G.P. Vedernikov

Cu-Nb and Cu/stainless steel winding materials for high field pulsed magnets

Two promising types of Cu/stainless steel (SS) macrocomposite and Cu-Nb microcomposite winding wires for large scaled high field pulsed magnets are reviewed. The estimation of the potentially achievable combinations of mechanical and electrophysical properties has been done. The features of corresponding manufacturing processes for Cu/SS and Cu-Nb wires are presented. The strength-conductivity properties of several types of Cu-Nb and Cu/SS conductors are given. Relationships between the microstructure parameters and mechanical properties of Cu-Nb wires are discussed. The RT (room temperature) ultimate tensile strength at the level of 900-1100 MPa and conductivity 50-60% IACS for Cu/SS conductors with cross-sections up to 40 mm/sup 2/ has been attained. For Cu-Nb wires with 6 mm/sup 2/ cross section the RT ultimate strength exceeding 1400 MPa has been attained.

Comparative study of AC superconducting strands and cables with copper-manganese and copper-nickel matrices

Comparative study was carried out on characteristics of model NbTi superconducting strands and (6+1) cables with copper-nickel (up to 29 wt.% nickel) and copper-manganese (up to 13.5 wt.% manganese) matrices. Hysteresis losses per cycle are presented for 0.2 mm strands at field amplitude from /spl plusmn/0.5 up to /spl plusmn/3 T. The contribution of own hysteresis of magnetization of copper-manganese matrix into integrated losses appreciably increases at fields above 1 T, while at fields below 1 T losses are comparable for both copper-nickel and copper-manganese strands. Losses at frequency up to 45 Hz and field amplitude up to 1 T for the CuMn cable without transport current are identical to those at slowly varying field. Rate dependencies of critical current in the cables are presented at linear build up of transport current. Critical currents in the CuMn cable at linear current building up and sweep rate exceeding that required for commercial frequency are not less than DC (/spl ges/260 A at 1 T).

Superconducting behaviour of Nb-Ti-12.3 wt.% Ta and Nb-Ti-20.4 wt.% Ta multifilamentary superconducting wires

Multifilamentary wires based on ternary Nb- Ti- Ta alloys with 55 and 4620 filaments have been fabricated by several processing routes. Ternary alloys with 12.4 and 20.4 wt. % Ta were used having Tc 8.99 and 8.70 K. Critical currents of the wires have been measured at 5–13.5 T and at 4.2 and 2.2 K. Critical current densities of the wires with 60–40 µm filaments and 7–3.5 µm filaments, which were prepared under the identical conditions, were compared for both the compositions.

An investigation of Nb-Ti-Ta alloys and properties of the superconductors based on ternary alloys

The vacuum arc melting technique was used to obtain the ingots of Nb-Ti-Ta alloys with 12.3 and 20.4 wt.% Ta. The microhomogeneity of the alloys was investigated by electron probe method and T/sub c/ of the alloys after homogenization was measured in comparison with that of the binary Nb-47.5wt%Ti alloy. Multifilamentary conductors with filament diameter /spl sim/60 /spl mu/m have been fabricated. The characteristics of the wires which have been produced by the regime with 4 intermediate heat treatments are presented.

Recent progress of low temperature superconducting materials at Bochvar Institute

Abstract According to requirements of the applications (fusion reactors, accelerators or superconducting switches), different NbTi and Nb 3 Sn strands have been developed and manufactured at Bochvar Institute (VNIINM) for several last years. Design of the fusion and accelerator strands is dependent on the required performance and function of the conductor to be used. Good performance superconducting persistent switches called for the use of high electrical resistivity matrix together with high current properties. The characteristics of the strands manufactured for toroidal (Nb 3 Sn) and poloidal (NbTi) field coils of experimental fusion reactor ITER are presented as well as the accelerator strands based on NbTiTa alloys and Nb 3 Sn and also the wires with CuNi and CuMn matrices for superconducting persistent current switches.

Development of fine filament NbTi superconducting strands for magnet systems of fusion reactors

Abstract Bochvar Institute (VNIINM) has developed and produced fine filament NbTi superconducting strands of several layouts for International Thermonuclear Experimental Reactor (ITER) poloidal field (PF) coils. The strands, having outer diameter of 0.7 mm and filament diameter of 6.5 μm, have been manufactured both by single and double stacking. Strand layouts distinguish by Cu/Sc ratio and a filament zone arrangement in cross-sections, one of them includes CuNi resistive barriers to reduce AC losses in operating condition of ITER magnet system. The results of comparative investigations on critical currents, critical current density, AC losses, critical temperature of the strands are presented. Two strands of these layouts are supposed to be used in the experimental cable for the model coil of SULTAN facility.

Trapezoidal Wire for the Hollow Superconducting Cable Designed for Fast Cycling Synchrotron Magnets

A new hollow high current cable was designed at JINR for the magnets of the GSI accelerator ring SIS 100. To increase both the structural current density and the operating current it was proposed to replace the superconducting wires with a round cross section (0.5 mm in diameter) by wires having a keystoned or trapezoidal (in the first approximation) cross section.Trapezoidal fine filament superconducting wire based on NbTi alloy, intended for operating at fields having sweep rate from 1 up to 4 T/s, has been developed and manufactured by Bochvar Institute (VNIINM). The wire with 10374 filaments and Cu/non Cu of 1.8 was fabricated by a single stacking method. Each filament was surrounded by a matrix of commercial MN‐5 alloy (Cu‐5wt.%Ni). The trapezoidal shape was formed by two steps drawing of a round 1.01 mm wire at a final stage of production. The optimized cross section is 0.73 × 1.08 mm at the medium line.The critical current density is more than 2700 A/mm2 at 5 T, 4.2 K. The current carrying capacity...

Superconducting properties of wires based on NbTi and NbTiTa alloys at 2 K and 4.2 K

Comparative investigations of superconducting properties at 4.2 and 2 Kelvin are presented for NbTi and NbTiTa wires manufactured by identical heat treatments. Three NbTiTa alloys with 12.4; 14.0 and 20.4 wt% Ta have been studied in this work. Single and double stacked wires with filament diameter from 20 to 3 /spl mu/m are under the consideration. An attempt to optimize critical current density for high field application is described.

NbTi superconductors designed for AC operation

Multifilament composite wire with submicron Nb-Ti filaments in Cu-Mn and Cu-Ni matrices are presented. Their current carrying capacity and electromagnetic losses in the conductors are given too. The prospects of the Cu-Mn alloys application instead of presently much used Cu-Ni ones as composite superconductor matrix materials are studied and discussed.

NbTi Billets for Superconductor Production

The distribution of microconcentrations of Ti in NbTi ingots, produced by various melting methods, are under the consideration. The surface gas saturations are investigated at recrystallization and homogenization heat treatments. The control measures, allowed to reveal billet defects in a process, are described. The 40 µm filament conductor, produced of NbTi billets, manufactured by VNIINM, has jc=3.2 × 105A/cm2and n = 87(5T;0.1 µV/cm).