Positron cooling in a magnetized electron beam

Relaxation of a positron beam in an electron gas moving in a magnetic field is studied. The case is considered when the longitudinal electron temperature is small compared to the transverse temperature. Expressions for the force of friction and scattering coefficients for the positron momenta are found for a low density electron beam when the time of flight through the electron cooling system is smaller than the plasma oscillation period. It is shown that in strong magnetic field the effective cross section for cooling of the longitudinal positron motion is determined by its longitudinal velocity relative to the electron gas. The closeness of the electron and positron Larmor rotation frequencies, in turn, sharply enhances the cooling intensity of the transverse degree of freedom of the positrons. Taken together these circumstances may be used to increase by many times the cooling of high-temperature positron beams