After a brief introduction to the problem, I study several aspects related to the horizontal instability in the KEKB HER, namely resistive-wall instability, ion trapping and ion instability, ion losses and the associated modification of the fast beam-ion instability, measurements of coupledbunch oscillations and their simulation assuming they are driven by ions, resistive wall, or electron clou...

Initial operating experience with the SLAC electron-positron storage ring SPEAR is described. A single-beam coherent instability, which can be suppressed either by control of the ring chromaticity or by feedback, has been observed. A second single-beam coherent instability has been observed at currents around 50 mA and is not yet understood. Current-dependent bunch lengthening and widening have...

Multi-bunch instabilities degrade beam quality through increased beam emittance, energy spread and even beam loss. Feedback systems are used to suppress multi-bunch instabilities associated with the resistive wall of the beam ducts, cavity-like structures, and trapped ions. A new digital transverse bunch-by-bunch feedback system has recently been commissioned at the Taiwan Light Source, and has...

KEK-ATF is studying low emittance, multi-bunch electron beam for the future linear collider. The energy instability of the 1.5 GeV linac has been a problem making the beam injection to the damping ring unstable. Because the unstable beam generates also large amount of the radiation, the beam current is limited by the KEK radiation safety policy much lower than what we expect. Stabilizing the S-...

We present a comprehensive study of the one-dimensional modulation instability of partially spatially incoherent light in noninstantaneous self-focusing media. For this instability to occur, the nonlinearity has to exceed a specific threshold that depends on the coherence properties of the beam. Above this threshold a uniform-intensity partially spatially coherent wave front becomes unstable an...

To reach high peak currents driving Free-Electron Lasers an initial chirped electron bunch is compressed in a bunch compressor. The interaction of the electron beam with its radiation field can yield a collective instability, which amplifies any initial modulation in the current profile. We present a model, which allows one to derive an explicit analytical expression for the gain of the microbu...

A relativistic electron beam moving in a circular orbit in free space can radiate coherently if the wavelength of the synchrotron radiation exceeds the length of the bunch. In accelerators coherent radiation of the bunch is usually suppressed by the screening effect of the conducting walls of the vacuum chamber [1, 2]. The screening effect is weak for short wavelengths, but if the wavelength is...

A strong, fast, transverse instability has long been observed at the Los Alamos Proton Storage Ring (PSR) where it is a limiting factor on peak intensity. Most of the available evidence, based on measurements of the unstable proton beam motion, is consistent with an electron-proton two-stream instability. The need for higher beam intensity at PSR [1] and for future highintensity, proton drivers...