Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High transport critical currents in dense, metal-clad superconductor
  wires of MgB2   In this letter, we report the first successful fabrication of dense,
metal-clad MgB2 superconductor wires as well as the first demonstration of high
transport Jc of greater than 36,000 A/cm2 in MgB2. The fabrication technique
that we devised uses only ambient pressure, yet produces very dense MgB2 with
little loss of stoichiometry. Such a technique can be useful for rapid and
reliable compound syntheses and characterizations for future discovery of new
or improved superconductors with higher Tc, higher Hc2 or improved flux pinning
characteristics. We also show that while inherently weak-link-free, the nature
of the material is such that the grain boundaries of the polycrystalline MgB2
can easily be altered to exhibit induced weak-link behavior with accompanying
loss in critical current density by orders of magnitude.

36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin