The fabrication method where a duplex alloy is mechanically reduced to wires or tapes by simple metallurgical processes, that is rolling, swaging and wire-drawing after ingot-casting is an approach for producing composite materials. The composite produced by this method is called the in situ formed composite. This process was first applied to the production of superconducting materials by Tsuei and thereafter many works have been carried out extensively. This in situ formed superconducting composite has following characteristics. (1) Aligned superconducting filaments are fine but discontinuous. (2) The strength of composites is relatively high. (3) The superconducting properties, especially Jc, are stable against stress. The recent improvement of the fabrication method enables to produce the in situ formed composites with a large volume fraction of Nb3Sn filaments. Such composites show good superconducting properties with an overall Jc of 106A/cm2 at 4.2K and O field, which is comparable to that of the commercial Nb3Sn composite. Although the possible mechanisms of superconductivity in the in situ formed superconducting composite are considered to be filament effect, proximity effect and the direct contact of superconducting filaments, the latter two mechanisms will become important with increment of the volume fraction of superconducting filaments. More work remains to be done in improving Jc at high field and the stress effect of Jc.
In September 1978, production of liquid hydrogen was started on industrial scale (730l/hr) in our country in order to meet the increasing demand for the space development field. Nowadays, Japan has occupied a position comparable with Europe for supplying liquid hydrogen in commercial base. In this paper, the actual state of LH2 storage and transportation systems is introduced, and especially our experiences for LH2 transportation are described.