Measurement of AC Ion Current from Ionizer by Using Faraday Cage
AC ionizer with high frequency became more common in semiconductor industries. Neutralization mechanism of such equipment is, however, not well understood because the measurement of extremely small ion current is interfered by AC induction. Our attempt is to use the Faraday cage that is directly connected to an AC ionizer. At frequencies of 1 Hz and 10 Hz, clear pulse shape ion currents were measured. The amounts of transported charges increase with both applied voltage and pressure. The effect of pressure is more significant than voltage. At higher frequency, the measured current changes from pulse to sinusoidal shape. From the delay time of 1 kHz, the average air velocity between the needle and Faraday cage was calculated. From DC corona measurement inside the nozzle, it became clear that the portion of transported charge to the Faraday cage is quite small.
Equivalent circuits for air ionizers used in static control
Abstract Air ionization systems can be described by an equivalent electrical circuit connecting a charged object to ground. This suggests an alternate characterization technique to the traditional charged-plate method that relies on measurements of charge decay time and balance voltages. The equivalent circuits for a variety of ionizers were obtained by measuring the current from a biased plate over a range of voltage, and then fitting these results to a circuit consisting of a resistance, a voltage source, and a saturation current. The ionizer is most effective when the resistance dominates, so that the decay of charge from the object follows an exponential decay law. The voltage source represents the offset voltage that an ungrounded object will acquire when exposed to the ionization system and the current represents the maximum ion output that can be extracted from the ionizer. The equivalent-circuit model has been incorporated into a technique called the biased-plate monitor (BPM) to provide an new way to describe air ionizer systems. The BPM is faster and more descriptive than the charged-plate method, and can also be made much smaller if the region of interest is confined. It also gives a better description of charge control effectiveness for very small (hard-disk heads) or very large (LCD) devices.
Simulation study of high power microwave generation by virtual cathode oscillation in coaxial vircator
Summary form only given, as follows. We have numerically simulated the high power microwave generation by virtual cathode oscillation in a coaxial vircator with 3 dimensional PIC code Magic. It is noted that the coaxial vircator has the advantage of an enhancement of power efficiency and gaining of narrow bandwidth frequency. The study is focused on the design of a diode structure for a coaxial vircator suitable for Chundoong IREB pulser (Max. 600 kV, 85 kA, 60 ns). It consists of a center annular cathode, a cylindrical meshed-anode and a reflector. The simulation results showed that the coaxial vircator can indeed be operated at the selected frequency with the narrow bandwidth and the microwave output power strongly depends on the position and geometry of the reflector. From this simulation results we expect that the maximum microwave output power will be obtained by the reflector of 4 cm in width and also 4 cm in distance away from the IREB, where the resonant frequency of microwave from coaxial vircator is simulated to be 6.577 GHz.