Impedance measurement for various vacuum components in Pohang Light Source Storage ring

Abstract

The Pohang Light Source (PLS) is a 2 GeV, third-generation synchrotron light source which was recently commissioned. Loss factor measurements were carried out for various storage ring vacuum components using the synthetic pulse technique. The measurement was done for bunch lengths (sigma(l)) ranging from 7.1 to 30 mm. The measured devices were elliptical and circular photon masks, bellows with elliptical and circular cross sections, ellipse-to-diamond transition, ellipse-to-ellipse transition, beam position monitor chamber, and circular T-piece. Broad-band impedances were obtained by fitting the measured loss factors to broad-band resonator model. The total broad-band impedance of 250 devices was 0.17 Omega, which is a small fraction of the total machine impedance budget as expected in the calculation.