AbstractThe propagation stability of the charge-compensated two-component ion beam in the periodical quadrupole focusing channel are investigated in a linear approximation. The frequencies of transversal noncoherent oscillations are determined. Also, the frequencies of coherent dipole and quadrupole oscillations have been found. Compared with the noncoherent case these frequencies rapidly increase with current. It is shown that the most dangerous is the coherent quadrupole asymmetric mode, which determines the upper limit of the ion current.