High field superconductor development and understanding

Larbalestier, David C.¹  Lee, Peter J.¹  Tarantini, Chiara¹ 

[1]Florida State Univ., Tallahassee, FL (United States)

关键词: Superconductors;    Superconducting wire;    Nb3Sn;    REBCO;    Bi-2212;    critical current density;    critical temperature;    heat treatment;    image analysis;   

DOI  :  10.2172/1158690
RP-ID  :  DOE-FSU--FG02-07ER41451-Final
PID  :  OSTI ID: 1158690

美国|英语

来源: SciTech Connect

【 摘 要 】

All present circular accelerators use superconducting magnets to bend and to focus the particle beams. The most powerful of these machines is the large hadron collider (LHC) at CERN. The main ring dipole magnets of the LHC are made from Nb-Ti but, as the machine is upgraded to higher luminosity, more powerful magnets made of Nb₃Sn will be required. Our work addresses how to make the Nb₃Sn conductors more effective and more suitable for use in the LHC. The most important property of the superconducting conductor used for an accelerator magnet is that it must have very high critical current density, the property that allows the generation of high magnetic fields in small spaces. Nb₃Sn is the original high field superconductor, the material which was discovered in 1960 to allow a high current density in the field of about 9 T. For the high luminosity upgrade of the LHC, much higher current densities in fields of about 12 Tesla will be required. The critical value of the current density is of order 2600 A/mm² in a field of 12 Tesla. But there are very important secondary factors that complicate the attainment of this critical current density. The first is that the effective filament diameter must be no larger than about 40 ??m. The second factor is that 50% of the cross-section of the Nb₃Sn conductor that is pure copper must be protected from any poisoning by any Sn leakage through the diffusion barrier that protects the package of niobium and tin from which the Nb₃Sn is formed by a high temperature reaction. These three, somewhat conflicting requirements, mean that optimization of the conductor is complex. The work described in this contract report addresses these conflicting requirements. They show that very sophisticated characterizations can uncover the way to satisfy all 3 requirements and they also suggest that the ultimate optimization of Nb₃Sn is still not yet in sight