# Trapped Positrons for High-Precision Magnetic Moment Measurements

 Title: Trapped Positrons for High-Precision Magnetic Moment Measurements Author: Hoogerheide, Shannon Michelle Fogwell Citation: Hoogerheide, Shannon Michelle Fogwell. 2013. Trapped Positrons for High-Precision Magnetic Moment Measurements. Doctoral dissertation, Harvard University. Full Text & Related Files: Hoogerheide_gsas.harvard_0084L_11015.pdf (60.95Mb; PDF) Abstract: 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. Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10985007 Downloads of this work: