Future Circular Collider beam screen: progress on Tl-1223 HTS coating

A Leveratto,A Moros,C Bernini,C Ferdeghini,J Bernardi,M Himmerlich,A Saba,M Putti,E Bellingeri,B Henrist,M Eisterer,S Calatroni,R Vaglio,S Holleis,S Fernandez-Peña

doi:10.1088/1361-6668/ab7fbd

Abstract

Thallium-1223, a superconductor with high critical temperature (Tc ∼ 120 K) and high irreversibility line is a promising alternative to copper layers as a low surface impedance material in particle accelerator components. In the existing design of the Future Circular Collider (FCC-hh), for reasons of cryogenic efficiency and vacuum stability, the beam screen that shields the dipoles from synchrotron radiation has to stay at best in the temperature range between 40 and 60 K, in which copper surface resistance might be too high to prevent beam instabilities due to wakefields. This paper reports the progress on the realization of thallium-1223 based high temperature superconducting (HTS) coatings realized by electrochemical deposition. The study of the Tl-1223 phase has been carried out on precursor-pellets and films. Transport characterization revealing a very high irreversibility line and also high local critical currents obtained from Scanning Hall Probe Microscopy (SHPM) measurements will be shown. A first analysis of compatibility in vacuum has been carried out and the generation of secondary electrons (SEY) has been investigated as well.The encouraging results, although not conclusive, will state that thallium-based phase could be suitable for the proposed application.

Highlights

A conceptual design for the generation of a circular collider at CERN (Future Circular Collider, FCC) was recently presented [1,2,3]
The coating with Tl-1223 has the peculiarity to be realized via electrochemical deposition [10, 11] thanks to the high out-of-stoichiometrytolerance with respect to RE-123
With energy dispersive x-ray spectroscopy (EDX) analysis, the different areas can be identified: on the top, we find the Pt protective layer, a thin layer of SiO, which stems from small contaminations in the fabrication process, and a large Tl-1223 grain on top of the STO substrate

Summary

Introduction

A conceptual design for the generation of a circular collider at CERN (Future Circular Collider, FCC) was recently presented [1,2,3]. The coating with Tl-1223 has the peculiarity to be realized via electrochemical deposition [10, 11] thanks to the high out-of-stoichiometrytolerance with respect to RE-123. It is a cheap and scalable technique, which could be considered for a direct deposition on tubes or arbitrarily shaped templates. Of coatings and precursor-bulks, useful for the film growth, by means of electrical resistance as a function of temperature and magnetic field, R(T, B), and scanning Hall probe microscopy (SHPM). Further the precursor-bulks are employed during the high temperature heat treatment

Sample preparation: bulk and film

Electrical transport and magnetization measurements

Vacuum and secondary electron yield behaviour

Conclusion