Microwave Instability Beyond Threshold*

Stability of the Haissinski solution is studied above the threshold of microwave instability. It is shown that instability may lead to a new self-consistent state corresponding to particles trapped in a separat rix of an unstable mode. The free energies of the two solutions are compared. The relaxation oscillations between the new and Haissinski solutions are possible and may be related to the saw-tooth instability. Submitted to Physical Review E The microwave instability is one of a few problems of accelerator physics which is not fully understood today. The instability is usually described as an increase of the rms ener ~ spread of a bunch when NB, the number of particles per bunch, exceeds some threshold value. Because the equilibrium temperature is determined by th

Beam Diagnostic by Outside Beam Chamber Fields

Fields induced by a beam and penetrated outside the beam pipe can be used for a beam diagnostic. Wires placed in longitudinal slots in the outside wall of the beam pipe can work as a beam pickup. This has very small beam-coupling impedance and avoids complications of having a feed-through. The signal can be reasonably high at low frequencies. We calculate the beam-coupling impedance due to a long longitudinal slot in the resistive wall and the signal induced in a wire placed in such a slot and shielded by a thin screen from the beam. We present a field waveform at the outer side of a beam pipe, obtained as a result of calculations and measurements. Such kind of diagnostic can be used in storage rings, synchrotron light sources, and free electron lasers, like LINAC coherent light source

Study of Collective Beam Instabilities using a Correleation-moment Analysis

A general formalism for treating simultaneously the transverse coupled bunch and transverse coupled mode instabilities is presented. In this approach, the equations of motion of a coupled multi-bunch beam are expanded to yield a system of equations involving correlation-moments of the transverse and longitudinal motions. After a proper truncation, the system of equations is closed and can be solved. This approach allows us to formulate within one framework several known instability mechanisms including the single bunch mode coupling instability, the coupled bunch instability, the mode coupling instability, and the coupled mode coupled bunch instability as particular cases

Simulations of high disruption colliding beams

Recent B-factory proposals that use a linac beam colliding with the beam from a storage ring to achieve high luminosities (L > 10{sup 34} cm{sup {minus}2}sec{sup {minus}1}) result in very high disruption of the linac beam. The effects of such high disruption have been studied using the relativistic, 3-D code SWARM. We discuss the assumptions, parameters, and results of a series of runs that model such collisions. Regimes of high beam loss and methods to avoid them are also discussed. 5 refs., 4 figs