A New High Resolution Optical System for Inspection of Gun – and Multi-Cell Resonators in ISO-4 Cleanrooms

Optical inspection of the inner surface of superconducting resonators was established during European XFEL cavity production by usage of the so called OBACHT optical inspection. In addition to the surface inspection by OBACHT a new optical inspection system with integrated high resolution camera is set up at DESY. It allows inspection of multi-cell resonators as well as gun resonators with only single side accessibility to the inner surface. A prototype was commissioned and optical inspections done with OBACHT and the new system in parallel. Two SRF gun cavities were inspected by this optical system and origin of limitations of the resonator were identified