Magnetic Johnson-Nyquist noise (JNN) originating from metal electrodes, used to create a static electric field in neutron electric-dipole-moment (nEDM) experiments, may limit the sensitivity of measurements. We present here a dedicated study on JNN applied to a large-scale long-measurement-time experiment with the implementation of a comagnetometry. In this study, we derive surface- and volume-averaged root-mean-square normal noise amplitudes at a certain frequency bandwidth for a cylindrical geometry. In addition, we model the source of noise as a finite number of current dipoles and demonstrate a method to simulate temporal and three-dimensional spatial dependencies of JNN. The calculations are applied to estimate the impact of JNN on measurements with the new apparatus, n2EDM, at the Paul Scherrer Institute. We demonstrate that the performances of the optically pumped ${}^{133}\mathrm{Cs}$ magnetometers and ${}^{199}\mathrm{Hg}$ comagnetometers, which will be used in the apparatus, are not limited by JNN. Further, we find that, in measurements deploying a comagnetometer system, the impact of JNN is negligible for nEDM searches down to a sensitivity of $4\times {10}^{-28}e\mathrm{cm}$ in a single measurement; therefore, the use of economically and mechanically favored solid aluminum electrodes is possible.

中文翻译：

---

中子电偶极矩实验中的约翰逊-奈奎斯特噪声效应

源自金属电极的磁性约翰逊-奈奎斯特噪声 (JNN)，用于在中子电偶极矩 (nEDM) 实验中产生静电场，可能会限制测量的灵敏度。我们在此介绍了一项关于 JNN 的专门研究，该研究适用于实施彗磁测量的大规模长测量时间实验。在这项研究中，我们导出了圆柱几何体在特定频率带宽下的表面和体积平均均方根法向噪声幅度。此外，我们将噪声源建模为有限数量的电流偶极子，并演示了一种模拟 JNN 的时间和三维空间依赖性的方法。这些计算用于估计 JNN 对使用新设备 n2EDM 进行测量的影响，在 Paul Scherrer 研究所。${}^{133}\mathrm{CS}$ 磁力计和 ${}^{199}汞$将在设备中使用的电磁磁力计不受 JNN 的限制。此外，我们发现，在部署一个电磁计系统的测量中，JNN 对 nEDM 搜索的影响可以忽略不计，灵敏度低至$4\times {10}^{-28}\mathrm{电子}\mathrm{厘米}$在一次测量中；因此，使用经济上和机械上有利的实心铝电极是可能的。