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

Shlapakovski, A.; Beilin, Leonid; Hadas, Yuval; Schamiloglu, E.; Krasik, Yakov E.

doi:10.1109/tps.2015.2436055

Cited by 4 publications

(10 citation statements)

References 8 publications

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“…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).…”

Section: Simulated Configurations and Plasma Modelmentioning

confidence: 99%

“…(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).…”

Section: Simulated Configurations and Plasma Modelmentioning

confidence: 99%

“…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]…”

Section: A Model Configurationmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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Nanosecond-scale evolution of plasma and RF electromagnetic fields during the release of energy from a microwave pulse compressor with a plasma interference switch was investigated numerically using the code MAGIC. The plasma was simulated in the scope of the gas conductivity model in MAGIC. The compressor embodied an S-band cavity and H-plane waveguide tee with a shorted side arm filled with pressurized gas. In a simplified approach, the gas discharge was initiated by setting an external ionization rate in a layer crossing the side arm waveguide in the location of the electric field antinode. It was found that with increasing ionization rate, the microwave energy absorbed by the plasma in the first few nanoseconds increases, but the absorption for the whole duration of energy release, on the contrary, decreases. In a hybrid approach modeling laser ignition of the discharge, seed electrons were set around the electric field antinode. In this case, the plasma extends along the field forming a filament and the plasma density increases up to the level at which the electric field within the plasma decreases due to the skin effect. Then, the avalanche rate decreases but the density still rises until the microwave energy release begins and the electric field becomes insufficient to support the avalanche process. The extraction of the microwave pulse limits its own power by terminating the rise of the plasma density and filament length. For efficient extraction, a sufficiently long filament of dense plasma must have sufficient time to be formed. V

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Section: Simulated Configurations and Plasma Modelmentioning

confidence: 99%

Section: Simulated Configurations and Plasma Modelmentioning

confidence: 99%

Section: A Model Configurationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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“…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.…”

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confidence: 99%

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

2016

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The influence of laser beam parameters on the output pulses of a resonant microwave compressor with a laser-triggered plasma switch was investigated. The S-band compressor, consisting of a rectangular waveguide-based cavity and H-plane waveguide tee with a shorted side arm, was filled with pressurized dry air and pumped by 1.8-ls-long microwave pulses of up to 450 kW power. A Nd:YAG laser was used to ignite the gas discharge in the tee side arm for output pulse extraction. The laser beam (at 213 nm or 532 nm) was directed along the RF electric field lines. It was found that the compressor operated most effectively when the laser beam was focused at the center of the switch waveguide cross-section. In this case, the power extraction efficiency reached $47% at an output power of $14 MW, while when the laser beam was not focused the maximal extraction efficiency was only $20% at $6 MW output power. Focusing the laser beam resulted also in a dramatic decrease (down to <1 ns) in the delay of the output pulses' appearance with respect to the time of the beam's entrance into the switch, and the jitter of the output pulses' appearance was minimized. In addition, the quality of the output pulses' waveform was significantly improved.

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Studies of gas ionization by high-power, sub-nanosecond microwave pulses

Maksimov,

Cao,

Haim

et al. 2024

Physics of Plasmas

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This study investigates the ionization pressure threshold of a gas (air, helium, argon, and SF6 across a wide pressure range) filled dielectric tube when a ∼300 MW, ∼0.7 ns, 9.6 GHz high-power microwave (HPM) pulse propagates through it. The thresholds are determined as the pressure for which the energy of the transmitted HPM pulse decreases to ∼30%, which is close to the same HPM pulse's transmission coefficient when a metal rod fills the tube. These thresholds are found to be 0.4 × 105 Pa,105 Pa, 1.8 × 105 Pa, and 0.2 × 105 Pa, for air, argon, helium, and SF6, respectively. The measured intensity of the plasma light emission starts to decrease at a pressure which coincides with the pressure threshold determined by HPM pulse propagation. Additionally, at gas pressures <5 × 104 Pa, it is shown that time- and space-resolved images of the light emission display a diffused plasma which at higher pressures >105 Pa transforms into streamer like plasma. Simplified numerical simulations of a microwave discharge in air at 1 × 105 Pa and 4 × 105 Pa are consistent with the experimental plasma light observations.

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

Cited by 4 publications

References 8 publications

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

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

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

Studies of gas ionization by high-power, sub-nanosecond microwave pulses

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