TRANSVERSE-LONGITUDINAL TEMPERATURE EQUILIBRATION IN A LONG UNIFORM BEAM

Computer simulations are employed to examine the transfer of transvers e thermal energy to the longitudinal direction via a collective electr ostatic instability which is driven by an initial temperature anisotro py. The nature of the instability is illustrated using electrostatic p article-in-cell simulations in an axisymmetric geometry, but with thre e components of the velocity. Results are presented for a long coastin g space-charge-dominated beam, propagating in a uniform focused channe l to illustrate the development of a coherent mode structure with an a xial wavelength comparable with the beam diameter, and growth times co mparable with the betatron period.