Suppression of the particle generation from the emitter of the corona discharge air ionizer is one of the most important issues to maintain the clean room at low contamination level. The particle generation rate increases with increasing the ion creation rate, because the particles are generated by spattering effect of the generated ions. In order to find out the optimum operating condition by controlling the ion transportation efficiency, that is defined as the ratio of the ion number arrived at the working aria to the of ion number created at the emitter of the air ionizer, we investigated the relationship between the ion transportation efficiency and the frequency of the power supply as an operating condition of the air ionizer. The low frequency operation was suitable to suppress particle generation without reducing the static neutralization performance, because the ion transportation efficiency increased with decreasing the operating frequency.
