A Tilt-Free Seismometer for Advanced Gravitational-Wave Detectors

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This project is jointly funded by the LIGO Research Program (Physics Division) and the Experimental Program to Stimulate Competitive Research (EPSCoR). This is an exciting time for the maturing field of gravitational-wave physics. Construction of Advanced LIGO (the Laser Interferometer Gravitational-wave Observatory), an overhaul of the Initial LIGO interferometers, is now complete and the first couple months of data have been collected. The advanced detectors made last year the first direct detection of gravitational waves, a momentous event that will transform our understanding of the universe and marks the beginning of a new field of gravitational wave astronomy. Predicted by Einstein nearly 100 years ago, gravitational waves are distortions of space-time created by the movements of massive astrophysical objects such as exploding stars and coalescing black holes or neutron stars. The effect of gravitational waves on space-time is minuscule, however, and necessitates the design and construction of detectors that push the limits of precision measurement techniques. This award supports research to improve the Advanced LIGO sensitivity at low frequencies and increase the amount of time the detector is collecting science quality data. In addition, this program will serve as an invaluable training ground for undergraduate and graduate students who will develop scientific skills from a diverse set of disciplines and prepare them to fill positions in academia and industry. The group is strongly committed to sharing the excitement of the field with the public through outreach at all levels, reaching out in particular to the communities in Mississippi.Gravitational waves can be detected by using laser light to measure infinitesimal changes in the distance between mirrors located two-and-a-half miles (4 km) away from one another. The mirrors are suspended as pendulums to isolate them from all vibrations other than the gravitational wave. The Advanced LIGO detectors have achieved a sensitivity to changes in the distance between the mirrors of better than one-ten-thousandth the diameter of a proton. There nonetheless remain many challenges to further improve the interferometers in order to increase the rate of gravitational wave detections and expand the spectrum of astrophysical objects that can be observed. One such challenge arises from the design of the commercial seismometers that are used to provide active vibration isolation of the mirrors. The seismometers cannot distinguish between horizontal acceleration of the ground and tilt of the ground. This award supports the development of a high precision tilt-free seismometer to improve the Advanced LIGO seismic isolation. The project includes deriving updated requirements for a tilt-free seismometer based on data from the observatories, designing and modeling the instrument, constructing and measuring the performance of the tilt-free seismometer and conducting a theoretical and experimental noise analysis of the system.