Electron bunch time pattern of FLASH with 10 Hz repetition rate and up to 500 bunches in an 500-μs-long bunch train. The separation of electron bunches within a train is 1 μs. To a certain extent, the bunch distance in a train can be varied; for instance to 2, 5, or 10 μs and some other distances. The duration of the electron bunches is 20 to 300 fs. The nonlinear FEL process reduces the duration of the photon pulses down to 10 - 200 fs.
