Plasma-Profile Control in an ICP Reactor

ICP is widely used in electromagnetic scattering due to its high electron density and simple structure. The distribution of plasma parameters can affect the electromagnetic scattering, so the control of plasma parameter distribution is very important for aircraft stealth. Firstly, the effect of the number of coil turns on the plasma parameter distribution is analyzed. With the increase of the number of coil turns, the peak value of induced magnetic field decrease, the width of magnetic field increase and the homogeneity of plasma increase. Then, the Boltzmann solver is used to calculate the plasma electron energy distribution function at different positions under the four-turn coil. Finally, the influence of external circuit capacitance on plasma parameter distribution is analyzed. In this cavity structure, the electron density first increases and then decreases with the external circuit capacitance increase, and the peak value is on 75 pF. In this study, we propose a method to further regulate the plasma parameter distribution by using terminal capacitance to control the induced magnetic field.

Study on the Internal Mechanism of APD Photocurrent Characteristics Caused by the ms Pulsed Infrared Laser Irradiation

In this paper, the sampling current characteristics of the external circuit and the internal mechanism of the current generation in APD irradiated by a millisecond pulse laser were studied. The photocurrent of APD irradiated by a millisecond pulse laser with different energy densities was obtained by the sampling resistance of the external circuit. The photocurrent can be divided into a photocurrent stage, conduction stage and recovery stage in the time domain. This is mainly due to the carrier flow in APD, which leads to the lowering of the barrier between the PN junction. The research results of this paper can be extended to the response of the detector to the high-power infrared pulse laser and provide a certain experimental basis for the design of a millisecond pulse infrared laser detection circuit.

Electric Breakdown in Long Discharge Tubes at Low Pressure (Review)

The review is devoted to studies of the processes and mechanisms of ignition of a glow discharge in tubes whose length significantly exceeds their diameter (long discharge tubes) at low pressures (~10 Torr and lower) and moderate voltage rise rates (~1 kV/μs and lower). The electric field in such tubes before a breakdown is substantially nonuniform. Therefore, a breakdown occurs after an ionization wave (or waves) passes through the discharge gap at a speed of ~105–107 cm/s. This makes the characteristics of the breakdown in long tubes significantly different from the breakdown between large and closely spaced electrodes, where the electric field is uniform before the breakdown and where the Townsend or, under strong overvoltage, streamer mechanism is realized. On the other hand, the nature of these processes is very different from those occurring in nanosecond discharges, which arise at voltages with a steepness of ~1 kV/ns and higher and are associated with high-speed (~109 cm/s) ionization waves. The review is based on the materials of experimental and computational works published from 1938 to 2020. Breakdown processes, optical and electrical characteristics of the discharge gap during breakdown, and the influence of the external circuit parameters and external actions (shielding and illumination by external sources of visible radiation) are analyzed.