Instability modeling for passive harmonic-cavity operation at MAXlab

Abstract

Instability modeling is performed for passive harmonic-cavity operation at MAXlab. For the MAX-II 1.5 GeV ring, we consider the 100-MHz/500-MHz RF system now being constructed with three fundamental cavities and one harmonic cavity. We also model the existing 500-MHz/1500-MHz system on MAX-II. For the MAX-III 700 MeV ring, we model a 100-MHz/500-MHz RF system with one harmonic cavity, and a system with two identical harmonic cavities. For the proposed MAX-IV 1.5-GeV ring, we model a 100-MHz/500-MHz RF system with four fundamental cavities and one harmonic cavity. For the proposed MAX-IV 3-GeV ring, we model a 100-MHz/500-MHz RF system with ten fundamental cavities and two harmonic cavities. Instability plots are shown which predict the current range where optimal bunchlengthening by the harmonic cavity is stable. We note the calculated coupled-dipole Robinson frequency, at which a large amount of phase noise on the beam may be expected. In addition, the bunchlengths are calculated for the case without a harmonic cavity and for optimal bunchlengthening.