A general method for computing thermal magnetic noise arising from thin conducting objects

Thermal motion of charge carriers in a conducting object causes magnetic field noise that may interfere with sensitive measurements near the object. In this paper, we describe a method to compute the spectral properties of the thermal magnetic noise from arbitrarily shaped thin conducting objects. The method is based on modeling divergence-free currents on a conducting surface using a stream function and calculating the magnetically independent noise-current modes. By doing this, we obtain the power spectral density of the thermal magnetic noise as well as its spatial correlations and frequency dependence. We also describe a numerical implementation of the method and verify it against analytic formulas. We provide the implementation as a part of the free and open-source software package bfieldtools.

Automated summary

This paper presents a method to compute the spectral properties of thermal magnetic noise in conducting objects, by modeling divergence-free currents on the object's surface to calculate magnetically independent noise-current modes. The power spectral density, spatial correlations, and frequency dependence of thermal magnetic noise are obtained through this method, which is also implemented numerically and validated against analytic formulas. The implementation is provided as part of the open-source software package bfieldtools.