This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This award extends the Stanford LIGO group's ongoing program on advanced gravitational wave detectors to address risk mitigation for Advanced LIGO and to provide research for enhancements to Advanced LIGO to increase observatory sensitivity. In particular, research will focus on improved optical coatings, control of electrostatic charging, and tilt sensing for the seismic isolation system. (1) The team will include new expertise in NMR spectroscopy of amorphous oxides in the earth's crust and Raman spectroscopy, to obtain micro-structural information on bond configurations in the selected coating materials. Thermal noise due to mechanical noise in these coatings will limit the sensitivity of any future interferometer beyond Advanced LIGO. Thus the goal of this research is to understand the physics of the mechanical loss mechanisms so that we can inform other researchers in the LIGO Scientific Collaboration (LSC) on the mitigation of this noise source. (2) The team will also work with the LSC to develop requirements for a charge management system for Advanced LIGO. Scaling arguments will be used to predict which sources of potential electrostatic charge accumulations might be dominant. Numerical calculations will prioritize them and identify those that merit full finite-element modelling of their contribution to the noise budget. Development of mitigation techniques will include research on alkali ion in-diffusion to achieve weakly conducting test mass surfaces that will allow spurious surface charges to relax to equipotentials without impacting the optical and mechanical coating losses. A localized UV LED conduction channel to allow passive charge equilibration between the test mass and the grounded frame without damage to the UV-sensitive optical coatings will be evaluated. 3) Research will be initiated to develop improved tilt sensors for increasing the performance of the active seismic isolation systems in Advanced LIGO using externally excited, passive ring optical gyroscopes which could be used to directly measure the ground rotations and improve the performance of the isolation systems which would lead to improved operational reliability of Advanced LIGO. This research program includes participation from many disciplines including mechanical, electrical and control engineers, physicists and materials researchers. The nature of this multidisciplinary effort makes it ideal for training graduate students. High school students and university undergraduates are encouraged to participate in these projects, integrating research and education. In addition, the program will develop and transfer technologies to the commercial stream.
