Hoogerheide, Shannon Michelle Fogwell

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Hoogerheide, Shannon Michelle Fogwell

Hoogerheide

Shannon Michelle Fogwell

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Trapped Positrons for High-Precision Magnetic Moment Measurements
(2013-08-28) Hoogerheide, Shannon Michelle Fogwell; Gabrielse, Gerald; Manoharan, Vinothan; Silvera, Isaac
A single electron in a quantum cyclotron provides the most precise measurement of the electron magnetic moment, given in units of the Bohr magneton by g/2 = 1.001 159 652 180 73 (28) [0.28 ppt]. The most precise determination of the fine structure constant comes from combining this measurement with Standard Model theory, yielding \(\alpha^{-1} = 137.035 999 173 (34)\) [0.25 ppb], limited by the experimental uncertainty of the electron g-value. The most stringent test of CPT symmetry in leptons comes from comparing the electron and positron magnetic moments, limited by the positron uncertainty at 4.2 ppt. A new high-stability apparatus has been built and commissioned for improved measurements of the electron and positron magnetic moments, a greatly improved test of lepton CPT symmetry, and an improved determination of the fine structure constant. These new measurements require robust positron loading from a retractable radioactive source that is small enough to avoid compromising the high-precision environment of our experiment. The design and implementation of such a scheme is a central focus of this work. Robust positron loading at a rate of \(1-2 e^+/min\) from a \(6.5 \mu Ci^{22}Na\) source has been demonstrated.