Longitudinal impedance tuner using high permeability material

Abstract

We have succeeded in canceling longitudinal space charge effects using the 'impedance tuner' [7] 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 will 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.

Multi-harmonic acceleration with high gradient MA cavity at HIMAC

“…However, if the beam emittance occupies the large area of the rf bucket, then the measured synchrotron frequency tends to deviate from Eq. (4) and become smaller value [5]. On the other hand, the synchrotron frequency at large amplitude of the synchrotron motion is as same that at small one for the saw-tooth rf.…”

RF parameter curves for a proton driver synchrotron

“…The idea is not new; [4] it has been tried in two different machines. [5,6] However, studies have not been carried out over a wide range of beam energy, momentum spread, etc., and more are needed.…”