Power losses in superconducting Nb in the presence of a.c. and d.c. magnetic fields and d.c. transport current

✍ Scribed by V.T. Kovachev; K.A. Nenkov; E.K. Nazarova; E.S. Vlakhov; M.G. Mikhailov

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 733 KB
• Volume: 25
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(85)90133-x

✦ Synopsis

Using an eleclronic warlmeler lechn,que Ihe power d,ssipalton in niobium under superposed a.c. and d.c. magnet,c helds and in the presence ol d.c. transport currenl has been investigaled. Diflerenl values of Ihe surface shielding I,eld depending on sample surface Irealment have been Iound. II has been eslabhshed Ihal chemical pohshmg pracllcally eliminales Ihe losses horn Ihe local penetration ol the magnellc Ilux ,nlo the sudace ,rregulartlles. It is shown Ihat Ioran a.c. held amplitude o1640 Acm -t the disstpated power m Ihe chemically polished n,ob=um is less by aboul two orders of magn,lude Ihan Ior samples wilh no surlace IrealmenL The observed disstpation minimum under superposed a.c. and d.c. magnellc helds ts expla,ned employing a model used earlier Ior Nb3Sn and Nb3Ge. The pecuhar,l,es ol Ihe c)q~/¢~t signal for n,obium compared wilh Ihat ol Ihe A15 compounds can be explained by Ihe relallvely high H,.t value ol niobium. The presence ol the transport currenl leads Io a 'displacemenr ol Ihe prohles ol the magnel=c IhJx penelralion mlo the superconduclor and Io Ihe 'hlhng' ol the observed mintmum.