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A He gas-phase ion source having a three-electrode acceleration lens that can change the acceleration energy and magnification independently was developed. This source allows application of acceleration voltages up to 100 kV and extraction voltages up to 30 kV. This source is a component of our final objective of development, a nanometer lithography system with a beam diameter of 10 nm and a beam energy of 100 keV. In the present experiment, by using this source, the characteristics of He ion current emitted from W (111) emitter cooled by liquid N2 or liquid He was obtained. Maximum angular intensities of 40 nA/sr and 2.2 μA/sr were obtained at emitter temperatures of ∼100 and 20 K, respectively. In addition, the increase of the gas-phase ion current by emitter treatment (field-emission treatment or field-evaporation treatment) was ascertained.