Water mist flow in a vertical bore of a superconducting magnet

The effect of magnetic field on water mist (diamagnetic) was investigated by both experimental and numerical methods. Water mist was produced by an ultrasonic atomizer and fed from the top of a cylinder that was located in a vertical bore of a superconducting magnet of 10 T or less. Water mist descends due to gravity at 0 T, but at 10 T it mostly levitates above the magnetic coil. In the numerical computation, water mist was simulated by 1000 water droplets 0.1-5 mu m in diameter d. Due to the small sizes of the water droplets, Brownian motion was considered and the Langevin equation was solved. At d < 1 mu m, the particles are driven by the Brownian motion extensively and the magnetic and gravitational forces have almost no effect on them. At d >= 1 mu m, the trajectories of particles are greatly deformed by the magnetic field when they go through the magnetic coil. At gamma(f)=1000 (10.8 T for 9 cm cylinder diameter), the bulk of the water mist took an hourglass shape above the coil just as observed experimentally. At gamma(f)=2000 (15.2 T), the water droplets were computed to be levitated against the gravitational acceleration.