Performance of the monochromator beamline at FLASH

The performance of the high-resolution monochromator at FLASH, the vacuum ultra-violet free-electron laser at DESY in Hamburg, was investigated. Using different techniques we measured the relative and absolute transmission of the monochromator beamline for FLASH radiation in the fundamental and higher (up to third) harmonics. The focal spot size of the soft x-ray beam at the output of the beamline was determined as well. In addition, a new way of acquiring the resolving power of the monochromator is discussed. This method has also been applied to calibrate the energy scale of the monochromator system with an accuracy of 5 meV at 48 eV photon energy.