4th July 2014: Prof. Eric Hellstrom’s invited lecture at ICMAB.

Prof. Eric Hellstrom from the Applied Superconductivity Center at National High Magnetic Field Laboratory (USA) was invited to the ICMAB and he lectured about “Development of Bi-2212 wires for High-Field Magnet applications”.

Short abstract: Bi-2212 (Bi2Sr2CaCu2Ox) is the only cuprate-based high-temperature superconductor (HTS) that can be made as a round wire.  These round wires can be made with a multifilament architecture, can be twisted, and can be easily cabled (Rutherford and 6-on-1 cables), which are important attributes for building high-field magnets (> 30 T).

Even though the first round-wire Bi-2212 were made in 1989, until recently, Bi-2212 wires did not have high enough J_c for practical applications.  The problem was bubbles that form in the wire during processing that block current.  In this talk I will describe the development of overpressure (OP) processing, which is a form of hot isostatic pressing (HIP), that removes the bubbles and yields high J_c.  Now that we have identified and can remove the main current limiting mechanism, we are reinvestigating all aspects of the heat treatment of Bi-2212 to understand how each portion of the heat treatment affects the final electromagnetic properties of Bi-2212.

http://www.magnet.fsu.edu/search/personnel/getprofile.aspx?lname=Hellstrom&fname=Eric