Resonant Electric Field Research Articles

A Review on Resonant MEMS Electric Field Sensors

Electric field sensors (EFSs) are widely used in various fields, particularly in accurately assessing atmospheric electric fields and high-voltage power lines. Precisely detecting electric fields enhances the accuracy of weather forecasting and contributes to the safe operation of power grids. This paper comprehensively reviews the development of micro-electromechanical system (MEMS) resonant EFSs, including theoretical analysis, working principles, and applications. MEMS resonant EFSs have developed into various structures over the past decades. They have been reported to measure electric field strength by detecting changes in the induced charge on the electrodes. Significant advancements include diverse driving and sensing structures, along with improved dynamic range, sensitivity, and resolution. Recently, mode localization has gained attention and has been applied to electric field sensing. This paper reviews the performances and structures of MEMS resonant EFSs over recent decades and highlights recent advances in weakly coupled resonant EFSs, offering comprehensive guidance for researchers.

Single-molecule detection of SARS-CoV-2 N protein on multilayered plasmonic nanotraps with surface-enhanced Raman spectroscopy

The spread of the SARS-CoV-2 virus has had an unprecedented impact, both by posing a serious risk to human health and by amplifying the burden on the global economy. The rapid identification of the SARS-CoV-2 virus has been crucial to preventing and controlling the spread of SARS-CoV-2 infections. In this study, we propose a multilayered plasmonic nanotrap (MPNT) device for the rapid identification of single particles of SARS-CoV-2 virus in ultra-high sensitivity by surface-enhanced Raman scattering (SERS). The MPNT device is composed of arrays of concentric cylindrical cavities with Ag/SiO2/Ag multilayers deposited on the top and at the bottom. By varying the diameter of the cylinders and the thickness of the multilayers, the resonant optical absorption and local electric field were optimized. The SERS enhancement factors of the proposed device are of the order of 108, which enable the rapid identification of SARS-CoV-2 N protein in concentrations as low as 1.25 × 10−15－12.5 × 10−15 g mL−1 within 1 min. The developed MPNT SERS device provides a label-free and rapid detection platform for SARS-CoV-2 virus. The general nature of the device makes it equally suitable to detect other infectious viruses.

The study of the influence of the geometry of a lateral electric field resonator on its resonant characteristics

An experimental study of the dependence of the electrical impedance of a lateral electric field resonator on its thickness and the size of the gap between the electrodes was carried out. The resonator was made of PZT-19 piezoceramics in the form of a rectangular parallelepiped with the shear dimensions of 18 × 20 mm2. Two rectangular electrodes with a gap that varied in the range from 4 to 14 mm were applied on one side of the resonator. For each gap width, the frequency dependences of the real and imaginary parts of the electrical impedance were measured using an impedance analyzer. It has been found that increasing the gap width leads to an increase in the resonant frequency and to an increase in the maximum value of the real part of the impedance. Three series of such experiments were carried out for three values of the resonator thickness: 3.02, 2.38 and 1.9 mm. The resonant characteristics of the resonator were also theoretically analyzed by finite element analysis using two models. One resonator model was based on a two-dimensional finite element method. In this case, the vibration modes that existed due to the finite size of the plate in the direction parallel to the gap between the electrodes were not taken into account. The second model of the resonator used a three-dimensional finite element method, which correctly took into account all vibration modes existing in the resonator. Comparison of theory with experiment has shown that the three-dimensional model provides a better agreement between theoretical and experimental results.

