Using Nuclear Magnetic Moments to Search for Axionic Dark Matter

Abstract

Americium (241Am), with an unpaired proton in the F5/2 orbital, exhibits a significant magnetic dipole moment. It decays into an excited state of 237Np, leading to production of several detectable gamma emissions. The dipole moments of both 241Am and 237Np can be partially aligned at room temperature with the application of modest external magnetic fields (Bext), as little as 1-3G. When the magnetic field direction is rotated by 90°, the Bext-dipole interaction leads to a relative shifting of the energy spectrum for the emitted gammas, as measured by typical NaI or CeBr scintillating detectors, due to changes in the direction of the anisotropic emissions. This paper presents data taken as part of an experimental search for Axionic particles produced via a Primakoff coupling between photons and a magnetic field. The results show that the measured energy shifting, due to rotation of the magnetic field, was impacted by photons pass through the magnetic cavity upstream of the radioactive sample even though the photon beam was blocked from reaching the sample. Shining light through the magnetic field, while blocking the radioactive target, alters the value of the measured shifting. This experiment has been repeated several times with different detectors, sources and magnetic field configurations, yielding consistent results. Verification of these results will prove the production of Axions, Axion Like Particles (ALPs) or some beyond the Standard Model boson through the Primakoff mechanism for visible photons. As important, these results could establish the use of radioactive isotopes as detectors of Axionic, ALPs or other light bosons, candidates for future Dark Matter experimentation.