Friday, 2C-13, 2:15-2:25

HTS Coated Cylinders Processed via Alternating Beam Assisted Deposition (ABAD)

A. Rutt

L. Kirchhoff¹, N. Freytag², A. Usoskin¹

¹Bruker HTS GmbH, Siemensstr. 88, 63755 Alzenau, Germany
Tel. +49 6023 500 637, Alexander.rutt@bruker-ehts.com
²Bruker Biospin AG, Industriestr. 26, 8117 Fällanden, Switzerland

HTS coated cylinders as a variant of coated conductors were always attractive because of lossless circumferential currents. Different application fields of coated cylinders as superconducting fault current limiter of inductive type, field gradiometers, NMR field formers have been listed earlier, and certain deposition techniques (as e.g. inclined substrate deposition) were developed to provide bi-axially textured buffer layer on cylindrical surfaces.

Here we report recent progress in manufacturing of bi-axially textured buffers on cylinders via ion beam technology. Ultimately, these buffered substrates should allow processing of HTS coated cylinders with small radius.

The bi-textured yttria stabilized zirconia (YSZ) layers on a cylindrical surface were manufactured by an alternating ion-beam assisted deposition technique where the film is periodically exposed to deposition pulses and to etching pulses. As a long sequence of alternations of these two pulses is needed, this method was called "alternating beam assisted deposition" (ABAD).

Two types of substrates were employed: a segment of the sapphire single crystal cylinder with diameter of 12 mm and length of 60 mm and a 100 µm thick stainless steel tape which simulated metallic cylinder of the same diameter.

Mechanically polished substrates exhibited a roughness of typically 6 nm. The thickness of the textured YSZ layer was 2.5 μm. The sapphire substrates were preliminary covered with an amorphous layer of chemically neutral material in order to prevent non-desirable orientations in YSZ film.

It was confirmed by XRD (θ-2θ and Φ-scan) that the YSZ [001] direction is normal to the substrate surface and the in-plane misalignment was better than FWHM=9 degrees for the both substrate types. These results were additionally confirmed by X-ray measurements of YBCO films deposited onto these bi-textured buffers.

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