Shot-to-shot wavelength characterization of high repetition free-electron laser pulses

This thesis presents the setup and the results of the commissioning and measurements of a grating spectrometer in combination with the GOTTHARD detector. For the first time, shot-to-shot wavelength spectra at high pulse repetition frequencies of the multi-bunch mode of the free-electron laser (FEL) FLASH were recorded. The wavelength spectra were used to compensate the shot-to-shot wavelength fluctuation of the FEL pulses in simultaneously taken photoemission spectra of atomic neon. The selection according to the mean pulse wavelengths results in a significant reduction in the photoemission peak widths equivalent to a respective improvement in resolution of the photoemission spectra. Furthermore, the shot-to-shot wavelength spectroscopy enables detailed FEL machine studies and systematic investigations of space charge effects in the multi-bunch mode at FLASH as demonstrated in this thesis.