Advanced Interferometer Control in the Presence of Radiation Pressure

Gravitational waves from binary black holes and neutron star mergers are being detected at an unprecedented rate. Gravitational wave observatories such as the Advanced LIGO detectors in Hanford, Washington, and Livingston, Louisiana continue to grow in sensitivity to signals from astrophysical origin by reducing noise to their fundamental limits. These detectors rely upon the ability to make heavy mirrors absolutely still, so when a very small gravitational wave passes through the detector, the extremely small relative motion imparted onto the mirrors by the gravitational wave is detectable. Current limitations to the sensitivity to gravitational waves depend significantly on the mass of the mirrors, including quantum radiation pressure noise and noise from the detector controllers pushing on the mirrors. One simple way to increase sensitivity to gravitational waves is to increase the mass of the mirrors. The team will train students in STEM research areas. This award supports the design of a LIGO upgrade to increase suspended test masses from 40 kg to 100 kg. In particular, the PI's team will contribute to the design of the enhanced actuation and calibration systems to accommodate the increased mass of the mirrors while taking full advantage of the sensitivity increases. This work will investigate the performance of the current 40 kg test mass suspensions, both in low-noise and lock acquisition configurations, which will inform simulations and designs of the 100 kg suspensions. The group will also investigate the feasibility of novel actuation schemes, including the possibility of remote test mass control using a high-power auxiliary laser upgrade to the photon calibrator, known as the photon actuator. This 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.