RUI -- Further Optical Charge Studies with the Trinity University Kelvin Probe

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The Laser Interferometer Gravitational-Wave Observatory (LIGO) is most sensitive to gravitational waves at signal frequencies near 100 Hz. One potential noise source at these frequencies is the motion of surface charge on optics, which can be generated through abrasive contact with dust, contact with other materials, or possibly from polarization by an electrostatic drive. Charge contributes noise by interfering with the position control of optics, attracting dust to the optical surface, and generating fluctuating electric fields. The noise contribution depends on the charge magnitude and the correlation time for charge motion. Reasonable values for these quantities suggest that charging might be a limiting noise source for Advanced LIGO. This award supports a research program with the goal of exploring the underlying physics of dielectric charging and methods to mitigate its impact on Advanced LIGO. The laboratory at Trinity University developed by the PI through prior NSF support will be used for a number of experiments including various ways Advanced LIGO components might produce electrostatic charging, testing methods to mitigate the charging, and studying how charging actually produces noise in gravitational wave detectors. This research could be of crucial importance to Advanced LIGO, due to the charge noise witnessed at LIGO Livingston Observatory in 2006 and the recent discovery of charging from exposure to an electrode similar to one of those in Advanced LIGO. The research is also important for other existing, future, and envisioned ground-based gravitational wave interferometers in order to reduce noise in their most sensitive frequency range. In addition, continued charging research at Trinity University provides a real-word research experience to undergraduates in a cutting-edge field; over a dozen Trinity students have participated in LIGO-related projects and theses, have been published authors, have presented their results at state and national meetings, have won awards for their accomplishments, and have moved on to successful physics-related careers.