A longitudinal compression is indispensable in a final stage
of the heavy ion driver system using a particle accelerator.
For the beam compression, an induction buncher applies the bunching
voltage so as to make a considerable velocity tilt between the
head and the tail of the beam bunch. However, the velocity tilt
induces mismatch oscillation of the beam envelope due to the
nonconformity between the beam particle velocity and the
confinement force of the lens system. At the first step of design
works for the beam transport line, the initial phase advance
is decided to avoid resonance lines on the tune diagram. However,
as the phase advance changes in the buncher by the velocity
tilt, the beam bunch reenters in the resonance condition under
certain circumstances. The transport region for avoiding the
resonance condition is discussed on a phase diagram, as a function
of the phase advance and the velocity tilt.