1,649 research outputs found
Fabrication and transport critical currents of multifilamentary MgB2/Fe wires and tapes
Multifilamentary MgB2/Fe wires and tapes with high transport critical current
densities have been fabricated using a straightforward powder-in-tube (PIT)
process. After annealing, we measured transport jc values up to 1.1 * 105 A/cm2
at 4.2 K and in a field of 2 T in a MgB2/Fe square wire with 7 filaments
fabricated by two-axial rolling, and up to 5 * 104 A/cm2 at 4.2 K in 1 T in a
MgB2/Fe tape with 7 filaments. For higher currents these multifilamentary wires
and tapes quenched due to insufficient thermal stability of filaments. Both the
processing routes and deformation methods were found to be important factors
for fabricating multifilamentary MgB2 wires and tapes with high transport jc
values.Comment: 13 pages, 7 figure
Scaling Behavior of Quasi-One-Dimensional Vortex Avalanches in Superconducting Films
Scaling behaviour of dynamically driven vortex avalanches in superconducting
YBaCuO films deposited on tilted crystalline
substrates has been observed using quantitative magneto-optical imaging. Two
films with different tilt angles are characterized by the probability
distributions of avalanche size in terms of the number of moving vortices. It
is found in both samples that these distributions follow power-laws over up to
three decades, and have exponents ranging between 1.0 and 1.4. The
distributions also show clear finite-size scaling, when the system size is
defined by the depth of the flux penetration front -- a signature of
self-organized criticality. A scaling relation between the avalanche size
exponent and the fractal dimension, previously derived theoretically from
conservation of the number of magnetic vortices in the stationary state and
shown in numerical simulations, is here shown to be satisfied also
experimentally.Comment: 7 pages, 5 figure
Investigating properties of heavy and superheavy atomic systems with configurations
We have investigated energies and spectroscopic properties such as lifetimes,
factors, and hyperfine structure constants of the neutral atoms P through
Mc belonging to Group-15, singly ionized atoms S through Lv of Group-16
and doubly ionized atoms Cl through Ts of Group-17 of the
periodic table. These elements have configurations with , which
are highly open-shell and expected to exhibit strong electron correlation
effects. We have used four-component Dirac-Coulomb Hamiltonian along with Gaunt
term and a relativistic effective core potential through the relativistic
multi-reference configuration interaction method to perform the calculations
with sufficient accuracy and compare the results with the available literature
data. These comparisons suggest that our predicted values, for which
experimental data are not available, are reliable enough to be useful for
future applications.Comment: 19 pages,12 table
On the sample size dependence of the critical current density in MgB superconductors
Sample size dependent critical current density has been observed in magnesium
diboride superconductors. At high fields, larger samples provide higher
critical current densities, while at low fields, larger samples give rise to
lower critical current densities. The explanation for this surprising result is
proposed in this study based on the electric field generated in the
superconductors. The dependence of the current density on the sample size has
been derived as a power law ( is the factor
characterizing curve ). This dependence provides one with
a new method to derive the factor and can also be used to determine the
dependence of the activation energy on the current density.Comment: Revtex, 4 pages, 5 figure
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