Abstract
Novel features of the longitudinal instability of a single electron bunch circulating in a low-emittance electron storage ring are discussed. Measurements and numerical simulations, performed both in time and frequency domain, show a non-monotonic increase of the electron beam energy spread as a function of single bunch current, characterized by the presence of local minima and maxima, where a local minimum of the energy spread is interpreted as a higher-order microwave instability threshold. It is also shown that thresholds related to the same zero-intensity bunch length depend linearly on the accelerating radio frequency voltage. The observed intensity-dependent features of the energy spread, confirmed by measurements with two independent diagnostics methods, i.e. horizontal beam profile measurements by a synchrotron light monitor and photon energy spectrum measurements of undulator radiation, are given a theoretical interpretation by applying a novel eigenvalue analysis based on the linearized Vlasov equation.
Highlights
Successful construction, commissioning and operation of several ultra-low emittance storage rings have had a decisive impact on the development direction of future synchrotron light source facilities
The energy spread is not changed by the collective effects if the beam intensity is low enough, but the longitudinal microwave instability occurs above a certain threshold current and results in the energy spread growth and in the beam brightness degradation
We study the onset of the microwave instability and its behavior well above the threshold current using precise measurements at the NSLS-II storage ring[11]
Summary
Low-intensity regime, the measured horizontal beam size depends upon the lattice functions βx and ηx and on the equilibrium values of the energy spread and emittance, the latter two of which are determined by the single-particle process of incoherent emission of synchrotron radiation. The measurements discussed in this paper, together with the methods used for their interpretation, offer an opportunity to predict and further characterize the microwave instability threshold, and represent an effort to enhance the understanding of the dynamic evolution of the energy spread above the threshold which may further enable controlled operation of electron storage rings at high current
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
