Connecting Superconductors by Laser Irradiation III

Abstract

Production of oxide superconductors requires heat treatment which limits size of maximum superconductive area depending on the capacity of the electric furnace. A study on connecting superconductors was conducted to obtain large area superconductors such as for magnetic shield. A combination of two pieces of same superconductors with a pasted medium of the identical phase powder at their joint portion were installed on a jig system settled on an X-Y table to be exposed to laser irradiation. Two kinds of Bi system samples i.e., one is 2212 phase thick film prepared on MgO substrate and one is 2223 phase sintered bulk were used as starting materials respectively. A CO₂ laser beam accompanied by oxygen gas blow was irradiated onto the medium along the contact line at the fixed defocus distance of 120mm under the conditions: laser output power 180-500W, assist gas pressure 98-194kPa, beam scan speed 2-10mm/min and beam scan times 4-7strokes. The laser irradiation onto the 2223 phase medium was conducted both top and bottom surfaces. As a result, Tc_(end) of 60.6K and 77.3K was obtained for 2212 phase and 2223 respectively after laser irradiation.