Amplified linear and nonlinear chiral sensing assisted by anapole modes in hybrid metasurfaces

The interaction between chiral molecules and circularly polarized light is largely influenced by the local optical chirality density. This interaction prompts substantial demand of the design of nanophotonic platforms capable of enhancing such effects across large and accessible volumes. Such a magnification requires nanostructures that provide strong electric and magnetic field enhancements while preserving the phase relation of circular light. Dielectric nanostructures, particularly those able to support resonances, are ideal candidates for this task due to their capacity for high electric and magnetic field enhancements. On the other hand, efficient third harmonic generation requires strong electric field resonances within dielectric materials, a feature often boosted by incorporating plasmonic materials into hybrid systems. In this work, we numerically propose a coupled silicon disk-gold ring system that can exploit the anapole-induced field confinement to provide a broadband magnified circular dichroism under realistic conditions, reaching values up to a 230-fold enhancement. We also demonstrate that this structure can be employed as an efficient third harmonic generator, which, when integrated with chiral media, enables an 800-fold enhancement in circular dichroism. Furthermore, we show that pulsed illumination at intensities up to 10 GW/cm2 does not induce temperature increments that could potentially damage the samples. These findings suggest that this system can be a promising and versatile approach toward ultrasensitive chiral sensing.

Terahertz Sensing of L-Valine and L-Phenylalanine Solutions.

To detect and differentiate two essential amino acids (L-Valine and L-Phenylalanine) in the human body, a novel asymmetrically folded dual-aperture metal ring terahertz metasurface sensor was designed. A solvent mixture of water and glycerol with a volume ratio of 2:8 was proposed to reduce the absorption of terahertz waves by reducing the water content. A sample chamber with a controlled liquid thickness of 15 μm was fabricated. And a terahertz time-domain spectroscopy (THz-TDS) system, which is capable of horizontally positioning the samples, was assembled. The results of the sensing test revealed that as the concentration of valine solution varied from 0 to 20 mmol/L, the sensing resonance peak shifted from 1.39 THz to 1.58 THz with a concentration sensitivity of 9.98 GHz/mmol∗L-1. The resonance peak shift phenomenon in phenylalanine solution was less apparent. It is assumed that the coupling enhancement between the absorption peak position of solutes in the solution and the sensing peak position amplified the terahertz localized electric field resonance, which resulted in the increase in frequency shift. Therefore, it could be shown that the sensor has capabilities in performing the marker sensing detection of L-Valine.

Molecular Dynamics Simulation Combined with Near-Field Electromagnetic Analysis for Ultrashort-Pulsed Light-Induced Plasmonic Nanobubbles.

Ultrashort-pulsed light-induced nanobubbles gain great attention in research fields such as cancer therapy, optical imaging, and drug delivery. However, the mechanism governing the nucleation and growth of nanobubbles remains controversial. In this study, a molecular dynamics simulation combined with near-field electromagnetic theory is developed to investigate the influence of the localized surface plasmon resonance effect (LSPR) on nanobubble nucleation under various time-length pulsed light and to reveal the energy transfer differences during the nanobubble generation process. The results show that when silver nanoparticles (NPs) are irradiated by a 5 ps shorter-pulsed light, the temperature of the water layer adjacent to the nanoparticle surpasses that of the nanoparticle itself and reaches the spinodal temperature. This leads to nanobubbles' rapid nucleation at approximately 20 ps, which is 80 ps earlier than that irradiated by a 100 ps longer-pulsed light. Comparatively, during longer-pulsed light irradiation, a slower increase in both the temperature of the silver NPs and the water layer results in delayed nucleation of nanobubbles. Therefore, the plasmonic nanobubbles (PNBs) were observed around in 74 and 100 ps when irradiated by 50 and 100 ps longer-pulsed light, respectively. Moreover, the result indicates that the LSPR-induced enhanced electric field by shorter-pulsed light (5 ps) is 2.1 × 1010 V/m, which can accelerate the motion of water molecules surrounding silver NPs, resulting in rapid generation of nanobubbles. However, the intensities of the resonant electric field drop to 5.6 × 109 and 5.0 × 109 V/m when the duration times of pulsed light are 50 and 100 ps, respectively. These results indicate that the energy transfer mechanism of plasmonic nanobubbles (PNBs) under ultrashort-pulsed light irradiation might be very different from that of thermally mediated nanobubbles (TNBs). This work provides new insights into understanding the generation of PNBs induced by ultrashort-pulsed light.

