AbstractsPhysics

The demands to the FEL X-ray optics are extremely high. They must be able to preserve the properties of the new sources as good as possible; speaking not only of the enormous photon density per time, but also of coherence and extremely low divergence, generated by the FELs. This occurs at pulse repetition rates in the range of up to several kHz. Such high-energy pulses in the GW range pose the question of whether the used optics is able to withstand these conditions (for a longer time). Possible applications and limitations of modern optics such as reflection zone plates are investigated and demonstrated here. The present work involves both simulation and experimental tests. It is divided into four sub-projects. Each one describes the different states of the FEL. The first sub-project with the European XFEL GmbH in Hamburg includes the commissioning of the FEL. Here, two different methods for the precise adjustment of the undulator segments of the long FEL undulators (200 m) are presented, by measuring the so-called K-parameter, magnet field strength in the undulator, the product of magnet field and period length of a magnetic structure. For that, a 2- or 4-crystal monochromator is used, which is able to determine the K-parameters with an accuracy of 10-4 to 10-6. The proposed methods were successfully demonstrated using undulator radiation at the PETRA III facility. The second sub-project with European XFEL is dedicated to the measurement of the spectral parameters of the actual resulting FEL radiation from pulse to pulse, single-shot spectroscopy. For this purpose, various methods have been investigated that can register the spectral response with sufficiently high precision. It was thereby demonstrated that resolutions down to 3.2 meV at the pulse energy of 10 keV are feasible. In a third project, with LBNL in Berkeley and at LCLS in Stanford, a new spectroscopic setup was implemented, which is able to detect the fluorescence spectra from highly diluted elements under interaction of FEL X-ray pulses with a liquid jet in vacuum. The signals, previously not measurable due to low intensity in the complex context of photosynthesis spectroscopy were observed. The system development and a successful improvement are presented. The fourth project describes an X-ray transport line coupled with a spectrometer for conducting cross-dispersive resonant inelastic X-ray spectroscopy (RIXS) experiments. This is theoretically examined as a case-study. With this apparatus it is possible to achieve an energy resolution of E/DE ≈ 30,000 in the soft X-ray regime (776 eV as an example) at simultaneous recording of the absorbed and emitted radiation, which will enable a new class of fundamental research using RIXS experimental studies. Die Anforderungen an die FEL Röntgen-Optiken sind extrem hoch. So müssen sie in der Lage sein, die Eigenschaften der neuen Quellen bestmöglich zu erhalten. Dabei sprechen wir nicht nur von den enormen Photonendichten pro Zeit, sondern ebenso von Kohärenz und extrem geringer Divergenz, die FELs…