Electron Cloud at High Beam Currents

The density and the wake elds of the e-cloud are quite dierent at low and high beam currents. The wake elds are derived and applied to the upgraded PEP-II B-factory.

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 instability and microbunching due to coherent synchrotron radiation

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 synchrotron radiation of the bunch is usually suppressed by the shielding effect of the conducting walls of the vacuum chamber. However an initial density fluctuation with a characteristic length much shorter than the bunch length can radiate coherently. If the radiation reaction force results in the growth of the initial fluctuation, one can expect an instability which leads to microbunching of the beam and an increased coherent radiation at short wavelengths. Such an instability is studied theoretically in this paper

On the Symmetry of the Impedance

The reciprocity theorem is used to prove the symmetry of the longitudinal impedance of an accelerating structure with respect to exchange of the coordinates of the leading and trailing particles. (2 refs)

Plasma Possibilties in the NLC

Basic idea and preliminary analysis are presented of a possibility to compensate the energy spread and to collimate beam in the next generation of linear colliders (NLC) using tunneling ionization of a gas by the beam