| Abstract: |
In the field of superconducting radiofrequency (SRF) cavities for the acceleration of particle beams, commonly titanium-vessels are used to house cavities made from pure niobium whose intermediate space is filled with liquid helium to cool down the cavity to 2°K to reach superconductivity. The titanium-vessel is connected to piping for vacuum pumping, liquid helium transfer and the beam line, that are usually made from stainless steel. In former designs, the material transitions from titanium to stainless steel was realized by explosion bonding which restrict compact designs and are expensive to procure and fabricate. Brazed tubular transitions allow the application of thin-walled material and are more versatile with respect to design features. We brazed cylindric mechanical test samples and tubular transitions between pure titanium (Grade 2) and stainless steel AISI 316LN with AgCuIn- and AgGaPd-filler metals. Mechanical tests at room and cryogenic temperature with a posterior metallographic analysis of the brazed interface show satisfying shear strengths around 100 MPa at both temperatures. An extensive test campaign, including thermal cycling, non-destructive testing and metallographic analysis on different actual transition geometries were successfully conducted without degradation of the joints which qualifies these components for the use in particle accelerator technology.
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