Research on the Thermal Correction System and Thermal Coating Noise

先进的LIGO是一台巨大的激光干涉仪，很可能是第一台探测引力波的仪器。打开这扇通往宇宙的全新窗口，是近期最令人期待的科学事件之一。但高级LIGO只有在能够补偿和校正仪器内部所有光学部件中的所有静态和动态曲率半径误差的情况下才能成功。否则，这些曲率误差将降低干涉仪内部的对比度，增加损耗和噪声，并限制高级LIGO的覆盖范围。这些曲率误差将由制造商造成，他们在抛光和镀膜过程中对表面形状的控制有限，以及光学元件内部的温度梯度将由残留的激光束吸收引起。热补偿系统(TCS)负责测量和修正这些误差。TCS在每个反射镜周围使用环形加热器来改变它们的曲率半径，并使用激光投影系统将特定的加热图案写入光学系统，以补偿基片内部的热透镜。该奖项支持一个小型试验台，用于开发和测试TCS，分析对TCS的要求，并就这一重要子系统对学生进行培训。先进的LIGO将受到形成干涉仪内反射镜介质涂层的原子的布朗运动的限制。虽然涂层热噪声的理论已经很好地建立了，但这种噪声的大小取决于几个不太了解的材料参数。对噪声的直接测量很少，几乎不是系统的，而且从未在高级LIGO频段进行过。该奖项还将支持一项致力于测量不同涂层、衬底和不同光束尺寸的热涂层噪声的实验，以详细研究整个Advanced LIGO频段的热涂层噪声。探测引力波对天体物理和天文学的重要性怎么估计都不为过。这些波是由移动的质量引起的，这些质量改变了时空的曲率。这种变化以引力波的形式在空间中传播。这些波是宇宙中速度限制的直接结果，它们的确切形式由爱因斯坦的广义相对论描述。打开这扇通往宇宙的全新窗口，将允许研究许多有趣的天文物体背后的物理现象，如中子星、黑洞、双星或超新星。然而，达到预期灵敏度的实验挑战为研究生和年轻科学家提供了一个理想的训练场地。这些学生将通过在高级LIGO环境下进行小型但具有挑战性的实验室实验来获得宝贵的技能。

Advanced LIGO is a gigantic laser interferometer that is likely be the first instrument to detect gravitational waves. Opening this completely new window to the universe is one of the most anticipated scientific events in the near future. But Advanced LIGO will only be successful if it is possible to compensate and correct all static and dynamic radii of curvature errors in all optical components inside the instrument. These curvature errors would otherwise reduce the contrast inside the interferometer, increase the losses and the noise, and limit the reach of Advanced LIGO. These curvature errors will be caused by manufacturers who have limited control over the surface figure during polishing and coating of the optics and by thermal gradients inside the optics which will be caused by residual laser beam absorption. The thermal compensation system (TCS) is responsible for measuring and correcting these errors. The TCS uses ring heaters around each mirror to change their radii of curvatures and a laser projection system to write a specific heating pattern into the optic to compensate the thermal lens inside the substrate. This award supports a small testbed to develop and test the TCS, analyze the requirements to be imposed on the TCS, and train students on this important subsystem. Advanced LIGO will be limited by the Brownian motion of the atoms which form the dielectric coatings of the mirrors inside the interferometer. Although the theory of coating thermal noise is well established, the magnitude of such noise depends on several less well understood material parameters. Direct measurements of the noise are rare, hardly systematic, and have never been done across the Advanced LIGO frequency band. This award will also support an experiment dedicated to measure thermal coating noise for different coatings, substrates, and different beam sizes to study thermal coating noise in great detail and across the entire Advanced LIGO frequency band.The importance of the detection of gravitational waves for astrophysics and astronomy can hardly be overestimated. These waves are caused by moving masses which change the curvature of spacetime. This change propagates through space in the form of gravitational waves. These waves are a direct consequence of the speed limit in the universe and their exact form is described by Einstein's theory of general relativity. Opening this completely new window to the universe will allow study of the physics behind many interesting astronomical objects such as neutron star or black hole binaries or supernovae. However, the experimental challenges to reach the expected sensitivity present an ideal training ground for graduate students and young scientists. These students will gain valuable skills by working on a small but challenging laboratory experiment within the context of Advanced LIGO.