分类: 物理学 >> 核物理学 提交时间: 2024-06-11
摘要: 高能光子源 (HEPS) 对存储环板的振动水平有严格的限制。如果振动水平超过规格限值,会影响设备的正常运行,影响实验终端的采样效率。随着周边城市基础设施建设的不断扩大,为了控制外部振动源,有必要研究HEPS场地的振动传播特性。为了评估外部振动对HEPS关键组件的影响,已经进行了一系列测量。振动台用于人工生成频率为 7Hz 至 100 Hz 的垂直正弦激励。沿裸露地面测量振动响应,分析不同频率的振动衰减。根据测量数据的拟合结果,得到衰减公式和关键参数范围。同时,通过在HEPS现场行驶的50吨起重机的振动数据验证了衰减公式。测量数据与上述拟合公式非常吻合。测量数据与拟合曲线之间的差异在 $35 %$ 以内。本研究将为HEPS校园周边外部行驶载荷的相关调控奠定基础,同时为地面振动传播的研究方法提供参考。
分类: 物理学 >> 核物理学 提交时间: 2023-07-02
摘要: Significant evidence for a gravitational-wave background was reported by several pulsar-timing-array collaborations. By assuming that this signal is interpreted by the scalar-induced gravitational waves, we study physical implications of the observed signal for the nature of primordial curvature perturbations and primordial black holes. In particular, we explore the effects of primordial non-Gaussianity on the inferences of model parameters, and obtain the parameter region allowed by the observed signal, i.e., the primordial scalar spectral amplitude $A_S\sim10^{-2}-1$, the primordial non-Gaussian parameter $-10\lesssim f_{\mathrm{NL}} \lesssim 10$, and the mass of primordial black holes $m_{\mathrm{pbh}}\sim10^{-3}-0.1M_{\odot}$. We find that the non-Gaussianity suppressing the abundance of primordial black holes is preferred by the observed signal. We show that the anisotropies of scalar-induced gravitational waves are a powerful probe for measurements of the non-Gaussian parameter $f_{\mathrm{NL}}$, and conduct a complete analysis of the angular power spectrum in the nano-Hertz band. We expect that the Square Kilometre Array project has potentials to measure such anisotropies.