Earth-based gravitational waves interferometric detectors are shot-noise limited in the high-frequency region of their sensitivity band. While enhancing the laser input power is the natural solution to improve on the shot noise limit, higher power also increases the optical aberration budget due to the laser absorption in the highly reflective coatings of mirrors, resulting in a drop of the sensitivity of the detector. Advanced Virgo exploits Hartmann Wavefront Sensors (HWSs) to locally measure the absorption-induced optical aberrations by monitoring the optical path length change in the core optics. Despite the very high sensitivity of Hartmann sensors, temperature fluctuations can cause a spurious curvature term to appear in the reconstructed wavefront due to the thermal expansion of the Hartmann plate, that could affect the accuracy of the aberration monitoring. We present the implementation and validation of a control loop to stabilize the Advanced Virgo HWS temperature at the order of ΔT⩽0.01  K, keeping the spurious curvature within the detector’s requirements on wavefront sensing accuracy.

中文翻译：

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用于监测 Advanced Virgo 中像差的无热散焦 Hartmann 波前传感器


地基引力波干涉探测器的散粒噪声限制在其敏感带的高频区域。虽然提高激光输入功率是改善散粒噪声限制的自然解决方案，但由于反射镜的高反射涂层会吸收激光，较高的功率也会增加光学像差预算，从而导致探测器的灵敏度下降。 Advanced Virgo 利用哈特曼波前传感器 (HWS) 通过监测核心光学器件中的光路长度变化来本地测量吸收引起的光学像差。尽管哈特曼传感器的灵敏度非常高，但由于哈特曼板的热膨胀，温度波动可能会导致重建波前出现杂散曲率项，这可能会影响像差监测的准确性。我们提出了控制环路的实现和验证，以将 Advanced Virgo HWS 温度稳定在 ΔT⩽0.01 K 的量级，从而将杂散曲率保持在探测器对波前传感精度的要求范围内。