Electron Beam Characterization of REBCO-Coated Conductors at Cryogenic Conditions

TL;DR

This study evaluates the secondary electron yield and electron-stimulated desorption of REBCO-coated superconducting tapes at cryogenic temperatures, assessing their suitability for use in accelerator beam screens to improve performance and reduce cryogenic load.

Contribution

It provides the first cryogenic SEY and ESD measurements of REBCO-coated conductors, including composition and morphology analysis, for accelerator applications.

Findings

SEY at 12 K can reach 1.2 after conditioning

ESD energy and dose dependencies are similar to metals

REBCO tapes show promise for cryogenic beam screen use

Abstract

Particle accelerators with superconducting magnets operating at cryogenic temperatures use a beam screen (BS) liner that extracts heat generated by the circulating bunched charge particle beam before it can reach the magnets. The BS surface, commonly made of high-conductivity copper, provides a low impedance for beam stability reasons, low secondary electron yield (SEY)to mitigate the electron-cloud (EC) effect, and low electron-stimulated desorption yield (ESD) to limit the dynamic pressure rise due to EC. Rare-earth barium copper oxide (REBCO) high-temperature superconductors (HTs) recently reached technical maturity, are produced as coated conductor tapes (REBCO-CCs), and will be considered for application in future colliders to decrease the BS impedance and enable operation at around 50 K, consequently relaxing the cryogenic requirements. Aside from HTS properties, industry-grade REBCO-CCs also need qualification for EC and dynamic vacuum compatibility under accelerator-like conditions. Hence, we report the SEY and ESD measured at cryogenic temperatures of 12 K under low-energy electron irradiation of 0 - 1.4 keV. We also verify the sample compositions and morphologies using XPS, SEM, and EDS methods. The energy and dose dependencies of ESD are comparable to those of technical-grade metals and one sample reached SEY$_{MAX}=$1.2 after electron conditioning.