2017/05/09 by Shisong Li, Franck Bielsa, Michael Stock +4 · 3 citations
Decision Sciences · Engineering · Physics and Astronomy · #Advanced Electrical Measurement Techniques #Radioactive Decay and Measurement Techniques #Scientific Measurement and Uncertainty Evaluation
paper · doi:10.1088/1681-7575/aa71db
openalex publication_date 2017/05/09 · crossref created 2017/05/09 · crossref issued 2017/09/11 · crossref published 2017/09/11 · crossref published-online 2017/09/11 · crossref published-print 2017/10/01 · openalex created_date 2025/10/10 · crossref deposited 2026/06/27 · crossref indexed 2026/07/29 · openalex updated_date 2026/07/30
Abstract The magnet is one of the fundamental elements in Kibble balances. The Kibble balance group at the Bureau International des Poids et Mesures (BIPM) proposed a permanent magnet with a radial field, which has been widely employed in other Kibble balance experiments. In this paper, we discuss a different method of operation for the BIPM-type magnet, i.e. only the lower half of the magnetic circuit is closed. The merit of such a magnet is its convenience for opening the air gap and adjusting the coil. A disadvantage is that it can yield a lower and sloped magnetic field profile with less shielding. In the approach described, high permeability yokes are used to flatten the magnetic profile, which has proven to be a novel and convenient approach for removing the nonuniformity of the magnetic profile due to magnet magnetization asymmetries. The performance of the half-closed BIPM magnet is evaluated using experimental measurements. The results show that the half-closed magnetic circuit retains most of the main features of the fully-closed magnet and is a good option for the early stages of Kibble balance operations. In addition, the profile change due to the coil current is predicted and experimentally verified with a bifilar coil. Related systematic effects are discussed for the Planck constant measurement.