The impedance database and its application to the APS storage ring

Abstract

Since the operation of the APS storage ring, we have observed instabilities of different kinds. Some of them are not well understood and need further investigation; transverse saw-tooth instability and anomalous energy spread are examples. Quantitative understanding of these instabilities requires detailed knowledge of impedance of the ring. For this purpose we developed the concept of the impedance database, where the wake potential of each vacuum component in the ring is deposited and maintained in a standard form. These standardized wake-potentials can be manipulated with high flexibility by utilizing the Self Describing Data Sets (SDDS) toolkit developed at Argonne National Laboratory. In this paper we will present the total impedance of the APS storage ring obtained by using the impedance database. Then we report the application of the total impedance to investigate the currently observed instabilities in the APS storage ring.