Yang Cao

This study investigates the plasma formed by a ∼300 MW, ∼0.8 ns, ∼9.6 GHz high-power microwave (HPM) pulse propagating inside a waveguide filled by helium or hydrogen gas at different pressures. It was found that HPM traverses He and H2 gas at pressures 10 keV.

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 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.

An experimental method to measure the electric fields existing in a plasma wake produced by a ∼0.24 GW, ∼0.5 ns, 9.5 GHz microwave pulse traversing a plasma-filled waveguide is presented. The intensity of the second harmonic of a 30 fs 800 nm laser generated inside a gas-filled dielectric tube placed inside the waveguide is used to characterize the wakefield parameters. Three distinct decaying oscillations of the plasma wakefield, with peak amplitude of ∼20 kV/cm, were observed. The experimental results were confirmed by 3D large-scale plasma particle-in-cell simulations.

It was observed experimentally that after crossing a waveguide filled with a neutral gas, a short powerful microwave pulse leaves a periodic glow of plasma along the waveguide, persisting several tens of nanoseconds. A theoretical model is presented which in combination with numerical simulations proposes a possible explanation of this phenomenon.

It was observed experimentally that after crossing a waveguide filled with a neutral gas a short powerful microwave pulse leaves a periodic glow of plasma along the waveguide, persisting for several tens of nanoseconds. A theoretical model is presented which in combination with numerical simulations proposes a possible explanation for this phenomenon.

As semiconductor manufacturing moves into the nanotechnology era, mixed-size standard cell circuit designs have become mainstream, but they also pose significant challenges to placement. To address the mixed-size standard cell circuit legalization problem, in this paper, we first formulate it as a quadratic programming problem with nonnegative constraints, resulting in an equivalent linear complementarity problem (LCP). In particular, the system matrix involved in the LCP is positive semi-definite, so we perturb it to a positive-definite matrix. Then, we cast the linear complementarity problem as an equivalent implicit fixed-point equation. To improve the convergence rate of the class of modulus-based matrix splitting iteration method (MMS), we develop a robust two-step MMS to solve the fixed-point equation. Finally, we analyze the convergence property and illustrate the approximation of the solution between the perturbed LCP and the original LCP. Numerical experiments for the legalization problem are provided, and the results reveal that our approach is competitive with the existing state-of-the-art methods for solving mixed-size cell circuit legalization problems.

This article reports on attempts at direct detection of the wakefield, excited by a ≤1.2-GW, 25.5-GHz, <0.3-ns microwave pulse injected into a ~1010-cm−3 plasma-filled cylindrical waveguide.

Plasma wakefield generation by a ≤ 1.2 MW, 25.5 GHz, < 0.6 ns High Power Microwave beam injected into a ~10 10 cm -3 plasma filled circular waveguide is experimentally verified by applying a probing electron beam in the transverse direction to the wave propagation. We present LSP simulation results which confirm that observed experimental behavior of the probing beam follows the plasma density modulations in the wake of the microwave pulse.