PROGRESS TOWARDS A MEASUREMENT OF THE ELECTRON ELECTRIC DIPOLE MOMENT USING COLD CS AND RB ATOMS IN A 1D OPTICAL TRAP
Open Access
- Author:
- Ebert, Matthew Fitzgerald
- Area of Honors:
- Physics
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- David Scott Weiss, Thesis Supervisor
David Scott Weiss, Thesis Supervisor
Dr. Richard Wallace Robinett, Thesis Honors Advisor - Keywords:
- Electron electric dipole moment
trapped neutral atoms - Abstract:
- In this thesis, we report progress towards a measurement of a permanent electric dipole moment (EDM) of cold Cesium and Rubidium atoms in a 1D optical lattice. A stable particle cannot have an EDM unless time-reversal and parity symmetry are violated. The Standard Model predicts an electron EDM of about 10^-38 e-cm, which is far smaller than the current experimental limit of 1.6 x 10^-27 e-cm. Much larger EDMs are predicted by proposed extensions to the Standard Model, such as Supersymmetry, Multi-Higgs and Left-Right symmetric models. Therefore, the detection of an EDM in the current experimental range would be the first direct observation of time-reversal symmetry breaking, and the first experimental observation of any kind that is inconsistent with the Standard Model. Laser cooling and trapping of atoms in precision measurements greatly reduces noise sources and increases the sensitivity of the experiment. Both Cesium and Rubidium are used, because laser trapping techniques for Cs and Rb atoms are well understood and because of the large EDM enhancement factors for each. The projected sensitivity of our experiment is 3 x 10^-30 e-cm, a 500-fold improvement over the current experimental limit and sensitive enough to test proposed extensions to the Standard Model. If a non-zero EDM is detected, the two species will provide a strong final check against systematic errors. The sensitivity of the experiment is determined by a few factors, one of which is magnetic field gradients, which in combination with an electric field gradient and imperfect electric field reversal can produce a false EDM signal. To reduce the magnetic gradient, two levels of cancellation coils and a magnetic shield will be implemented. Surrounding the experiment are six sets of background magnetic field cancellation coils that reduce the magnetic field to the mG range in order to prevent saturation of the shields due to the Earth's magnetic field. Surrounding the cavity where the atoms will be trapped is a passive shield constructed of mu-metal, which will decrease the magnetic field inside by a factor of at least 10^-4. Inside the shield there will be eight sets of magnetic coils designed to produce highly uniform magnetic bias fields and magnetic gradients. The spatial uniformity of the fields and field gradients are determined by the geometry of the coils, while the accuracy, precision, noise, and any time dependent effects are dictated by the power supply. The development and integration of a computer-controlled, low-noise, accurate power supply system for the coils will be discussed, as well as an introductory overview of the experiment and sources of error. An exhaustive description of the experiment is beyond the scope of this thesis.