Including the parallel mass flow in calculating the steady-state solutions and stability of the momentum balance equations for a quasisymmetric stellarator

The Helically Symmetric Experiment (HSX) is a quasisymmetric stellarator with minimal parallel viscous damping in a helical direction. The parallel flow (Vǁ) along the magnetic field is similarly weakly damped by viscosity. In this paper, the self-consistent steady-state parallel and poloidal momentum balance equations are used to show that a large Vǁ on the order of the ion thermal velocity can increase the ion resonant radial electric field (Er) beyond the value calculated using the typical approximation that Vǁ is zero. By altering the damping of Vǁ, either by degrading the quasisymmetry or varying the neutral density, the ion resonant Er can shift in a controllable fashion. It is shown explicitly that there exist stable and unstable steady-state solutions in the two-dimensional space of Vǁ and Er. A stability analysis of each solution is performed by calculating the eigenvalues and eigenvectors of the Jacobian. The unstable solution corresponds to a saddle point in which the eigenvalues have opposite signs. The analysis leads to the conclusion that unstable solutions occur when the derivative of the total poloidal damping with respect to Er is positive. A hysteresis in Er and Vǁ is observed when the radial current density is linearly increased to a maximum and then decreased back to zero. Jumps in the radial electric field and the parallel flow are observed as the radial current density drives the evolution from one stable point to the next. This result is similar to experimental data observed on several devices.

AC Current Sensor Based on Magnetoelectric Composites Transducers: Resonance Damping, Current Dynamic and Electric Field Disturbances

AC Current Sensor Based on Magnetoelectric Composites Transducers: Resonance Damping, Current Dynamic and Electric Field Disturbances

