An ultra-precise determination of the mass of helium-3 using Penning trap mass spectrometry

The atomic mass of 3He has been measured using a Penning trap mass spectrometer. Measurements were carried out by observing the axial mode frequency shifts of a single ion due to excitation of the cyclotron mode in an ultra-stable 6.0 T magnetic field. Coupling between the axial and cyclotron modes is effected by introducing a small anhaxmonic term in the potential, or, alternately, by introducing a small magnetic perturbation. The leading systematic in the experiment is due to image charges in the trap electrodes interacting with the single ion, contributing a shift of 226(10) ppt. Other systematics include a kind of "light shift" associated with the axial drive energy being weakly coupled to the radial cyclotron mode, and a shift associated with setting the phase, which can distort the axial lineshape. A systematic associated with an inconsistency of the least-squares fit of the cyclotron resonance at different sweep ranges is also present. Ultimate resolution of the spectrometer is limited by the non-linearity of the magnetic field drift (<5 ppt) over hundreds of hours of observation. The new value for the atomic mass of 3He is 3 016 029 321.250(360). This represents a factor of three improvement over the previously accepted value, and a full order of magnitude improvement over the recent measurement. The excellent agreement with the most recent value affirms the conjecture that a hidden systematic shifted the value of the previously accepted result.;Details of the physcial spectrometer, particle loading and contaminant removal, and simulation work involving the range/fit systematic are given with detailed explanations. Early work on a future external ion-loading system is also presented.