In this paper, a high current ion modification system suitable for vacuum higher than 10-7 Pa has been developed. For maintaining such a high vacuum, a liquid metal ion source (LMIS), which hardly emits any gas molecules, has been employed. Then, a lens system, capable of focusing an ion beam of emission angle 60° extracted from the LMIS to a beam having a radius 2mm at 1m from the LMIS, has been designed by a numerical computer simulation method. In addition, a mass separator and a decelerating lens has been also designed and installed in the ion modification system. As a result, this system can produce a high purity metal ion beam with an energy in the range 10eV-10keV and ion current up to 20μA in a vacuum as high as 10-7 Pa, which sufficiently satisfies requirements of modification of substrates.
