Seismic noise analysis and isolation concepts for the ALPS II experiment at DESY

Abstract

The ALPS II experiment at DESY is searching for new particles beyond the standard model of particle physics in a laboratory-based Light-Shining-through-a-Wall experi- ment, using high finesse optical resonators to reach the required sensitivity. The input and output mirrors on the optical tables have extremely accurate positioning and align- ment requirements, for which the analysis of ground vibration and seismic noise is essen- tial. This thesis, therefore, focuses on this analysis, its evaluation, and the development of future seismic isolations for the ALPS II and JURA experiments. This work describes mechanical vibrations, seismic noise sources, seismic isolation principles, and also the seismic devices used to perform seismic noise analysis with their methods of measuring, calibrating, and analysing the acquired data. It summarises the seismic noise studies carried out in the ALPS II laboratories at HERA West as well as in the hall and tunnels of HERA North at DESY in Hamburg. For a more accurate presentation of the prevailing noise frequencies a new method of the modal analysis, the MfwaFFT was developed. Here, a noise-independent procedure for more precise data analysis is implemented which accounts for the highly sensitive conditions on-site. Furthermore, a seismic isolation concept based on this analysis in connection with the ALPS II experiment is developed and presented.