Strong diffraction effects accompany the transmission of a laser beam through inhomogeneous plasma microstructures.

In the study we thoroughly analyze diffraction effects accompanying the laser beam transmission through inhomogeneous plasma microstructures and simulate their diffraction patterns at the object output and in the near field. For this we solve the scalar Helmholtz wave equation in the first Rytov approximation and compute the diffraction spreading of the transmitted beam in free space. Diffraction effects are found to arise within the beam passage through inhomogeneous plasma microstructures even in the simplest approximations of the laser beam interaction with plasma.

Natural sources of intense ultra-high-frequency radiation in high-voltage atmospheric discharges.

We study the sources of intense ultra-high-frequency (UHF) radiation (in the frequency range 1-6 GHz) arising during the development of high-voltage atmospheric discharges. The discharges were initiated in a long discharge gap by applying an approximately 1-MV pulse with positive or negative polarity. By employing a radio registration system based on ultrawideband antennas, we managed to localize the UHF radiation sources in the discharge with centimeter accuracy and investigate their temporal and spatial correlation with the discharge structures.

Electromagnetic emissions in the MHz and GHz frequency ranges driven by the streamer formation processes.

We provide comprehensive data on the spectral and temporal characteristics of low-frequency (LF) (MHz) and high-frequency (HF) (GHz) radio emissions and investigate their correlation with the streamer formation. We show that the propagation of streamers from the cathode is accompanied only by the LF radio emission (10-150 MHz). In contrast, the HF radio emission (1-4 GHz) arises during the travel of counterstreamers from the anode, which is also indicated by radio interferometric measurements.

Streamer formation processes trigger intense x-ray and high-frequency radio emissions in a high-voltage discharge.

For a laboratory discharge initiated in a long air gap by a microsecond megavolt pulse, we simultaneously register wideband high-frequency microwave and hard-x-ray emissions and thoroughly analyze the temporal relationship of the emissions depending on the discharge evolution. The temporal structure of microwave radiation is found to consist of numerous short intense bursts with high-frequency components. We directly show that x-ray and microwave emissions can appear almost synchronously in the discharge but only when a complex net of countless plasma channels forms and spans the entire discharge gap.

Precise optical registration of fine-structured electrical sparks and related challenges.

Fine-structured sparks naturally formed in electrical gas discharges are challenging objects of optical research. The veracity of the spark structure image obtained by laser probing techniques is still a subject for discussion due to possible distortions introduced by the employed optical setup. We thoroughly analyze this issue by simulating the spark image formation and evaluating the effect of the setup response function on the spark pattern quality.