[论文解读] First Results of GINGERino, a deep underground ringlaser

Jacopo Belfi, N. Beverini+12 more|arXiv (Cornell University)|Jan 12, 2016

Geophysics and Sensor Technology参考文献 13被引用 3

一句话总结

GINGERino，一个安装在格兰萨索国家实验室（LNGS）深处的3.6米见方环形激光器，展示了在短积分时间内亚10⁻¹⁰ rad/s的灵敏度，验证了该地点在未来的Lense–Thirring效应测试中具备低噪声潜力。尽管受到气压引起的低频噪声挑战，该仪器证实了在地下环境中长期、高稳定性旋转测量的可行性。

ABSTRACT

Large ring-laser gyroscopes are capable of measuring angular rotations with a precision well below fractions of $prad/s$, not far from $10^{-14}$ $rad/s$, the accuracy required for General Relativity tests, this is what the GINGER (Gyroscope-IN-GEneral-Relativity) experiment is aiming for. These features do not guarantee the possibility of measuring the General Relativity Lense--Thirring effect, that manifests itself as a tiny ($\approx 10^{-9} imes Ω_E$) perturbation of the Earth rotation rate. An underground location being in principle less affected by external local disturbances represents a good candidate for housing such a challenging experiment. GINGERino is a test apparatus to investigate the residual local disturbances in the most inner part of the underground international laboratory of the GranSasso (LNGS). It consists of a square ring laser with a $3.6$ m side. The instrument has been tailored to be the larger allowed by the particular location inside the laboratory. Its main objective is to measure the very low frequency rotational motions, in order to prove that LNGS is a suitable location for very low noise measurements and, possibly, General Relativity tests. Aside this main goal, GINGERino will provide unique data for geodesy and geophysics. Its installation has been completed during 2015. Since then, several long set of data have been collected, and the apparatus has been continuously running unattended for more than one week. The typical power spectrum sensitivity was a few $ 10^{-10} rad/s/\sqrt(Hz)$, with integration time not longer than tens of seconds. Improvements of the apparatus are ongoing in order to improve the integration time.

研究动机与目标

• 评估格兰萨索地下实验室（LNGS）是否适合部署高精度GINGER实验，以探测Lense–Thirring效应。
• 利用紧凑型环形激光陀螺仪在受控地下环境中测量地球的极低频旋转运动。
• 识别并表征可能限制长期稳定性和灵敏度的局部环境扰动，尤其是气压和地震噪声。
• 验证实现广义相对论环形激光陀螺仪测试所要求的10⁻¹⁴ rad/s灵敏度的技术可行性。
• 通过高灵敏度环形激光器的连续、无人值守运行，提供独特的大地测量与地球物理数据。

提出的方法

• 将3.6米见方的环形激光腔体部署在LNGS地下实验室最深处，以最大限度减少地表扰动。
• 采用基于萨尼亚克效应的环形激光器，通过顺行与逆行光束的频率差测量相对于惯性系的旋转速率。
• 同步采集共置地震仪和环境监测设备（气压、温度）的数据，以关联噪声源。
• 通过功率谱和地震噪声的偏振特性分析，识别方向性噪声源，特别是沿隧道轴向的噪声。
• 应用时频（TF）分析，检测气压波动与低频地震噪声之间的相关性。
• 实施机械改进措施，以提高腔体光子寿命和镜面质量，从而增强灵敏度。

实验结果

研究问题

• RQ1 格兰萨索地下站点能否支持探测Lense–Thirring效应所必需的超低噪声环境？
• RQ2 大气压变化在多大程度上会诱导环形激光器和地震仪测量中的低频噪声？
• RQ3 观测到的水平地震噪声是否具有方向性，并与隧道轴向的气流相关，表明其起因为气压驱动？
• RQ4 环形激光器能否实现足够的积分时间与稳定性，以在10⁻¹⁴ rad/s量级上测量地球自转速率？
• RQ5 局部环境扰动（如气压、温度和水文变化）如何影响环形激光器测量的长期稳定性？

主要发现

• GINGERino在积分时间不超过数十秒时，典型功率谱灵敏度达到数×10⁻¹⁰ rad/s/√Hz。
• 机械升级后，腔体光子寿命从约240 μs提升至约150 μs，表明腔体稳定性有所改善。
• 在地震仪的水平分量中观测到沿隧道轴向的低频噪声过量，提示空气运动可能是噪声源。
• 时频分析显示，气压波动（具有昼夜和工作日/周末周期）与水平地震噪声存在强烈相关性。
• GINGERino实验室内气压变化表现出明显的昼夜和周周期调制，振幅达约1 kPa/100，与地震噪声峰值同步。
• 数据表明，气压波动是低频噪声的主要来源，因此可能需要对腔体室进行气密隔离以抑制该效应。