Detection of mixing ratio of binary-mixture particles based on a principle of magnetic separation conducted in a microgravity area

Translation of binary-mixture particles composed of solid CO2 and graphite were observed in an area of static magnetic-field that monotonically decreased in one direction, and magnetic susceptibility χmix of individual particle was determined from the observed relationship between translating velocity and field intensity. Using the variance of χmix value, mixing ratio f of graphite was speedily estimated without consuming the particle; here published χ values of solid CO2 and graphite were used in the estimation, and mass measurement of particle was unnecessary. In the experiment, the translated particles were quietly released in an area of microgravity produced by a short shaft with a height of 180 m (duration< 0.5 s), and the magnetic field was supplied by a pair of small Nd magnetic plate. The detection of f was based on a principle which realized magnetic separation of ordinary diamagnetic and paramagnetic particles at low field intensity. The experimental results confirm the efficiency of the energy conservation law proposed for the field-induced translation at a reduced temperature of T∼200 K. By improving the present apparatus, binary-mixture particles can be magnetically separated according to the sequence of their f value, and a histogram of f is speedily obtained from the population of separated particles. Such histogram will provide direct information to estimate the formation process of the binary-mixture particles, especially in various onsite missions on the terrestrial surface as well in the outer solar system.