We are developing a new type of microbeam system, intentionally utilizing the process of acceleration, accompanied with the beam contraction effect (conservation of normalized emittance). This device will enable one to produce microbeams for any ion species, less than 0.1 &mgr;m in diameter. A tentative design of lens system (ion energy=100 kV), composed of an entrance aperture lens and an einzel lens, will be described, and it will be discussed why the spherical aberration can be depressed much lower than the usual nonaccelerating lenses. The chromatic aberration due to the fluctuation of the acceleration voltage can be avoided in principle. Hence the only source of this type of aberration is the energy spread of the ion beam from the ion source. The maximum performance of this microbeam system may be obtained when the energy increasing ratio is large enough so that the incident beam energy is kept as low as possible. For investigating these points a hydrogen ion source of special design has been tested. It was found that the intrinsic energy spread can be made considerably low (∼0.5 eV) and a narrow parallel ion beam of several tens eV, which is nearly perfectly neutralized in space charge, can be obtained.