Sensors for Low-Frequency Improvements in Advanced LIGO

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This award supports research in gravitational physics instrumentation, and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. The project aims at the development of high-precision sensors, such as a compact inertial tilt sensor, to improve the low-frequency sensitivity and robustness of LIGO. Improvement in LIGO's sensitivity will lead to the detection of gravitational waves (GW) from heavier binary sources and improved signal to noise ratio. Making LIGO robust against harsh environmental conditions, such as wind and earthquakes, improves the duty cycle for GW observation, leading to more detections, which will in turn increase the rate of new discoveries from GW science. The tilt sensors will have a broader impact in areas such as seismology and geophysics by enabling measurement of tele-seismic tilts and tilt-free ground acceleration at frequencies as low as 10 mHz. The high precision angle readouts developed for these tilt sensors have a wide variety of applications in metrology and precision experiments. This award not only supports the development of devices for Advanced LIGO, but it also serves to maintain and strengthen synergistic activities of the table-top gravity group with the gravitational wave detection community. Importantly, this STEM research will train undergraduate and graduate students in building precision mechanical instruments for fundamental research.Environmental conditions such as high wind, microseism and earthquakes continue to affect duty cycle and add noise to the LIGO detectors. This is primarily due to the inability of seismometers to distinguish between low-frequency tilt and translation, known as tilt-horizontal coupling. The ground-tilt sensors the group has developed are already improving the low-frequency seismic isolation in LIGO. Making them smaller, more sensitive with interferometric readouts and compatible with LIGO vacuum requirements, would allow them to be mounted directly on the isolated platforms from which the main mirrors are suspended, reducing the low-frequency angular motion of the platform by more than two orders of magnitude. In addition, the group will also research sensors for Newtonian noise reduction and a Gravitational calibrator to improve the absolute accuracy of GW measurementsThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.