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Determine whether a ring can hold microbunches of rms length below $\\sim 2 \\times 10^{-7}\\,\\mathrm{cm}$ in steady state, with quantum excitation, intrabeam scattering and laser phase noise included, giving coherent radiation at $1.35 \\times 10^{-6}\\,\\mathrm{cm}$ ($13.5\\,\\mathrm{nm}$) with average power near $10^{10}\\,\\mathrm{erg}/\\mathrm{s}$.","problem_ref":"d98cdaca290ac28b7ec854d5f47a9125d9fb4085c8bcc8ee300dc91c2ef4c18d","references":"","settled_by":"Measured steady-state coherent emission at the target wavelength whose power scales as the square of the number of electrons per microbunch.","status_note":"INSPIRE records through 2026 show proof-of-principle work at the Metrology Light Source and ring design studies, with no steady-state operation reported.","title":"Steady-state microbunching in a storage ring at EUV 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