Vibration analysis of KAGRA cryostat at cryogenic temperature
Vibration analysis of KAGRA cryostat at cryogenic temperature
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DOI：
10.1088/1361-6382/ac7cb5
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发表时间：
2022-03
影响因子：
3.5
通讯作者：
R. Bajpai;T. Tomaru;N. Kimura;T. Ushiba;Kazuhiro Yamamoto;Toshikazu Suzuki;T. Honda
中科院分区：
文献类型：
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作者：
R. Bajpai;T. Tomaru;N. Kimura;T. Ushiba;Kazuhiro Yamamoto;Toshikazu Suzuki;T. Honda
KAGRA使用低温技术将蓝宝石测试质量冷却至20 K，以减少热噪声。然而，低温恒温器的振动和结构共振与测试质量耦合，可能会污染探测器的灵敏度。我们对低温冷却系统进行了振动分析，以研究其对探测器灵敏度的影响。我们的测量表明，低于1hz的屏蔽振动不受制冷机操作或结构共振的影响，而是由地面运动主导。在1-100 Hz范围内，即使没有制冷机运行，盾构的本底噪声也比地震运动大2-3个数量级。制冷机的操作不会改变噪声底，但在整个频谱（1-100 Hz）上观察到2 Hz的峰值及其谐波。这些结果用于计算冷却系统振动与试验质量的耦合。我们得出结论，来自冷却系统的振动不会限制KAGRA设计的灵敏度。
KAGRA uses cryogenics to cool its sapphire test masses down to 20 K to reduce the thermal noise. However, cryocooler vibration and structural resonances of the cryostat couple to the test mass and can contaminate the detector sensitivity. We performed vibration analysis of the cooling system at cryogenic temperature to study its impact on detector sensitivity. Our measurements show shield vibration below 1 Hz is not impacted by cryocooler operation or structural resonances and is dominated by ground motion. The noise floor of the shield in the range 1–100 Hz was observed to be 2–3 orders of magnitude larger than seismic motion even without cryocooler operation. The operation of cryocoolers does not change the noise floor, but 2 Hz peaks and their harmonics were observed over the entire spectrum (1–100 Hz). These results were used to calculate the coupling of cooling system vibration to the test mass. We conclude that vibration from the cooling system does not limit KAGRA design sensitivity.