  The superconducting properties of copper-sheathed MgB2 wires fabricated by
conventional powder-in-tube techniques and the in-situ reaction procedure are
analysed. The influence of the processing conditions and initial (1+x)Mg + 2B
(x = 0, 0.1, 0.2) proportions of the precursors on the critical current values
of the wires have been studied. In particular, the limits of the available
temperatures and times for heat treatments imposed by the chemical reaction
between Mg and Cu, and their effect on the superconducting properties of the
wires, are discussed. The analysis includes the study of the sample
microstructure and phase composition as well as of the critical current
temperature and field dependences. The wires show high thermal stability during
direct transport measurements and carry a critical current density of 1.3x109
A/m2 at 15 K in the self-field for optimised processing conditions.
