New densimeter for cryogenic fluids by magnetic levitation of a high‐T_c superconductor Available to Purchase

A new magnetic densimeter for cryogenic fluids has been developed by adapting a magnetic levitation of a high‐T_c superconductor. In this instrument, a superconducting material made of Y–Ba–Cu–O is sealed in a hollow glass buoy, and a stable levitation of the buoy is carried out with the Meissner effect of the superconductor simply by placing the buoy in the fluid above a ring‐shaped permanent magnet. The fluid density is obtained from the magnetic force required to levitate the buoy in the fluid. To measure this force, the magnet is suspended from an electronic balance and the reaction force acting on the magnet is determined directly as a change of the apparent weight of the magnet. Details are given of the theoretical calculation of the force acting on the superconductor in the magnetic field and of the construction of the apparatus. The measurements of the saturated liquid density of nitrogen have shown a standard deviation of 0.014%. The total uncertainty of the measurements is estimated to be less than 0.06%. The results agree with reliable literature values within the experimental uncertainty.