Piezoelectric PZT film-driven resonant torsional MEMS electric field sensor

Piezoelectric PZT film-driven resonant torsional MEMS electric field sensor

A Wafer-Level Vacuum-Packaged Vertical Resonant Electric Field Microsensor

A Wafer-Level Vacuum-Packaged Vertical Resonant Electric Field Microsensor

Tunable acoustic graphene plasmon enhanced nano-infrared spectroscopy

Nano-infrared spectroscopy (nano-IR) technology can exceed the diffraction limit of light, achieving infrared spectroscopic detection with a spatial resolution of about 10 nm, which is an important technical means for studying the chemical composition and structure of molecules on a nanoscale. However, the weak infrared absorption signals of nanoscale materials pose a significant challenge due to the large mismatch between their dimensions and the wavelength of infrared light. The infrared absorption signals of molecular vibrational modes are proportional to the squares of the electromagnetic field intensities at their positions, implying that higher electromagnetic field intensity can significantly improve the sensitivity of molecular detection. Acoustic graphene plasmons (AGPs), excited by the interaction between free charges in graphene and image charges in metal, exhibit strong optical field localization and electromagnetic field enhancement. These properties make AGPs an effective platform for enhancing nano-IR detection sensitivity. However, the fabrication of graphene nanostructures often introduces numerous edge defects due to the limitations of nanofabrication techniques, significantly reducing the electromagnetic field enhancement observed in experiments. Here, we use finite element simulation to theoretically propose a tunable enhanced nano-IR detection platform based on nanocavity-acoustic graphene plasmons (n-AGPs), which utilizes a graphene/air gap/gold nanocavity structure. This platform avoids needing the nanofabrication of graphene, thereby preventing defects and contamination from being introduced in processes such as electron beam exposure and plasma etching. By plotting the dispersion of n-AGP, it is found that n-AGP has a high wavelength compression capability comparable to AGP (<i>λ</i><sub>0</sub>/<i>λ</i><sub>AGP</sub> = 48). Additionally, due to the introduction of the gold nanocavity structure, n-AGP possess an extremely small mode volume (<i>V</i><sub>n-AGP</sub> ≈ 10<sup>–7</sup><inline-formula><tex-math id="M5">\begin{document}$ {{ \lambda }}_{0}^{3} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240489_M5.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20240489_M5.png"/></alternatives></inline-formula>, <i>λ</i><sub>0</sub> = 6.25 μm). By calculating the electric field intensity distribution (|<i>E</i><sub>norm</sub>|) and the normalized electric field intensity spectrum (i.e. the relationship between frequency and |<i>E</i><sub><i>z</i></sub>|/|<i>E</i><sub><i>z</i>0</sub>|) of the n-AGP structure, it is evident that due to the high electron density on the gold surface, electromagnetic waves can be reflected from the boundaries of the gold nanocavity and resonantly enhanced within the nanocavity. At the resonant frequency of n-AGP (1800 cm<sup>–1</sup>), the electric field inside the cavity is enhanced by about 50 times. In contrast, at similar resonant frequencies, the electric field enhancement factor of Graphene plasmon (resonant frequency 1770 cm<sup>–1</sup>) and AGP (resonant frequency 1843 cm<sup>–1</sup>) are approximately 3 and 2 times, respectively, significantly lower than that of n-AGP. Furthermore, by placing a protein film (60 nm wide and 10 nm high) under the graphene, we calculate the spectral dip depths caused by Fano resonance between n-AGP and AGP with the vibrational modes of protein molecules, thereby validating the enhancement factors of different modes for protein vibrational mode infrared absorption. For the amide-I band of proteins, the detection sensitivity of n-AGP is about 60 times higher than that of AGP. Additionally, we find that by adjusting the structural parameters of the gold nanocavity, including cavity depth, width, and surface roughness, the response frequency band of n-AGP can be modulated (from 1290 to 2124 cm<sup>–1</sup>). Specifically, as the cavity depth increases, the electric field enhancement of n-AGP is improved, and the wavelength compression capability of n-AGP decreases, causing the resonant frequency to be blue-shifted (from 1793 to 2124 cm<sup>–1</sup>). As the cavity width increases, the resonant frequency of n-AGP is red-shifted (from 1793 to 1290 cm<sup>–1</sup>), and the effectiveness of the gold nanocavity boundary in reflecting the resonant electric field within the cavity diminishes, resulting in a decrease in the electric field enhancement factor. With the gradual increase in the roughness of the gold nanocavity bottom, the effective depth of the gold nanocavity increases, causing the n-AGP resonant frequency to be blue-shifted (from 1793 to 1861 cm<sup>–1</sup>) and the electric field enhancement factor to increase. Moreover, by adjusting the Fermi level of graphene (from 0.3 to 0.6 eV), we achieve dynamic tuning of n-AGP (from 1355 to 1973 cm<sup>–1</sup>). As the Fermi level of graphene increases, the wavelength compression capability of n-AGP decreases, resulting in a blue-shift in the resonant frequency. Finally, by optimizing the structural parameters and Fermi level of n-AGP, and placing protein particles of different sizes (20, 15, and 10 nm high, all 10 nm wide) into the graphene/gold nanocavity structure, we verify the protein detection capability of n-AGP-enhanced nano-IR. We find that n-AGP can detect the vibrational fingerprint features of the amide-I band and amide-II band. For protein films (60 nm wide and 10 nm high), the sensitivity increased by approximately 300 times, and for a single protein particle (10 nm wide and 10 nm high), the sensitivity increased by approximately 9 times. This enhanced structure based on n-AGP holds promise for providing an important detection platform for nanoscale material characterization and single-molecule detection, with broad application potential in biomedicine, materials science, and geology.

