Software Assessment of Accelerator Structure Quality with Bead-pull Technique

Software program to evaluate the quality of traveling-wave accelerator structure at Argonne National Laboratory was developed. In order to understand the extent to which the structure was tuned and thus determine the amount of tuning required, local reflection coefficient Γn of each cell in the structure must be measured. The program acquires the perturbed and unperturbed global reflection coefficients, S11p and S11u, with a network analyzer and uses the data to compute Γn based on Steele's perturbation theory. We verified the accuracy of the software program by testing on a pre-tuned 42-regular-cell accelerator structure operating at 2π/3 mode. The results give us cell-to-cell phase advance error of less than 0.5 0 , and the absolute value of the average local reflection coefficient is better than the standard value in the literature.