1.3 GHz Cavity Weld to Helium Vessel

At DESY Hamburg superconducting accelerator units are under development for the FLASH and the XFEL Projects. (fig.1). Nine cell superconduction accelerator structures, also named cavities, with 1.3 GHz resonance frequency are made from Niobium sheet material by industrial partners. Those cavities are cooled by bath cooling with Helium at a temperature of 2K. For accelerator application each cavity is equipped with an individual helium vessel and is connected to a central feed in line and a gas return pipe of 300 mm