A fast switching mirror unit at FLASH

Abstract The F ree Electron Las er at H amburg ( FLASH ) facility at the D eutsches E lektronen- Sy nchrotron (DESY) is a linear accelerator that is operated in superconducting technology and produces soft X-ray laser light from 4.5 to 47 nm. Several switching mirrors, located in the experimental hall, provide different beam lines with laser light, where the switching procedure lasts up to 1 h and is performed at intervals of days or sometimes weeks. Since the experiments would be sufficient even with a lower repetition rate of the beam, a new kind of switching mirror has been invented. In this paper, the design and implementation of a fast switching mirror at FLASH are presented where focussed and unfocussed beam trains can be distributed between two beam lines with a frequency of up to 2.5 Hz. The challenge lies in the precise repetition accuracy of position (few μm) and angle (about 1 arcsec) of the mirror. In addition, first measurements taken at FLASH are analyzed and they show only little influence of the developed switching mirror on the beam position.