Collective temperature anisotropy instabilities in intense charged particle beams

The classical electrostatic Harris instability and the electromagnetic Weibel instability, both driven by a large temperature anisotropy (T∥b T⊥b 1) that develops naturally in accelerators, are generalized to the case of a one-component intense charged particle beam with anisotropic temperature, including the important effects of finite transverse geometry and beam space-charge. Such instabilities may lead to an increase in the longitudinal velocity spread, which makes focusing the beam difficult, and may impose a limit on the beam luminosity and the minimum spot size achievable in focusing experiments. This paper describes recent advances in the theory and simulation of collective instabilities in intense charged particle beams caused by large temperature anisotropy. The new simulation tools that have been developed to study these instabilities are also described. Results of the investigations that identify the instability growth rates, levels of saturations, and conditions for quiescent beam propagation are also discussed.