Electron Beam Characterization of REBCO-Coated Conductors at Cryogenic Conditions

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 (HTSs) 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 the XPS, SEM, and EDS methods. The energy and dose dependencies of ESD are comparable to those of technical-grade metals and one sample reached SEYMAX = 1.2 after electron conditioning.

Automated summary

Particle accelerators with superconducting magnets use a beam screen liner to extract heat and prevent it from reaching the magnets. The beam screen surface is typically made of high-conductivity copper and provides low impedance, low electron-cloud effect, and low dynamic pressure rise. High-temperature superconductors (HTSs), specifically REBCO-CCs, are being considered to decrease the beam screen impedance and allow operation at lower temperatures. Qualification of REBCO-CCs under accelerator-like conditions is necessary. The SEY and ESD of REBCO-CCs were measured at cryogenic temperatures, showing comparable energy and dose dependencies to technical-grade metals.