2007/09/17 by S. -K. Lee, M. V. Romalis · 1 citation
Physics and Astronomy · #physics.ins-det
paper · pdf · doi:10.1063/1.2885711
10 pages
arxiv created 2007/09/17 · arxiv updated 2009/12/01
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 non-magnetic conducting shells. A simple model is suggested to predict power-law decay of noise spectra beyond quasi-static regime. Our results can be used to assess noise from existing shields and to guide design of new shields for precision measurements.