Susceptibility of Diamagnetic Particles Measured in a Microgravity Using a Simple Double-Capsule System

Abstract

Attempts to improve the accuracy in detecting diamagnetic susceptibility DIA of a small particle are conducted by measuring its magnetic translation. In this study, accuracy improvement was pursued by two different experiments. First, translation of particle was observed under micro-gravity () condition produced by a facile double capsule system that was developed to sufficiently reduce the residual-gravity (residual-). In particular, gravity () was reduced to a value below 210-3 for 0.5s by selecting the optimum material of the outer capsule. Furthermore, a facile technique to produce a time lag between the drop of the inner capsule considering the outer capsule was effective in minimizing the initial -vibration of the inner capsule. Preliminary experiments using this double-capsule system indicated that the typical error of DIA was reduced by a factor of 5 (i.e., DIA~210-7 emu/g) when compared to that obtained in a previous study under condition. Many phenomena studied in condensed matter physics are completed within a short time scale below 0.1s, and the new system is still effective if the complete insulation of the sample from the measuring device is required, as realized in the DIA measurements experiment reported in this paper. In another experiment, horizontal parabolic translation was conducted in normal gravity; here translation was induced by a field-gradient force produced by a Nd magnetic circuit. The accuracy of DIA obtained by field-induced translation was significantly improved, by optimizing the field distribution of the magnetic circuit; typical error of DIA remained at a level of 510-7 emu/g. Compared to the aforementioned double-capsule system, the compact apparatus operated in normal- can be easily transported to various sites of material exploration to conduct preliminary DIA measurement of the test samples, therefore improving the efficiency of material exploration.