Time-dependent spin dressing using a3He atomic beam

Abstract

We have performed high-precision experimental measurements of spin precession using a dressed 3 He atomic beam. Spin dressing uses an oscillating magnetic field that is both detuned to high frequency and orthogonal to a static magnetic field to effectively change the gyromagnetic ratio of a spin. We verify the validity of the spin-dressing Hamiltonian in regions beyond the limiting solution in which the Larmor frequency is much smaller than the frequency of the dressing field. We also evaluate the effect of magnetic field misalignment, i.e. if the oscillating magnetic field is not orthogonal to the static magnetic field. Modulation of the dressing-field parameters is also discussed, with a focus on whether such a modulation can be approximated merely as a time-dependent, dressed gyromagnetic ratio. Furthermore, we discuss implications for a proposed search for the neutron electric dipole moment, which would employ spin dressing to make the effective 3 He and neutron magnetic moments equal.

Electric dipole moments and the search for new physics

“…The nEDM@SNS experiment uses challenging technologies involving large-scale cryogenic systems (for the current experimental design, see Ahmed et al [149]). Considerable results have been obtained from the R&D efforts in all areas, including: polarized 3 He [170][171][172][173][174][175][176], dressed spins [177][178][179], magnetic field monitoring [180], non-magnetic feedthrough [181], SQUID based magnetometers [182], noble gas scintillation and its detection [183][184][185][186][187][188], electrical breakdown in LHe [150,151], HV generation in superfluid helium [189], cryogenic magnetic field studies [190], possible systematic effects [127,155,157,159,160,[191][192][193][194], and apparatus for studying spin dressing and systematic effects [138]. The SNS project is the only project making use of a superconducting shield, meaning it will not be affected by intrinsic fluctuations in the room temperature ferromagnetic shields, a technology which has not been tested at sensitivities below 10 −26 e • cm, and is relied on by all the other nEDM projects discussed above.…”

“…Nuclear Schiff moments and nuclear magnetic quadrupole moments give access to sources of hadronic parameters such as those discussed in Section III A [195,202,240]. These experiments include the CENTReX nuclear Schiff moment search utilizing TlF [287,288], nuclear magnetic quadrupole moment searches with 173 YbOH [289][290][291][292] and TaO + [293,294], and experiments with short-lived radioactive species such as RaF [295,296] and RaOCH + 3 [251,297], which are discussed in a later section. The accidental near-degeneracy of opposite parity states in 207 PbF provides a further experimental approach, especially in excited vibrational states [211].…”

Optically polarizedHe3

“…The cryogenic compatibility of 3 He is very attractive to co-locate with the neutrons, and the small 10% difference in the magnetic moments of 3 He and neutrons allows dressing techniques to give them effectively the same moment, thus allowing common-mode rejection of magnetic field noise (Golub and Lamoreaux, 1994). Recent experiments have shown the viability of this approach (Chu et al , 2011; Eckel et al , 2012). …”

The neutron electric dipole moment experiment at the Spallation Neutron Source

“…The polarized 3 He source will be a cryocooler based atomic beam, which was previously used in the experiments described in [68,69]. With a nozzle cooled to ≈ 1 K, a cold effusive source of 3 He atoms is produced.…”