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Study of low-loss materials for mirrors used in the next-generation gravitational wave detectors

下一代引力波探测器反射镜低损耗材料研究

基本信息

批准号：
13440070
负责人：
TSUBONO Kimio
金额：
$ 8.51万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13440070/
关键词：
gravitational wave laser interferometer mirror fused silica low-loss mono-crystalline thermal noise precise measurement

项目摘要

Investigating the mechanical loss of low-loss samples has been an important, but difficult, subject in the field of detecting gravitational-waves. The thermal motion of the internal mode of the mirrors is considered to be one of the fundamental noise sources which limits the sensitivities of gravitational-wave detectors. The amplitude of the thermal motion is proportional to the square root of the mechanical loss of the mirror. Therefore, it is significant to investigate the intrinsic loss of the materials for the mirror to estimate the sensitivity limit of gravitational-wave detectors, and to improve it by finding lower loss materials. However, the loss of low-loss samples is difficult to measure because of the loss due to the support for the measurement.We have developed a method to measure the mechanical loss of cylindrical samples. By using our nodal support technique, the loss due to the support can be excluded. We evaluated separately the intrinsic loss of the material and the loss due to the surface roughness by systematically analyzing the measured losses.Then, we measured the mechanical loss of crystalline anisotropic samples, silicon and sapphire, using a nodal support. Measured quality factor of the silicon sample reached 1.0 x 10^8 at room temperature. The sapphire sample showed lower quality factors, 6.4 x 10^7 at most, which were analytically confirmed to be dominated by surface loss.Also, we systematically measured and compared the mechanical-losses of various kinds of bulk fused silica. Their quality factors widely ranged from 7 x 10^5 to 4 x 10^7, the latter being the highest reported among fused silica mirror substrates. We observed the frequency dependence of Qs. We also found increase in Qs by an annealing.

研究低损耗样品的机械损耗一直是引力波探测领域的一个重要但困难的课题。镜子内模的热运动被认为是限制引力波探测器灵敏度的基本噪声源之一。热运动的幅度与镜子的机械损耗的平方根成正比。因此，研究反射镜材料的固有损耗对于估计引力波探测器的灵敏度极限，并通过寻找更低损耗的材料来改进它具有重要意义。然而，低损耗样品的损耗由于测量的支撑而导致的损耗很难测量。我们开发了一种测量圆柱形样品机械损耗的方法。通过使用我们的节点支撑技术，可以排除支撑造成的损失。通过系统分析测量的损耗，我们分别评估了材料的固有损耗和表面粗糙度造成的损耗。然后，我们使用节点支撑测量了晶体各向异性样品、硅和蓝宝石的机械损耗。室温下测得硅样品的品质因数达到1.0 x 10^8。蓝宝石样品的品质因数较低，最多为 6.4 x 10^7，分析证实其主要由表面损耗决定。此外，我们系统地测量和比较了各种块状熔融石英的机械损耗。它们的品质因数范围从 7 x 10^5 到 4 x 10^7，后者是熔融石英镜基材中报道最高的。我们观察了 Q 的频率依赖性。我们还发现退火会增加 Q 值。