Correct Dumb-bells are very important to make sure the right field flatness,frequency of TM010 mode and length of 9-cell TESLA cavity.The shape of the dumb-bells will be wrong due to deep drawing,machining and EB welding.Then,the dumb-bells should be adjusted after iris and stiffness welding according to the mechanical and microwave measurement.Peking University has set up facilities for measuring and correcting the dumb-bells.This paper discusses the method of measuring and correcting the dumb-bells.
Researches on large grain superconducting cavities are carried out at SRF laboratory of Peking University. A 1.3GHz TESLA type single cell cavity and a 1.3GHz 2-cell cavity made of large grain niobium were fabricated by Peking University.With the collaboration of Jlab,the measured Eacc of the single-cell cavity reached 43.5MV/m after BCP,baking and high temperature heat treatment.
