“…comes from the preceding undulator sections or is induced by the bunching b n with the calibrated coefficients c n ≈ {1, 1.3, 2, 5, 10}, d n ≈ {1, 3, 8, 40, 120}. Theoretical results for so calibrated saturated harmonic powers (5) and their evolution (7) were carefully matched also with the numerical simulations [25] and describe the available data for all major FELs in [7,8]. Second harmonic oscillations in an optical cavity, such as in [26], are not covered by the proposed formalism.…”