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WEA01PO04
Superconducting Properties of Sn Added RHQT-Nb3Al
Wires through the Clad-Chip Extrusion Method
S. Saito, N. Kodaira, Y. Kikuchi, T. Iijima, S. Takeuchi, S.
Nimori, Ishikaga Institute of Technology.
Fabrication and superconducting properties of Sn added
Nb3Al wires are presented. The adopted process consists
of the clad-chip extrusion (CCE) method and the rapidheating,
quenching and transformation (RHQT) treatment.
The former (CCE) is characterized by the extrusion of thin
chips of Nb/Al clad-rolled sheet and can produce the Sn
added Nb/Al composite precursor wire with the intended
chemical composition. The latter (RHQT) is a heattreatment
method to transform the precursor wire into A15
intermetallic compound of Nb3Al. It can produce not only
the nearly stoicheometric composition but also fine grain of
Nb3Al, which are favorable for upgrading the
superconducting properties. The combined process of CCE
and RHQT successfully fabricated several kinds of Snadded
Nb3Al wires with Sn-concentration from 1.25 at% to
5at%. Sn-addition affected the RHQT treatment condition
to transform to A15 phase from the precursor wire. The
BCC supersaturated solid solution became unstable just
after the RHQ-treatment and A15-phase became
predominant with increasing Sn-addition. The RHQTtreated
Nb3Al wire with nearly 2 at% Sn showed the
maximum Tc. The Sn-addtion to the RHQT-Nb3Al wire
enhanced the critical field of Bc2 (4.2K) though they
showed decreasing Jc at lower magnetic fields than 20T
comparing with binary Nb3Al wires.
WEA01PO05
Strain and Temperature Dependence of Nb3Sn Strands
in Critical Current
S. Oh, J. Kim, C. Lee, K.W. Cho, K. Kim, Korea Basic
Science Institute; P-Y. Park, Kiswire Advanced
Technology.
A through understanding of the superconducting properties
of Nb3Sn strands to strain is important for the proper
performance prediction of large superconducting fusion
magnets where the strands are used in large multi-strand
cable-in-conduit conductors at high magnetic field. A
variable-temperature WASP(Walter Spring) probe is
developed for the critical current density measurement of
Nb3Sn strands as a function of strain, field and
temperature. Both the compressive and tensile strain can
be applied up to 0.7 % while the temperature varies from
4.2 K to 16 K under the magnetic field up to 16 T. Several
types of internal tin Nb3Sn strands (Jc > 900 A/mm2 at 12
T and 4.2 K) optimized for the ITER TF(Toroidal Field) coils
are investigated for the comparative study on the axial
strain and temperature dependence of the critical current.
WEA01PO06
Critical Current of Nb3Sn Strands under Axial and
Transverse Stress
S. Oh, J. Kim, C. Lee, K. Kim, Korea Basic Science
Institute.
In Nb3Sn cable-in-conduit conductors for large scale
superconducting magnet applications, an axial stress is
applied to the strand by the thermal contraction difference
between the jacket material and the stand. During the high
field operation, there is an additional transverse stress in
the cable due to Lorentz force. In order to investigate the
effect of the stress by two major causes, a new device is
developed which can apply both the axial and transverse
stress. The axial strain can be applied reversibly from -0.7
to 0.7 % to the strand soldered on a C-shape ring and the
compressive transverse force is applied up to 4 kN. A
preliminary result on the combined effect of axial and
transverse stress on the critical current of Nb3Sn strands
optimized for the ITER TF(Toroidal Field) coils is
presented.
WEA01PO07
High field performance of bronze-processed Nb3Sn
near Bc2
H. Kurahashi, K. Itoh, S. Matsumoto, T. Kiyoshi, NIMS; Y.
Muramaki, H. Yasunaka, JASTEC; H. Wada, University of
Tokyo; T. Miyazaki, Kobe Steel, Ltd.
The multifilamentary Nb3Sn superconductors made by the
so called bronze process are now commercially available
and a 930 MHz (=21.9T) high field NMR magnet wound by
this type of Nb3Sn conductor was recently successfully
manufactured. Meanwhile, there has been growing
recognition that superconductors with high field
performance are needed to manufacture high field magnets
over 22 T. To improve the high field performance of Nb3Sn
conductors, the addition of one or more third elements to
the bronze matrix and/or Nb-core is well known to be quite
effective. Previously, we have measured the upper critical
magnetic field of bronze-processed Nb3Sn with and
without the addition of various third-elements to the bronze
matrix. In this study, we have investigated the effect of
each element, reaction temperature and critical magnetic
field on the critical current. The results will be discussed
based on metallurgical observations by XRD, SEM, and
EPMA.
WEA01PO08
Prebending strain effect on CuNb/Nb3Sn
superconducting wire during practical react-and-wind
process
G. Nishijima, H. Oguro, S. Awaji, K. Watanabe, Institute for
Materials Research, Tohoku University; K. Katagiri, Iwate
University; K. Miyoshi, S-I. Meguro, The Furukawa Electric,
Co., Ltd.
Prebending strain effect is that the repeated bending load
at room temperature enhances superconducting properties
of practical Nb3Sn wires. The authors are now focusing the
application of the effect to practical superconducting coils
fabricated by the react-and-wind method. The 1.0-mm
diameter CuNb/Nb3Sn wire, which was heat-treated at 670
C for 96 hours, was insulated with polyimide tape
wrapping. The insulated wire was pulled into the pulleys for
the prebending process. The wire was repeatedly bent by
using 10 pulleys. Prebending strain values were controlled
by changing the pulley diameters; 100 mm for 1.0 %
prebending, 125 mm for 0.8 % prebending, 200 mm for 0.5
% prebending, respectively. Finally, the prebent wire was
wound on a 200 mm diameter stainless steel bobbin. To
investigate the superconducting and mechanical
properties, short samples were picked out in each process;
after the heat treatment (HT), after the insulation wrapping
(IW), and after the prebending process (PP). Magnetic field
dependence of critical current (Ic) was measured at 4.2 K
in the fields up to 25 T. Tensile stress/strain dependence of
Ic was also measured at 4.2 K in 14 T. The measured Ic
was 154 A, 183 A, 204 A for the samples HT, IW, and
PP(1.0% prebending), respectively. The slope of the
stress-strain curve for the sample PP was steeper than that
for the sample HT, implying the effect of work hardening
caused by the repeated prebending strains.
89 MT-19 2005, Genova