Method and apparatus for determining at least one characteristic of a superconductive film

Apparatus for measuring a characteristic of a film comprised of a material that is a superconductor below a critical temperature is described, comprising: means for maintaining the film at a temperature such that the film is in a superconducting state; means for inducing an alternating magnetic flux at a localized region of a surface of the film, said inducing means being responsive to a control input signal for varying a magnitude of the magnetic flux; and means, responsive to a current induced within the film by an entry of the magnetic flux into the film, for determining a critical current density of the film within the localized region