Design of the Tsinghua Tabletop Kibble Balance

The Kibble balance is a precision instrument for realizing the mass unit, the kilogram, in the new international system of units (SI). In recent years, an important trend for Kibble balance experiments is to go tabletop, in which the instrument’s size is notably reduced while retaining a measurement accuracy of <inline-formula> <tex-math notation="LaTeX">$10^{-8}$ </tex-math></inline-formula>. In this article, we report a new design of a tabletop Kibble balance to be built at Tsinghua University. The Tsinghua Kibble balance aims to deliver a compact instrument for robust mass calibrations from 10 g to 1 kg with a targeted measurement accuracy of <inline-formula> <tex-math notation="LaTeX">$50 \mu \text{g}$ </tex-math></inline-formula> or less. Some major features of the Tsinghua Kibble balance system, including the design of a new magnet, one-mode measurement scheme, the spring-compensated magnet moving mechanism, and magnetic shielding considerations, are discussed.