Transverse Impedance Measurement in SuperKEKB

In KEK(Japan), SuperKEKB project is progressing toward upgrade. This project aims improvement luminosity (8×10³⁵ cm⁻²s- 1) which is 40 times of the performance of the KEKB accelerator. In Phase 1 of this project, a performance test as storage ring was carried out. Understanding of ring Impedance/wake is an important subject in phase I. Measurement of Head Tail Damping using Turn by Turn monitor was performed to evaluate impedance/wake. Betatron motion is excited by kicker and its damping is measured for several parameters sets of bunch current and chromaticity in both HER and LER. The wake field was calculated from the decrement of betatron amplitude. We present the wake field which is cross-checked with tune shift based on the current dependence.