Generally when papers like this come out, there are a couple of decades' history behind them. (Disclaimer: I'm an experimental physicist, but don't have domain

Generally when papers like this come out, there are a couple of decades' history behind them. (Disclaimer: I'm an experimental physicist, but don't have domain knowledge in the subtleties of modern accelerator-cavity design, which is both an art and a science. Most modern accelerators, including LHC, are driven with superconducting niobium cavities.) Since essentially every author is at SLAC, I suspect that there is a strong cold-copper research group there. Can anyone with domain-knowledge summarize the generally-accepted strengths/weaknesses/risks of cold-copper accelerator designs?