Magnetic ejection of submilimeter-sized diamagnetic grains observed in a chamber-type drop shaft

Abstract

Abstract. Mass dependence of magnetically induced translation is examined for submilimetersized diamagnetic grain, which is floated in a diffused gas medium of 70 Pa by the use of microgravity μG condition. Here the grains are ejected from field-center of a pole-piece magnetic circuit by field-gradient force in a direction of decreasing field; maximum fieldintensity at initial point is about 0.6T. It was deduced from an energy conservation rule that magnetic potential of the grain at initial position was partially converted to kinetic energy during translation. Therefore, observed velocity was expected to be independent to mass of particle; this is because magnetic potential is proportional to mass of particle. In a given field distribution, the velocity was uniquely determined by intrinsic magnetic susceptibilityχ DIA of material. We report here that the magnetic ejection in μG condition is realized for sub-mm sized crystals of bismuth, graphite and magnesia. The χ DIA values obtained from the ejection agreed fairly well with the published values for the three materials. The mass-independent property of translation was examined by observing the translation of two bismuth grains with different sizes. A chamber-type drop shaft having a height of 1.5 m was introduced to produce the μG condition. By the use of this drop shaft, study of field-induced motion of a single diamagnetic particle becomes possible in an ordinary laboratory.

Magnetic ejection of diamagnetic sub-millimeter grains observed by a chamber-type μG generator orientated to identify material of a single particle

“…A line x = x R denotes the position where B = 0. The measured distribution of magnetic field along the x-axis is shown in the figure (Hisayoshi et al, 2011). Fig.…”

“…Of these, graphite has the largest published χ DIA , which is 5 × 10 −6 emu/g, whereas the published χ DIA of bismuth is 9.0 × 10 −7 emu/g, which is an order of magnitude smaller (Guputa, 1983). The data of graphite and bismuth observed in a previous report are listed in the table (Hisayoshi et al, 2011).…”

“…The compact magnetic circuit was assembled from a couple of Nd-Fe-B magnetic plates of size 2.5 cm × 2.0 cm × 0.6 cm. By adopting this magnetic circuit, a size reduction of the drop box became possible (Hisayoshi et al, 2011).…”

“…The samples were cut from a synthetic block having a purity of 99.99%. The χ DIA values of graphite-1 and bismuth-1 were measured in a previous study (Hisayoshi et al, 2011). …”