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 Cs133 magnetometers and Hg199 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 4×10-28ecm in a single measurement; therefore, the use of economically and mechanically favored solid aluminum electrodes is possible.
|Journal||Physical Review A|
|State||Published - Jun 2021|
Bibliographical noteFunding Information:
We would like to thank A. Crivellin and M. Spira for helpful discussions. We are grateful for the technical support from P. Hömmen and R. Körber with the material measurements in BMSR-2, PTB, Berlin. The material measurements inside BMSR-2 were supported by the Core Facility “Metrology of Ultra-Low Magnetic Fields” at PTB funded by Deutsche Forshungsgemeinschaft (DFG) through funding codes DFG KO 5321/3-1 and TR408/11-1. The swiss members acknowledge the financial support from the Swiss National Science Foundation through Projects No. 157079, No. 163413, No. 169596, No. 188700 (all PSI), No. 181996 (Bern), No. 172639 (ETH), and No. FLARE20FL21-186179. This work has also been supported by the Cluster of Excellence “Precision Physics, Fundamental Interactions, and Structure of Matter” (PRISMA EXC 2118/1) funded by DFG within the German Excellence Strategy (Project ID 39083149) from Johannes Gutenberg University Mainz. This work is also supported by Sigma Xi Grants No. G2017100190747806 and No. G2019100190747806, and by the award of the Swiss Government Excellence Scholarships (SERI-FCS) No. 2015.0594. The group from Jagellionian University Cracow acknowledges the support from National Science Centre, Poland, through Grants No. 2018/30/M/ST2/00319, and No. 2020/37/B/ST2/02349. The group from University of Leuven acknowledges supports from the Fund for Scientific Research Flanders (FWO).
© 2021 American Physical Society.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics