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Figure 1
(a) Schematic spectrum of a FEL beam in two-color operation. The spectrum consists of two distinct spectral features at hν1 and hν2 and a spectral gap with a lack of intensity in between. For two-color experiments it is necessary to separate these features for the pump and probe beam. (b) Here hν2 is singled out in the grating beam path while hν1 is blocked. Panel (c) depicts the situation where hν1 is transmitted in the variable-delay path while hν2 is filtered out by an absorbing filter. |