METHOD AND APPARATUS FOR MEASURING MAGNETICAL CRITICAL CURRENT OF SUPERCONDUCTOR, AND METHOD AND APPARATUS FOR MEASURING TRANSITION TEMPERATURE

摘要

PURPOSE:To shorten a measuring time and to reduce the load in the temp. control of a sample, by constituting the detector of a combination of SQUID, a magnetism detection element of a magnetoresistant element or Hall element and a differentiator. CONSTITUTION:A pair of pickup coils 3, 3 wound in mutually reverse directions are connected in series and a ring-shaped superconductor sample 6 is arranged so as to surround one coil 3. An external coil 5 is arranged so as to surround the coils 3 and the sample 6 in almost coaxial relation to the coils 3. A magnetic field changing timewise is generated by the coil 5 and a superconductive current shielding the internal region of the ring of the sample 6 and developing along with the changing magnetic field is generated in the specimen 6 and the critical current value of the specimen 6 is correlationally measured from the magnitude of the magnetic field generated by the coil 5 when the voltage of the coil 3 when reaching the critical current value of the specimen 6 becomes almost zero. Therefore, since a pulse magnetic field can be utilized, a short-time measurement can be performed and the temp. control load of the sample is reduced.