magnetic field homogenization; vector magnetometry; neutron electric dipole moment
Abel C., Afach S., Ayres N. J., Ban G., Bison G., Bodek K., Bondar V., Chanel E., Chiu P.-J., Crawford C. B., Chowdhuri Z., Daum M., Emmenegger S., Ferraris-Bouchez L., Fertl M., Franke B., Griffith W. C., Grujić Z. D., Hayen L., Hélaine V., Hild N., Kasprzak M., Kermaidic Y., Kirch K., et al. (2020), Optically pumped Cs magnetometers enabling a high-sensitivity search for the neutron electric dipole moment, in Physical Review A
, 101(5), 053419-053419.
Abel C., Afach S., Ayres N. J., Baker C. A., Ban G., Bison G., Bodek K., Bondar V., Burghoff M., Chanel E., Chowdhuri Z., Chiu P.-J., Clement B., Crawford C. B., Daum M., Emmenegger S., Ferraris-Bouchez L., Fertl M., Flaux P., Franke B., Fratangelo A., Geltenbort P., Green K., Griffith W. C., et al. (2020), Measurement of the Permanent Electric Dipole Moment of the Neutron, in Physical Review Letters
, 124(8), 081803-081803.
Abel Christopher, Bison Georg, Griffith W. Clark, Heil Werner, Kirch Klaus, Koch Hans-Christian, Lauss Bernhard, Mtchedlishvili Alexander, Pototschnig Martin, Schmidt-Wellenburg Philipp, Schnabel Allard, Pais Duarte, Voigt Jens (2019), PicoTesla absolute field readings with a hybrid 3He/87Rb magnetometer, in The European Physical Journal D
, 73(7), 150-150.
Abel C., Ayres N. J., Baker T., Ban G., Bison G., Bodek K., Bondar V., Crawford C. B., Chiu P.-J., Chanel E., Chowdhuri Z., Daum M., Dechenaux B., Emmenegger S., Ferraris-Bouchez L., Flaux P., Geltenbort P., Green K., Griffith W. C., van der Grinten M., Harris P. G., Henneck R., Hild N., Iaydjiev P., et al. (2019), Magnetic-field uniformity in neutron electric-dipole-moment experiments, in Physical Review A
, 99(4), 042112-042112.
Ban G., Bison G., Bodek K., Daum M., Fertl M., Franke B., Grujić Z.D., Heil W., Horras M., Kasprzak M., Kermaidic Y., Kirch K., Koch H.-C., Komposch S., Kozela A., Krempel J., Lauss B., Lefort T., Mtchedlishvili A., Pignol G., Piegsa F.M., Prashanth P., Quéméner G., Rawlik M., et al. (2018), Demonstration of sensitivity increase in mercury free-spin-precession magnetometers due to laser-based readout for neutron electric dipole moment searches, in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detector
, 896, 129-138.
Bison G., Bondar V., Schmidt-Wellenburg P., Schnabel A., Voigt J. (2018), Sensitive and stable vector magnetometer for operation in zero and finite fields, in Optics Express
, 26(13), 17350-17350.
Our collaboration, which consists of 15 institutions, uses a magnetic resonance experiment at PSI to search for the electric dipole moment of the neutron (nEDM). The existence of a finite neutron EDM dn, which is predicted by many theories beyond the standard model of particle physics (TBSM), has not yet been confirmed. The current best upper limit of dn < 3E-26 e·cm significantly restricts the parameter space of many TBSM. Since improved limits on dn or a discovery of a finite value would be a powerful guide in the development of a TBSM, the neutron EDM is deemed one of the most sensitive tests of physics beyond the standard model. As a consequence, several collaborations around the world currently compete to realize a next-generation nEDM experiment with planned sensitivities in the E-27 e·cm to E-28 e·cm range.One of the most important design criteria for an improved nEDM experiment is the realization of a stable and homogeneous main magnetic field B0. The level at which B0 can be controlled or measured is directly linked to the achievable nEDM sensitivity since uncompensated B0 fluctuations add noise to the extracted nEDM value and field inhomogeneities give rise to several systematic effects. The primary goal of this project is to realize a magnetic environment which is stable and homogeneous enough to reach the dn < E-27 e·cm level. Neutron EDM experiments must use a wide range of techniques to meet those increasing demands on B0 control. The work proposed here focusses on Cs magnetometers that are developed at PSI and in the nEDM collaboration since several years.Assuming typical experimental conditions, the uncompensated magnetic field fluctuations in each experimental cycle must be smaller than 10 fT in order to achieve a limit of dn < E-27 e·cm after two years of data taking. We propose to develop an nEDM analysis method that uses Cs magnetometers to measure the field fluctuations, which requires a corresponding stability of the sensors.In 2016 we confirmed a systematic error in nEDM measurements with a Hg co-magnetometer caused by cubic gradients. Due to the symmetry of the gradient field it cannot be detected with large-volume magnetometers. A spatially resolved mapping of the field with many accurate sensors is necessary to suppress the effect. The estimated requirements for sensor accuracy of 0.5 pT are significantly higher than previously assumed. For that reason we propose to investigate magnetometers based on atomic alignment and linearly polarized light, which suppress many systematic magnetometer errors. Our previous methods on vector magnetometry and free spin precession will be transferred to spin alignment.We demonstrated that a field homogenization based on Cs magnetometer readings significantly in- creases the sensitivity of our current nEDM experiment. The proposed work will enable field homogenization with an array of Cs vector magnetometers that can measure and compensate magnetic field gradients. We expect to achieve a level of performance that will permit a search for a nEDM with a sensitivity much better than E-27 e·cm. The project will have a significant impact on the sensitivity and the control of systematic errors of our next-generation neutron EDM experiment. It is a key ingredient in that experiment which could lead to the first discovery of an EDM in a non-degenerate system.