Impedance Analysis of Longitudinal Bunch Shape Measurements at PLS

We measured the longitudinal bunch shape by a streak camera at 2.5 GeV Pohang Light Source (PLS). The impedances estimated by a series R+L model indicate a resistance R=0.96 kΩ, an inductance L=80 nH and a longitudinal impedance | Z/n|eff= 0.53 Ω . The scaling law for the bunch lengthening is expressed as I^0.22. The effects of insertion device in the ring on the impedance, particularly the effect of the vertical height of the in-vacuum undulator currently placed in the PLS ring is also presented.