Narrow Results

A number of studies showed that the AC losses for B//c are much larger than that for B//ab due to the effects of I_c(B) behavior at 77K. We present the relation between AC losses and the orientations of DC magnetic field by a sample of Bi-2223 tapes with 37 filaments of a superconducting core, which were prepared by the powder-in-(Ag) tube (PIT). A universal formula on the relation between AC losses and the orientations of the DC magnetic field will be found out according to the ellipse model of the Norris equation. The formula will provide some useful hints for the theoretical analysis of AC losses.

This paper presents an investigation on ac losses of superconducting bulk caused by various magnetic wave conditions with the help of finite element software of Comsol Multiphysics. Three different magnetic wave conditions are analyzed, which are standing magnetic field, rotated magnetic field and traveling magnetic field. The calculation ac loss result was compared with that from analytical formulas for type-II superconducting slab and cylinder. The influences of the strength of external magnetic field on the ac losses were investigated. Effects of a relatively stable trapped-field of superconducting bulk on ac losses in time-varying magnetic field are clarified. Effect of spatially inhomogeneous distribution of the external magnetic field on the ac loss is studied.

We are focusing on the uncertainties of analytical and numerical analysis of AC losses in superconducting accelerator magnets working at a relatively high ramp rate. The loss experimental techniques are discussed as well as the source of error in the measurements. The correlation between the interstrand resistance of Rutherford cables and quench current behavior of superconducting magnets is addressed. The control of the critical current of full Rutherford cables by measuring the strands extracted from such cables is illustrated. The importance of cables curing temperature on microhardness and RRR of Cu-matrix of multifilamentary NbTi is pointed out.