Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Influence of the Preparation Process on Microstructure, Critical Current
  Density and Tc of MgB2 Powder-In-Tube Wires   MgB2 wires and tapes suffer from a limitation of the transport current
densities, especially at low field, due to an unsufficient thermal
stabilization caused by hot spots from a non-homogeneous microstructure, the
presence of secondary phases and voids. For the preparation of MgB2 wires and
tapes two different precursor routes, using MgB2 (ex-situ process) or Mg + B
(in-situ process) are applied. The in-situ approach allows variation of many
parameters in the wire preparation and the improvement of this approach is the
central topic of this paper. We present an improved in-situ approach, the
characterization of the filament microstructure, effects from stoichiometry and
the corresponding superconducting properties. The transport current capability
of such in-situ wires could be improved to the level of the reference ex-situ
wires.

23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
3
The categories of this paper are: physics
9
The categories of this paper are: nlin