Immo Bahns

• European X-Ray Free-Electron Laser

Bragg reflectors are essential for beam transport in X-ray free-electron laser (XFEL) facilities. On interaction with Bragg reflectors, a part of the pulse energy will be absorbed, causing the propagation of displacement waves due to rapid thermal expansion. It is suspected that these waves may cause stability problems for XFELs operating with mega...

In this article, the concept of a recently funded R&D project for the installation of a proof-of-concept cavity-based x-ray free electron laser (CBXFEL) demonstrator experiment at the European XFEL facility is presented, with the first results expected in 2024. It is composed of an x-ray cavity design in backscattering geometry with a 133 m round t...

Modern X-ray free-electron laser (XFEL) sources can deliver photon pulses with millijoule pulse energies and megahertz repetition rate. As shown by the simulations in this work, for particular cases the dynamical heat load effects for Bragg reflectors could cause problems at these facilities. These problems would be underestimated if only quasi-sta...

An X-ray free-electron laser oscillator (XFELO) is a fourth generation X-ray source promising radiation with full three dimensional coherence, nearly constant pulse to pulse stability and more than an order of magnitude higher peak brilliance compared to SASE FELs. Proposed by Kim et al. in 2008[1] an XFELO follows the concept of circulating the li...

The interaction of an X-ray free electron laser (XFEL)with a Bragg Reflector can cause a change of the lattice constant, which has a direct influence on the stability of the reflection conditions and can also excite modes of vibration. The dynamical thermoelastic effects of the photon-matter-interaction are simulated with a finite-element-method (F...

This work presents an optical pump-probe setup for measuring the thermal evolution of diamond crystals at cryogenic temperatures under the heat load conditions of an X-ray free-electron laser oscillator (XFELO). As an XFELO is based on a cavity using diamond Bragg reflectors and these reflectors are subjected to intense heat loads during operation,...