A planar electrode (collector) is immersed into a weakly magnetized discharge plasma column. Positive voltage steps are applied to the collector and time resolved measurements of the plasma response are performed by emissive probes using standard boxcar technique. On the emissive probe characteristics an interesting phenomenon is observed: a few μs after the application of the voltage step to the collector (time depends on the distance between the collector and the probe), the emissive probe starts to collect additional positive current in the potential region between plasma potentials of the high and low potential plasma. This phenomenon is investigated experimentally. We give a possible qualitative explanation that additional positive current collection is due to a combination of an interaction between the collector and the probe and space charge effects of positive ions around the probe. 相似文献
As an emerging topic, photonic‐assisted microwave measurements with distinct features such as wide frequency coverage, large instantaneous bandwidth, low frequency‐dependent loss, and immunity to electromagnetic interference, have been extensively studied recently. In this article, we provide a comprehensive overview of the latest advances in photonic microwave measurements, including microwave spectrum analysis, instantaneous frequency measurement, microwave channelization, Doppler frequency‐shift measurement, angle‐of‐arrival detection, time–frequency analysis, compressive sensing, and phase‐noise measurement. A photonic microwave radar, as a functional measurement system, is also reviewed. The performance of the photonic measurement solutions is evaluated and compared with the electronic solutions. Future prospects using photonic integrated circuits and software‐defined architectures to further improve the measurement performance are also discussed.
