Schmidt, B.; Wesch, S.: Echtzeitspektroskopie von Ferninfrarotstrahlung zur Strahldiagnose an Linearbeschleunigern Real-time far-infrared spectroscopy as diagnostic tool for linear accelerators. tm-Technisches Messen 81 (2014), p. 137–144

X-ray Free-Electron Lasers, driven by high-energy electron linear accelerators, require beam parameters beyond those of conventional machines. Of critical importance is the length of the accelerated electron packets („bunches“) which are compressed by special magnet sequences to well below 100 μm, resulting in peak currents of several kA. Monitoring and control of the longitudinal current distribution is one of the key challenges at these machines. Different phenomena lead to the emission of broad-band infrared radiation in the millimeter to micrometer regime whose intensity and spectral composition indirectly reveals the longitudinal current profile of the radiating bunches. During the past years, substantial progress has been made to develop powerful methods to measure and spectroscopically resolve this radiation in a way that on-line monitoring of the acceleration and compression process became possible.