Abstract: Neutralized ion beams produced by two kinds of magnetically isulated ion diodes have been propagated over two meters in vacuum in the presence of a transverse magnetic field.Bt<400Gs.Diamagnetic and electric polarization measurementsverifythat the E×B drift mechanism governs the beam propagation both for the low β case (0.01<β<1) and the high β easel 1<β<300).where β=(4πnm₁r_n²·B²) is the ratio of beam kinetic energy to transverse magnetic field energy.In the high β case we observed fast diffusion of 6,into the beam which can be accounted for by a classical treatment.