Beam impedance mitigation for the FCC-hh would largely profit from superconducting coatings on the inner surface of the magnets’ beam screen. High-temperature superconductors (HTS) are the natural choice given the temperature (~60 K) and the external magnetic field (16 T) in which they should operate. Two approaches were devised in previous studies: (i) The use of coated conductors, which is an available HTS technology, but requires strategies to fix them on the beam screen. (ii) A cheap and scalable process of coating the beam screen with Tl-1223. Tl-1223 coatings on silver substrates have been demonstrated by electropolating, showing promising local properties. However, problems with phase purity and grain connectivity still have to be overcome.
It is planned to advance the technology of coating thallium-based HTS material (Tl-1223 / Tl-1212) on metallic substrates. The scope of this collaboration is to establish the correlation between the microstructure, the local superconducting properties and the resulting macroscopic performance of Tl-based superconducting coatings. This has been demonstrated to be very important for an effective optimization and will be achieved by a combination of micro- and nanostructural examinations (grain geometry, local texture, grain boundary morphology, compositional gradients) of the material structure and measurements of the superconducting properties by transport, magnetometry, and scanning probe experiments. The thus obtained insights will be an essential feedback for the Tl-based HTS coating development by CNR-SPIN.
USTEM will take care of detailed microstructural characterisation of Tl-1223 films prepared by electrodeposition and by alternative coating techniques. This includes high resolution chemical chracterisation by SEM-EDX, TEM-EDX and TEM-EELS (if required). An important task will be the structural characterisation of the textured film by electron diffraction and especially by EBSD. Due to the rather threedimensional surface structure of the films, new preparation routes will be explored in order to prepare suitable EBSD samples. The work will be performed by USTEM staff and a PostDoc.
The group at Atominstitut will mainly focus on SHPM complemented by SQUID measurements in order to assess the local and global properties of the coatings. Most of the work at Atominsitut will be done by a PostDoc.
The efforts to fix coated conductors to the beamscreen at ICMAB will be supported by scanning Hall probe measurements after the treatment to identify the reason of possible damage.
