Jeffrey S. Kissel

LSU Doctoral Dissertations

The Laser Interferometer Gravitational wave Observatory (LIGO) is network of three, power recycled Fabry-Perot Michelson interferometers built to detect gravitational waves from astrophysical sources at frequencies between 40 and 6000 Hz. For their fifth science run, from 2005 to 2007, the detectors observed at designed sensitivity, achieving equivalent strain amplitude noise of 3x10^−23 strain/rtHz at 100 Hz. To date, the observatory has not detected gravitational waves. However, even at such sensitivity, the expected detection rate for known astrophysical sources of gravitational waves is likely 0.02 yr^−1. The fundamental noise source of these ground-based detectors limiting the sensitivity below 40 Hz …

Generalized Curvilinear Advection Formalism For Finite Volume Codes Doing Relativistic Hydrodynamics, Jay Michael Call

LSU Doctoral Dissertations

While it is possible to numerically evolve the relativistic fluid equations using any chosen coordinate mesh, typically there are distinct computational advantages associated with different types of candidate grids. For example, astrophysical flows that are governed by rotation tend to give rise to advection variables that are naturally conserved when a cylindrical mesh is used. On the other hand, Cartesian-like coordinates afford a more straightforward implementation of adaptive mesh refinement (AMR) and avoid the appearance of coordinate singularities. Here it is shown that it should be possible to reap the benefits associated with multiple types of coordinate systems simultaneously in …