Calculation of magnetic field noise from high-permeability magnetic shields and conducting objects with simple geometry

S. K. Lee, M. V. Romalis

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

High-permeability magnetic shields generate magnetic field noise that can limit the sensitivity of modern precision measurements. We show that calculations based on the fluctuation-dissipation theorem allow quantitative evaluation of magnetic field noise, either from current or magnetization fluctuations, inside enclosures made of high-permeability materials. Explicit analytical formulas for the noise are derived for a few axially symmetric geometries, which are compared with results of numerical finite element analysis. Comparison is made between noises caused by current and magnetization fluctuations inside a high-permeability shield and also between current-fluctuation-induced noises inside magnetic and nonmagnetic conducting shells. A simple model is suggested to predict power-law decay of noise spectra beyond a quasi-static regime. Our results can be used to assess noise from existing shields and to guide design of new shields for precision measurements.

Original languageEnglish (US)
Article number084904
JournalJournal of Applied Physics
Volume103
Issue number8
DOIs
StatePublished - May 9 2008

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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