Pretuning of 1.3 GHz 9-cell Ichiro copper cavity

A whole pretuning system was established and automatic measuring of the copper model of a 1.3 GHz 9-cell superconducting cavity was realized based on the commonly used theory of the tuning of multicell cavity’s field flatness. For the bead pull measurement of the field profile, a Labview program was written to acquire data and control the step motor cooperatively. A Java program was written to calculate the frequency correction of each cell by a series of matrix manipulation of the field profile data. Then one of the 9 cells was squeezed or stretched according to the estimated frequency correction. With the procedure repeated for several times, the multicell cavity was tuned to the design frequency and field flatness with good accuracy．