Click here to download the abstract booklet in pdf format - MT19 - Infn

adiation resistance to the J-PARC grade. These
modifications will be completed by the end of March 2006.
Then approximately 80 radiation resistant magnets will be
prepared for the J-PARC 50GeV-PS. We have reported our
R&D works on polyimide-insulation and MIC magnets in
the previous MT conferences. At the coming MT-19, we will
report the status of the mass production/preparation of
these radiation resistant magnets for the actual
construction of the J-PARC.
POSTER SESSION 13:30 – 15:30
MgB2
MOA01PO01
Stability considerations of MgB2 superconductor
A. Stenvall, A. Korpela, R. Mikkonen, Tampere University
of Technology / Institute of Electromagnetics.
Magnesium diboride, MgB2 is a tempting superconducting
material in real technical applications due to its relatively
simple structure and high critical temperature. It is widely
believed that the MgB2 conductors could deliver the wire
performance required for applications operating at 20-30 K
in the $1 to $3 per kA-m range in the near future. The
material is suitable especially at low field dc applications
such in MRI devices and induction heaters. The stability
analysis of MgB2 is however challenging. This is due to the
fact that most conductors include ferromagnetic
constituents in matrix metal. In addition the electromagnetic
behaviour can be either isotopic or anisotropic depending
on the conductor configuration. In this paper the numerical
stability model is presented both for an individual MgB2
multifilamentary conductor and also for model solenoid.
The results are compared to equivalent LTS and HTS
magnets.
MOA01PO02
Bending Introduced Strain Effects on the In-situ
Fabricated MgB2 Wire with Fe Sheath
X. Li, L. Xiao, Z. Zhang Institute of Electrical Engineering,
CAS.
The effects of bending on Jc and Tc of MgB2/Fe monocore
wire fabricated via in-situ PIT method were
investigated. With the decreasing of the bending radii, Jc
and Tc decrease significantly. The cracks in the
superconductor were suggested to be the main reason of
such degradation. The critical parameters of the bended
wire were able to recover after post-annealing.
MOA01PO03
Fabrication of 130m-class MgB2/Fe/Cu wires and the
results of small coil tests
H. Kitaguchi, K. Tanaka, H. Kumakura, NIMS; H. Yamada,
M. Hirakawa, Central Japan Railway Co.; M. Okada, HRL,
Hitachi Ltd.
We made 130m-long Fe/Cu-composite sheathed MgB2(Mg
+ amorphous B) wires through PIT route. The diameter of
the wires is 0.8mm. Two small solenoid coils were
fabricated using different batches of the wires and using
wind & react process (heat treatment at 873-923 K for 1-10
h.) The test results of a coil using a 58m-long piece (459
turns) have been reported so far. In this paper, we report
the test results of the other coil made of 86m-long piece
(642 turns) and the comparison between these two coils. In
the coil tests, we measured Ic of the coil under various
external fields and temperatures. The Ic of the coil reached
195 A (engineering current density, Je, =390 A/mm2) at 4.2
K and in the external field of 1 T. The coil generated 1.95 T
(the center magnetic field, Bo), thus the total field reached
2.95 T. Je exceeded 100 A/mm2 in the external fields
below 3.5 T, 2.5 T, and 1.5 T at 15 K, 20 K, and 25 K,
respectively. These performances of 86m-coil are similar
very much to those of 58m-coil. This indicates that the
fabrication process of 130m-long wire and the heat
treatment process are highly reproducible.
MOA01PO04
Self-field Loss in AC Transport Current for Ni-sheathed
MgB2 Superconducting Tapes
S. Murase, M. Iino, S. Kim, N. Nanato, Okayama
University; Y. Yamada, K. Tachikawa, Tokai University.
AC transport current loss (self field loss) of exsituprocessed
MgB2 superconducting tapes with Ni sheath
was measured under different conditions of transport
current value, transport current frequency, and
temperature. Experimental results were compared with
Norris’ theoretical curve, which were larger than the
theoretical one and decreased with increasing frequency.
Furthermore, loss – normalized transport current (transport
current normalized by critical current) curves varied with
temperature and the loss at 9 K was larger than that at 14
K. The frequency dependency of the loss is considered to
be due to the skin effect. Although one of the loss origins is
the hysteresis of ferromagnetic nickel-sheath, the
hysteresis loss of Ni was to be negligibly small based on
the estimation and measurement for loss of Ni. Main
contributions to large loss are clarified by introducing a
model of three concentric layers of MgB2 core in the wire
caused by the inhomogeneity of critical current density and
critical temperature. The measured curves and
characteristics of loss – normalized transport current
accorded with the calculated curves using above
mentioned three-layered model.
MOA01PO05
Superconducting properties of MgB2 tapes fabricated
with different alloys as sheath materials
V. Braccini, C. Fanciulli, M. Tropeano, M. Vignolo, A.
Tumino, A. Malagoli, C. Bernini, G. Grasso, A.S. Siri,
INFM-LAMIA.
At present, MgB2 appears suitable for niche applications at
low and intermediate magnetic fields, and it has been
shown to possess magnetic field capabilities that can be
improved so as to overcome those of the best low Tc
superconductors at 4.2K. At the same time, viable wire and
tape technologies have been developed leading to samples
with good superconducting properties over long lengths.
We studied the influence of the deformation process, the
sheath material and the precursor powders on the
superconducting properties of ex-situ powder-in-tube
processed MgB2 tapes. We used magnetic (Ni), slightly
magnetic (Ni-W alloys) or non-magnetic (Ni-Cr alloys)
sheaths. We used a commercially available Ni80-Cr20
alloy and we produced Ni-Cr and Ni-W alloys with different
Cr or W percentages. We correlated their structural and
physical properties with the different chemical
compositions. Being these Ni alloys much harder than the
Ni, their use induces a higher degree of stress improving
properties such as the critical current density and the
irreversibility field. On the other side, it is very hard to be
cold-worked and cracks may occur in the phase,
deteriorating the properties of the superconductor. We
studied the influence of the pre-reacted MgB2 powders on
the final properties of the tapes. We used powders with
different granulometry, and doped in a different way, in
order to increase the critical current density and improve
the magnetic field capability of such tapes.
MT-19 2005, Genova 24