Parametric instability (PI), induced by the interaction between the cavity optical modes and acoustic modes of a mirror, is an inherent risk in interferometric gravitational wave detectors. The instability can result in exponential growth in acoustic mode amplitude and the saturation of detectors control systems. In this paper we analyse PI in the neutron star extreme matter observatory, a proposed high optical power (4.5 MW) detector, operating at cryogenic temperatures with silicon test masses (TMs), targeting high sensitivity between 1 and 4 kHz. Our results show that with current design parameters, approximately 16 unstable modes will arise per TM with maximum parametric gain ∼10. Varying the TM radius of curvature from the nominal values could eliminate PI, however not with current manufacture or actuator capability. PI mitigation will be required to suppress all unstable modes. This analysis identifies four optical modes and 16 acoustic modes dominating PI in NEMO paves the way for the design of PI mitigation strategies.

中文翻译：

---

中子星极端物质观测站的参数不稳定性

由反射镜的腔光学模式和声学模式之间的相互作用引起的参数不稳定性 (PI) 是干涉引力波探测器的固有风险。不稳定性会导致声学模式振幅呈指数增长和检测器控制系统饱和。在本文中，我们分析了中子星极端物质天文台中的 PI，这是一种拟议的高光功率 (4.5 MW) 探测器，使用硅测试质量 (TM) 在低温下运行，目标是 1 到 4 kHz 之间的高灵敏度。我们的结果表明，使用当前的设计参数，每个 TM 将出现大约 16 种不稳定模式，最大参数增益约为 10。改变标称值的 TM 曲率半径可以消除 PI，但不是当前制造商或执行器能力。需要 PI 缓解来抑制所有不稳定模式。该分析确定了 NEMO 中主导 PI 的四种光学模式和 16 种声学模式，为设计 PI 缓解策略铺平了道路。