Operation of a Microwave Pulse Compressor With a Laser-Triggered Plasma Switch at Different Laser Beam Directions

Abstract

A resonant microwave pulse compressor with laser triggering of the plasma discharge in its switch was studied for the influence of the unfocused laser beam direction with respect to the RF electric field. The compressor was realized as a rectangular waveguide-based cavity connected to an H-plane waveguide tee with a shorted side arm filled with pressurized helium and pumped by a conventional pulsed S-band magnetron. It was found that neither the direction, nor the intensity of the laser beam significantly affect the compressor output pulse peak power and waveform. Meantime, the delay between the moment of plasma discharge initiation and the appearance of the microwave output is shorter and the time jitter for this delay is smaller if the laser beam is directed along the RF electric field. The same effect was observed when increasing the intensity of the laser beam. Time-resolved optical emission spectroscopy was used to evaluate the plasma density, and numerical simulations of the RF energy release from the system with the appearance of plasma showed a good agreement with the experimentally obtained characteristics of the plasma and microwave output pulse. Index Terms-Laser triggering, microwave pulse compression, plasma switch. Leonid Beilin received the B.Sc., M.Sc., and Ph.D. degrees in physics from the Technion-Israel Institute of Technology (Technion), Haifa, Israel, in 2006, 2010, and 2015, respectively. His Ph.D. research focused on nanosecond timescale plasma formation in the presence of highintensity electromagnetic field with the Plasma and

Self-consistent evolution of plasma discharge and electromagnetic fields in a microwave pulse compressor

“…13 The external ionization rate Q e in this case was set constant for a fixed time interval within the 8-mm-thick layer crossing the side arm waveguide at the antinode of the RF electric field. For the experimental configuration, to simulate laser triggering of the discharge, as in the experiments, [14][15][16] an initial population of particles was set in a small volume around the electric field antinode in the side arm, and Q e was calculated from Eq. (3).…”

“…(3). Since in the experiments, 15,16 the gas filling the system was helium, the attachment rate was set to zero, and the avalanche rate was derived from the empirical formula for the Townsend coefficient for inert gases (see Ref. 2).…”

“…Below, we employ one possible approach for producing external ionization-setting an initial population of seed electrons-to model the laser triggering used in our recent experiments. [14][15][16]…”

“…In addition to the model configuration of the compressor, same as in Ref. 11, we have also performed simulations for the geometry of the compressor studied in our experimental works [14][15][16] to compare the simulation results with those obtained in the experiments.…”

Improved operation of a microwave pulse compressor with a laser-triggered high-pressure gas plasma switch

“…4,5 Meanwhile, the efficiency of the power extraction from the compressor cavity remains rather low; values of 30%-40% were reported in an early paper, 2 and the same level was obtained in recent studies. 6,7 The efficiency of the power extraction is defined as the ratio of the peak output power to the available power at a given stored energy, i.e., the power of the traveling waves forming the standing wave in the cavity. Below we shall refer to this as the stored power.…”