Measurement of critical current for bulk superconductors by transport method

✍ Scribed by T.S. Kikegawa; H. Sasaki; H. Tada; T. Kudo; H. Kikuchi; K. Konno; M. Muralidhar; M. Murakami; K. Noto; S. Awaji; K. Watanabe

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 134 KB
• Volume: 426-431
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2005.02.099

✦ Synopsis

The method of critical current measurement in a magnetic field using a DC transport current has been developed for bulk superconductors. The measurement of the critical current, I c , up to 50 A at a temperature of 77 K became possible by reducing thermal and mechanical stresses caused in the sample due to rapid cooling from the room temperature to 77 K and a electromagnetic force (Lorentz force), etc. The critical current of 50 A is reduced into 14,000 A/cm 2 of critical current density, J c , with a cross section of 0.0035 cm 2 . The magnetic field dependence of J c was investigated from 1 T to 10 T for (Nd 0.33 Eu 0.38 Gd 0.28 )Ba 2 Cu 3 O y bulk superconductors. The magnetization measurement was performed for the sample cut out from the same part of the same crystal as that used for the transport measurement of I c , from which the critical current density was also estimated. In low magnetic fields, the magnitude of critical current density obtained by the transport method, J T c , was larger than that estimated from the magnetization, J M c . This result reflects the difference of criterion to determine the value of J T c and J M c . In higher magnetic fields, however, it was observed that J T c was smaller than J M c and the irreversibility field estimated from J T c -B curve is slightly lower than that given by the magnetic hysteresis. When the external magnetic field was applied, anomalous voltage peaks in the I-V curve were observed below I T c , which may be caused by the sample slightly moving by the Lorentz force.