⁶He-CRES: The mapping and error analysis of the superconducting magnet field

The ⁶He-CRES collaboration at the University of Washington CENPA aims to measure the Fierz-interference coefficient from the beta decay of ⁶He with high precision in the pursuit of finding signatures of new physics. The experiment uses cyclotron radiation emission spectroscopy (CRES) of the beta particles trapped inside a waveguide by a magnetic field. A superconducting solenoid surrounding the waveguide generates a magnetic field that can be shimmed to improve uniformity. An NMR probe with a rotatory mount is deployed to measure the magnetic field non-uniformity around the inner bore. From the measurements of the unshimmed field, the magnet can be adjusted to have better uniformity. The probe mount is improved with a spring locking system and vernier scale to decrease the propagated error. The final error analysis shows an error of approximately 1 ppm from the probe measurement. This result lowers the possible systematic errors for further measurements.