Studies On Magnetic System Of Joule Balance As A Quantum Mass Standard

The unit of mass, kilogram, is one of seven base unit in the International System of Units. However it is the last one defined as a material artifact standard: IPK (international prototype kilogram). The direction of modern metrology progresses towards quantum standard on the basis of fundamental physical constants substituting for material artifact standard. Nowadays the explorations of redefinition of unit of mass are all prepared for connecting the mass unit to fundamental physical constants in the work of redefinition international unit system. Especially it is trend to define the unit of mass in terms of Plank constant h.This paper analyzes comprehensively the fashionable quantum mass standard: Watt balance, and introduces Joule balance that lately was paid more attentions. A kind of axisymmetrical coils system with novel dimension scale was presented. The theoretical calculation and experiment results showed that the homogeneous magnetic field generated by this kind of axisymmetrical coils system was satisfied with the requirement of accurate measurement of structural parameter: mutual inductance M.This research focused on magnetic circumstance which ensured the accurate measurement of structural parameter: mutual inductance M, which was pioneer work of magnetic system of Joule balance. The abundant effective work was achieved in this research.1. A kind of axisymmetrical coils system with novel dimension scale was presented. Through analysis and numerical calculations, it proved that annular homogeneous magnetic field whose axial length was 2cm existed near the symmetrical plane of magnetic system of Joule balance. The conditions were that the distance between inner and outer of exciting coils R and the distance between exciting coils and suspended coil H was satisfied with R2=4/3H2 , and the number of turns of inner and outer of exciting coils and suspended coil was satisfied with 10000:2700:430. Mutual inductance M had forth order homogeneity in annular homogeneous magnetic field.2. The parameters of magnetostatic field of magnetic system of Joule balance were calculated by analytic functions, including magnetic density, mutual inductance of Joule balance in annular homogeneous magnetic field and Lorentz force of suspended coil.3. The distribution of magnetic field of Joule balance was simulated in terms of finite element simulation software ANSYS, which could verify dimension of annular homogeneous magnetic field. According to the characteristics of magnetic vector potential of axisymmetrical coils, the several calculation procedures based on LabVIEW were compiled, which were applied to calculate parameters of magnetostatic field. The elliptic function was calculated by numerical integration. The parameters of magnetostatic field were obtained as possible as accurately and quickly, for instance magnetic induction intensity, magnetic gradient, mutual inductance, mutual inductance gradient, applied force between coils and so on. It had proved that calculation procedures had universality and expandability.4. The magnetic system of Joule balance was elaborated, including exciting coils and suspended coil. After assembling and aligning exciting coils system, the distribution of magnetic field was measured through localization system and Tesla meter, which proved the existence of annular homogeneous magnetic field. The measured value matched to theoretical calculation value, where the maximal difference was less than lowed to 4‰.