An Electrostatic Field-Driven Ionizer for a Moving Charged Target

An electrostatic field-driven (EFD) ionizer specifically designed for a moving charged target is proposed. The ionizer, which is proximally positioned to the charged target, is composed of a grounded mesh electrode and an array of positive and negative needle electrodes. The positive and negative needles face each other to make a high space charge density of positive and negative ions just above the grounded mesh. The electric field formed between the grounded mesh and the charged target transports ions by electrostatic force. The ion transportation brings a faster charge elimination rate than the air drag force widely used in commercial ionizers. An evaluation method of the charge elimination for a moving target is also proposed. The method employs parameters of capacitance of the target, equivalent resistance of the ionized air, effective length of the ionizing zone and moving speed of the target. The performance of the EFD ionizer and a commercial fan-type ionizer were compared using the evaluation method. The EFD ionizer was found to have significantly higher performance than the commercial fan-type ionizer.