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The emittance of the compact microwave ion source for low energy application was investigated. The source structure was slightly modified from the previously reported version. The extraction apertures of 3 mm and 4 mm were used to evaluate the emittance. It was found that the normalized emittance of the present ion source ranged from 6 × 10(-8) m rad (3 mm extraction aperture) to 2 × 10(-7) m rad (4 mm extraction aperture), which are similar to that of the original ion source.

A low energy ion beam system for space charge compensation (SCC) experiments was developed and evaluated. This system was designed for observation of SCC of a positive ion beam with an electron beam. The system consisted of the ion source chamber and the SCC experiment chamber. The ion source chamber was equipped with the compact microwave ion source for low voltage extraction. Ion current at initial position of the analysis chamber was 84 microA at extraction voltage of 500 V, and satisfied a condition to observe the SCC effect clearly. In order to evaluate the SCC, we measured the arrival ion current by supplying thermionic electrons, which were extracted from a tungsten filament driven by ac voltage. As the electron supply, the arrival ion current increased from 40 to 68 microA at the potential of filament of +3 eV which produced the thermionic electron with extremely low energy extracted by space charge of the ion beam.