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Title Performance of Seamless Cavities and Fabrication Experience.
Type Talk  
Abstract Performance of seamless cavities produced by hydroforming or spinning is analyzed and compared with conventionally manufactured EB welded cavities. RRR degradation and grain growth in welding areas of conventional cavities can be critical for the performance. Good progress of last years in the welded technology allows overcoming most problems on the way towards high gradient. RRR degradation in welding area can be avoided by combination of careful preparation for welding, improved vacuum conditions and cavity post purification; magnetic field enhancement on the grain boundaries of the welding area can be avoided by electropolishing. The highest achieved accelerating gradient is up to now the same for both versions (ca. 40 MV/m.)  Nevertheless seamless cavity fabrication is desirable in order to overcome the welding risk and get reliable statistics. Moreover comparison of available data for both types of cavities after sufficient BCP treatment shows better performance of seamless cavities. Technological problems of the fabrication of seam less cavities are mainly solved thanks to the progress in fabrication of seam less tubes and parameter optimization. There is an indication that the material properties potentially can be improved by pressurization during hydroforming.  Fabrication of seamless cavities from bimetallic NbCu tubes deserves more attention. On the one hand it allows reducing the niobium costs; on the other hand it increases the thermal stability of the cavity. The highest accelerating gradient achieved on seamless bimetallic single cell cavity is Eacc = 40 MV/m. This is far better result in comparison with performances known for NbCu sputtered cavities.

List of authors...

Principle author first.

Last (Family) Name First Name (Initials only) Affiliation or Organization (abbreviations if possible)
Singer Waldemar DESY



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