A cryogenic fluid level sensor utilizing a high temperature ceramic superconductor material driven above its level of critical current density, an exterior housing for holding the length of ceramic superconductor material, a support material disposed between the ceramic superconductor material and the exterior housing, and a resilient retention material disposed opposite the ceramic superconductor material for holding the superconductor material while allowing expansion and contraction thereof during thermal cycling. A method of producing a superconductor material having a low level of critical current density and favorable structural properties is also disclosed.