An RUI Proposal to Study Thermal Noise and Bilinear Noise in LIGO and Advanced LIGO

该奖项支持克服有望限制先进LIGO灵敏度的噪声源的研究。先进LIGO最初使用的高折射率涂层材料是热噪声的主要来源。过去的研究确定了低折射率涂层材料中过量损耗的来源，从而证明了如何减少或消除损耗。这些对低折射率材料的研究提供了重要的指标，以指导寻找必要的高折射率但机械损耗低的涂层。LIGO科学家已经研究并减少了直接耦合到干涉仪的大量噪声源，从而暴露了间接的双线性噪声过程，例如在LIGO敏感频率波段外产生的噪声上转换到该波段。双相干提供了这种双线性耦合的测量，同时对高斯噪声不敏感。根据这项拨款，将继续研制双一致性数据监测仪。一旦识别出来，就可以监控这种噪音，如果可能的话，还可以消除这种噪音。双相干计算引擎最终可以用于搜索引力波，因为激发信号和爆发信号都具有非零双相干性。先进的LIGO计划在2015年全面投入使用，其设计的灵敏度使其能够定期观测引力波。通过改进光学涂层和改善上转换噪声来提高高级LIGO的灵敏度，将实现最大的发现潜力。PI计划让几名本科生参与他的研究。这与霍巴特和威廉史密斯9hw50学院正在努力扩大他们的科学项目非常吻合。在HWS的LIGO等研究项目中工作的机会有助于增加物理学专业的人数，并改变他们对物理学职业的态度。

This award supports research to overcome noise sources that are expected to limit the sensitivity of Advanced LIGO. The high-index of refraction coating material to be used initially in Advanced LIGO is the main source of thermal noise. Past research to determined the source of excess loss in a low-index coating material allowed demonstration of how it may be reduced or eliminated. These studies of low-index material provided important indicators to guide the search for the necessary high-index coating but with low mechanical loss. LIGO scientists have studied and reduced the multitude of sources of noise that directly couple into the interferometer, thereby exposing indirect, bilinear noise processes, such as up-conversion of noise produced outside LIGO's band of sensitive frequencies into that band. Bicoherence provides a measure of such bilinear coupling while being insensitive to Gaussian noise. Development of a data monitor for bicoherence will continue under this award. Once identified, this noise can be monitored and if possible, eliminated. The bicoherence calculation engine could be adapted eventually to search for gravitational waves, since inspiral and burst signals both have nonzero bicoherence.Advanced LIGO, which is scheduled to be fully operational by 2015, has been designed with a sensitivity to allow it to make regular observations of gravitational waves. Improvement in Advanced LIGO sensitivity through improved optical coatings and amelioration of up-conversion noise will allow achievement of the greatest discovery potential. The PI plans to involve several undergraduates in his research. This matches well with Hobart and William Smith 9HWS0 Colleges' ongoing effort to expand their science program. The opportunity to work in research programs like LIGO at HWS is helping to increase the number of physics majors and to change their attitude about a career in physics.