Recently, we have developed efficient and practically shaped, epoch making high - Tc oxide superconducting wire in collaboration with the National Research Institute for Metals (NRIM) and Hitachi Ltd.

This new superconducting wire is called ROSAT wire (Rotation-Symmetric Arranged Tape - in - tube wire), and is either round shaped or rectangular shaped. Gnerally, high - Tc oxide superconducting material oxide-crystals have two types of crystal faces: one is electrically conductive and the other non-conductive. Because of this, in order to raise the wire's critical current density* it becomes necessary to arrange this 'electrically conductive face of crystal' in parallel and up to now if the high - Tc oxide superconducting wire was not tape shaped, the critical density could not be attained. However, now, we have in collaboration with the National Research Institute for Metals (NRIM) and Hitachi Ltd. through a completely new manufacturing method; applied all the advantages of a tape shaped wire to that of a round shaped wire structure and have successfully opened up new avenues for introducing practical uses for 1,000 A level high - Tc oxide superconducting wire.

One of the high - TC - oxide superconducting wires: the Bi (Bismuth) - 2212 wire has a far higher critical magnetic field at very low temperatures (liquid Helium temperature - 269 degree Centigrade), than metallic superconductors. Because of this it is considered possible to use it in a variety of equipment that applies high magnetic fields such as: nuclear fusion reactor, accelerators and medical treatment use MRI equipment etc., so it can be promoted much more energetically that past developments.

When the Bi - system superconductor is constructed in the way described above to raise the structure of the 'electrically conductive face of crystal' it is necessary to use the so called 'crystal alignment' parallel arrangement.
Furthermore, in order to obtain a critical current density, when the Bi - system superconductor's superconducting filaments are buried underground it becomes the case that smooth, silver areas of interface are increased. For the above reasons, in the past, Bi - system superconductors have been generally made of tape shaped wire using methods like those stated below:

1)	After filling up a silver pipe with superconducting materials powders, it is drawn and lengthened.
2)	Then it is rolled, and thin, dense multifilaments are formed.
3)	A heat treatment process for superconducting is carried out.

However, it is not easy to form uniform thickness or width with tape shaped wire like this, furthermore when making coils, because solenoid winding ** usually can not be done there is are big limitations on the production and the type of coil. It is hoped that the highly efficient round shaped wire that we have developed is able to overcome such obstacles as these.

The manufacturing method of the high - Tc oxide superconducting wire that we have just developed is: once the Bi - system multifilamentary tape-shaped wire is formed, the stacked tapes are put in the middle of a silver pipe again, then after drawing a heat treatment process for superconducting is carried out. Examples of this method have been tried before, but, after the tape has been put in and needs to be drawn there has been a problem whereby the shape of the filaments get easily distorted, and so this has become an obstacle to lengthening. In order to suppress this phenomenon, the tape shaped filament arrangement on the wire that we have just developed, has triple rotation symmetry in the inner section. Due to this, when processing, uniformity is achieved over the full width and distortion in the shaped section is almost completely banished.
By using technology, many homogenous tape shaped filaments can be buried inside the round shaped wire, the crystals inside the filament - 'the crystal alignment' is improved, also there are 1,000 filaments, increasing the amount from the previous tape shape by about 20 times, so meaning the silver areas of interface are also increased. The result of this is that the old shaped tape can bear no comparison, with a transport property of 1,000A as compared to 2,500A/mm2, and a critical current density was able to be realized for the first time (liquid Helium temperature - 269 degree Centigrade was measured).

Also at NRIM, the wire was measured in high magnetic fields (over 20 Tesla), proof that it has transport properties of over 300 A.
We expect to further push development in the future, for example next time for the high -Tc oxide superconducting wire we will use wire lengths in km units, and with the rectangular shaped wire develop magnets with homogeneous magnetic fields etc.
By removing the form limitations, that say that tape shaped wire must be used for high - Tc oxide superconducting wire, we hope to develop an even wider range of applications in the future.

* CRITICAL CURRENT DENSITY: Indicates a current flow position that can flow in a state of zero resistance to a superconductor.
** SOLENOID WINDING: The conductor is wound like thread round the same reel so is wound uniformly

INQUIRIES

Hitachi Cable, Ltd., Administration Dept., Legal & Corporate Communication Sec.,
Chiyoda Bldg, 1-2 Marunouchi 2-chome, Chiyoda Ku, Tokyo 100-8338
TEL: 03 - 5252 - 3261

National Research Institute for Metals,
2-1 Sengen 1-chome, Tsukuba, Ibaragi Prefecture 305-0047
TEL: 0298 - 59 - 2045

Hitachi Ltd., President's Office (Publicity Information),
6 Surugadai 4-chome, Kanda, Chiyoda Ku, Tokyo 101-8010
TEL: 03 - 3258 - 1111 (Dedicated Number)