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Figure 6
Measured spectra of the fundamental harmonic (a) and the third harmonic (b) resonant lights at a wavelength of ∼1530 nm in a single-bunch operation. The FEL oscillations were on (solid lines) and off (dotted lines) the threshold at an electron beam current of ∼1.0 mA in (a) and 1.6 mA in (b). The undulator gaps were 103 mm (K = 3.03) in (a) and 71.5 mm (K = 5.60) in (b). The dispersive gaps were 135 mm in (a) and 108 mm in (b). |