High-Accuracy Absolute Magnetometry with Application to the Fermilab Muon $g-2$ Experiment

TL;DR

This paper introduces a high-precision absolute scalar magnetometer based on pulsed proton NMR, capable of measuring magnetic fields with 19 ppb accuracy, and demonstrates its application in calibrating other magnetometers and in the Fermilab muon g-2 experiment.

Contribution

The paper details the design, testing, and correction procedures for a novel absolute scalar magnetometer using proton NMR, achieving high accuracy for fundamental physics measurements.

Findings

Achieved 19 parts per billion accuracy in magnetic field measurement.

Successfully calibrated other NMR magnetometers.

Applied the magnetometer in the Fermilab muon g-2 experiment.

Abstract

We present details of a high-accuracy absolute scalar magnetometer based on pulsed proton NMR. The $B$-field magnitude is determined from the precession frequency of proton spins in a cylindrical sample of water after accounting for field perturbations from probe materials, sample shape, and other corrections. Features of the design, testing procedures, and corrections necessary for qualification as an absolute scalar magnetometer are described. The device was tested at $B = 1.45$\,T but can be modified for a range exceeding 1--3\,T. The magnetometer was used to calibrate other NMR magnetometers and measure absolute magnetic field magnitudes to an accuracy of 19 parts per billion as part of a measurement of the muon magnetic moment anomaly at Fermilab.