Longitudinal Impedance Tuner Using High Permeability Material

We have succeeded in canceling longitudinal space charge effects using the 'impedance tuner' at the KEK-PS. The impedance tuner consists of the new material, 'FINEMET' which has large permeability over the beam spectrum region. A frequency shift of coherent quadrupole mode is measured to infer the modified impedance. It turns out that nonlinearity unavoidable in a longitudinal RF bucket has to be treated carefully in order to digest observed beam signals. We describe how to measure the impedance from the beam signal, how to analyze the effect of impedance tuner, and how to succeed in canceling space charge effects.