Transcranial direct current stimulation as treatment for major depression in a home treatment setting (HomeDC trial): study protocol and methodology of a double-blind, placebo-controlled pilot study

IntroductionTranscranial direct current stimulation (tDCS) of prefrontal cortex regions has been reported to exert therapeutic effects in patients with major depressive disorder (MDD). Due to its beneficial safety profile, its easy mode of application, and its cost-effectiveness, tDCS has recently been proposed for treatment at home. This would offer new chances for regionally widespread and long-term application. However, tDCS at home must meet the new methodological challenges of handling and adherence. At the same time, data from randomized controlled trials (RCT) investigating this mode of application are still lacking. In this pilot RCT, we therefore investigate the feasibility, safety, and effectiveness of a new antidepressant tDCS application set-up.Methods and analysisThe HomeDC trial will be conducted as a double-blind, placebo-controlled, parallel-group design trial. Thirty-two study participants with MDD will be randomly assigned to active or sham tDCS groups. Participants will self-administer prefrontal tDCS for 6 weeks. Active tDCS will be conducted with anode over F3, cathode over F4, for 5 sessions/week, with a duration of 30 min/day, and 2 mA stimulation intensity. Sham tDCS, conversely, follows an identical protocol in regard to electrode montage and timing, but with no electric stimulation between the ramp-in and ramp-out periods. Both conditions will be administered either as a monotherapy or an adjunctive treatment to a stable dose of antidepressant medication. Adjunctive magnetic resonance imaging (MRI) and electric field (E-field) modelling will be conducted at baseline. Primary outcome is feasibility based on successfully completed stimulations and drop-out rates. The intervention is considered feasible when 20 out of 30 sessions have been fully conducted by at least 75% of the participants. Effectiveness and safety will be assessed as secondary outcomes.DiscussionIn the HomeDC trial, the technical requirements for a placebo-controlled tDCS study in a home-based treatment setting have been established. The trial addresses the crucial points of the home-based tDCS treatment approach: uniform electrode positioning, frequent monitoring of stimulation parameters, adherence, and ensuring an appropriate home treatment environment. This study will further identify constraints and drawbacks of this novel mode of treatment.Trial registrationwww.ClinicalTrials.gov. Trial registration number: NCT05172505. Registration date: 12/13/2021.

Exploring Partial Structural Disorder in Anhydrous Paraxanthine through Combined Experiment, Solid-State Computational Modelling, and Molecular Docking

Paraxanthine (PX), a major metabolite of caffeine, a protective agent against Alzheimer’s and Parkinson’s disease, and a promising drug for the treatment of post-COVID 2019 anosmia and ageusia, has been studied in the solid state and protein–ligand complex. Partial disorder in PX, caused by the methyl group at the N(7) position, has been modelled and discussed. The relationship between the unusual structural disorder and the propensity to form a specific system of non-covalent bonds was analyzed. Three 1H-14N NMR-NQR (nuclear magnetic resonance–nuclear quadrupole resonance) experimental techniques were used, namely multiple frequency sweeps, Larmor frequency scanning, and the two-frequency irradiation, followed by solid-state computational modelling (density functional theory, supplemented by quantum theory of atoms in molecules, 3D Hirshfeld surfaces, and reduced density gradient), and molecular docking approaches. New quantitative methods for estimating changes in the global pattern of interactions under the influence of rotation of the methyl group in N(7) based on the Pompeiu–Hausdorff and Bhattacharayya metrics and the Wasserstein distance have been proposed and applied. A spectrum consisting of 12 lines, indicating the presence of 4 chemically inequivalent nitrogen sites in the PX molecule, was recorded, and the lines’ assignment to particular sites was made. The influence of the methyl rotation on the eigenvalues and eigenvectors of the electric field gradient tensor, NQR parameters, and resonance line positions was modelled in the solid (GGA/RPBE, m-GGA/RSCAN) and cluster (Minnesota M062X hybrid). Three factors have been found to determine structural disorder in PX: larger crystal voids near the methyl at N(7) than at N(1) (opening the path for the disorder), hyperconjugation strongly affecting the density distribution in the five-membered ring, and the involvement of the methyl group at N(7) in many non-covalent bonds that intercept (capture) subsequent jumping protons. The Pompeiu–Hausdorff and Bhattacharayya metrics and the Wasserstein distance confirmed the changes in the distribution and strength of non-covalent interactions throughout the molecule as a result of methyl rotation. This effect is clearly visible regardless of the type of metric, and its order of magnitude is consistent with the modulation effect of the NQR spectra (experimental and calculated). Through molecular docking, it was discovered that the PX moiety in protein–ligand complexes adopt the same methyl group conformation at N(7) as in the solid state. It was found that the cooperation–competition between the C-H⋯O hydrogen bonds and C-H⋯H-C dispersion interactions is the crucial factor that impedes methyl rotation and induces structural disorder, as well as being an important factor in the formation of the protein–ligand complexes.

