| Results are given from the next-generation search for T-violation in 205Tl, which is interpreted in terms of an electric dipole moment of the electron (de) using theory. The new experiment is a major upgrade of the apparatus used to set the previous best limit on de. Like its predecessor, it uses magnetic resonance with separated oscillating fields, laser optical pumping for state selection and analysis, and counter-propagating vertical atomic beams to control systematic effects arising from motional magnetic fields E × v/c. New to this incarnation are side-by-side atomic beam regions with common magnetic but opposite electric fields, and the addition of 23Na, with concomitant measurement equipment, to the atomic beams. The neighboring atomic beams provide common-mode noise rejection and an additional handle on some systematics. Simultaneous study of the sodium provides another handle, since it is insensitive to d e but susceptible to the same magnetic effects as thallium. Furthermore, sodium's two useful ground state hyperfine levels allow the separation of the two different types of motional field effects. The new result is d e = (6.8 ± 8.1) × 10−28 e cm. A detailed discussion of the experimental method is given. Several ancillary discoveries are also described, including a new kind of motional field systematic and a novel method for studying leakage/charging current effects, a general problem for experiments of this type. |
