Absolute Magnetometry with 3He: Cross Calibration with Protons in Water

The muon magnetic moment anomaly a_mu is a measure of how the g-factor of the muon differs from the Dirac equation value of 2. Contributions to a_mu from the Standard Model (SM) arise from QED, strong, and electroweak interactions. The current 3.3 sigma discrepancy (~2.5 ppm) between the measured value of a_mu and the SM prediction could be a strong signal of BSM (beyond Standard Model) physics. This experimental value was measured at Brookhaven National Lab (BNL) with an uncertainty of 0.54 ppm. The measurement relied on absolute calibration of the magnetic field, which was measured with a system of proton NMR probes through a calibration chain referenced to an absolute probe with pure water. The uncertainty of the absolute calibration was quoted as 50 ppb due mainly to temperature dependent effects, perturbations due to materials, and the diagmagnetic shielding factor. In this dissertation work, we cross-calibrate both BNL absolute calibration probes with an independent magnetometer based on hyperpolarized 3He gas and perform pulsed NMR on the samples for frequency extraction, which is proportional to the magnetic field. Studies in both low fields (~0.003 Tesla) and high fields (1.45 Tesla) are reported. The cross-calibration campaign and corrections made to measure the field to the water and 3He standards are described. The results of the cross-calibrations are 0.92 +/- 2.23 Hz for the cylindrical BNL probe and 1.24 +/- 2.29 Hz for the spherical probe with ~37 ppb uncertainty for each. The ~2.3 Hz error for both is dominated by uncertainties from systematic corrections and 37 ppb is with respect to proton NMR frequency in 1.45 T.PhDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/151468/1/midhatf_1.pd