CUDA-based optical parametric oscillator simulator

The coupled-wave equations (CWEs) in nonlinear optics are the fundamental starting point in the study, analysis, and understanding of various frequency conversion processes in dielectric media subjected to intense laser radiation. In this work, a useful package for the modeling of optical parametric oscillators (OPOs) based on the Split-Step Fourier Method algorithm is presented. The algorithm is scripted in the CUDA programming language in order to speed up the calculations and obtain results in a relatively short time frame by using a graphics processing unit (GPU). Our results show a speedup higher than 50X for vector size of 214 in comparison with the analogous code scripted for running only in CPU. The package implements the CWEs to model the propagation of light in second-order nonlinear crystals widely used in optical frequency conversion experiments. In addition, the code allows the user to adapt the cavity configuration by selecting the resonant electric fields and/or incorporating intracavity elements. The package is useful for modeling OPOs or other mathematically similar problems. Program summaryProgram Title:cuOPOCPC Library link to program files:https://doi.org/10.17632/5djxwg4fbp.1Developer's repository link:https://github.com/alfredos84/cuOPOLicensing provisions: MITProgramming language: CUDANature of problem: The problem that is solved in this work is that of two or three coupled differential equations that describe the propagation of light in a second order nonlinear medium, allowing the three-wave mixing process. By placing the medium in an optical cavity, an optical parametric oscillator is formed. The optical cavity is modeled by including the appropriate boundary conditions for the differential equations. As a result we obtain the electric fields of the interacting waves in the time and frequency domains.Solution method: The coupled differential equations are solved using the well-known fixed-step Split-Step Fourier method. Due to the eventual computational demand that some problems may have, we chose to implement the coupled equations in the CUDA programming language. This allows us to significantly speed up simulations, thanks to the computing power provided by a graphics processing unit (GPU) card. The output files obtained are the interacting electric fields, which have to be analyzed during post-processing.

Electromagnetic-Thermal Coupling Study for RF Compression Cavity Applied to Ultrafast Electron Diffraction.

Ultrafast electron diffraction (UED) is a powerful tool for observing the evolution of transient structures at the atomic level. However, temporal resolution is a huge challenge for UEDs, mainly depending on the pulse duration. Unfortunately, the Coulomb force between electrons causes the pulse duration to increase continually when propagating, reducing the temporal resolution. In this paper, we theoretically design a radio frequency (RF) compression cavity using the finite-element method of electromagnetic-thermal coupling to overcome this limitation and obtain a high-brightness, short-pulse-duration, and stable electron beam. In addition, the cavity's size parameters are optimized, and a water-cooling system is designed to ensure stable operation. To the best of our knowledge, this is the first time that the electromagnetic-thermal coupling method has been used to study the RF cavity applied to UED. The results show that the RF cavity operates in TM010 mode with a resonant frequency of 2970 MHz and generates a resonant electric field. This mode of operation generates an electric field that varies periodically and transiently, compressing the electronic pulse duration. The electromagnetic-thermal coupling method proposed in this study effectively improves the temporal resolution of UED.

Satellite radio detection via dual-microwave Rydberg spectroscopy

Rydberg electric field sensors exploit the large number of Rydberg resonances to provide sensitivity over a broad range of the electromagnetic spectrum. However, due to the difficulty of accessing resonant Rydberg states at ultra-high frequency (UHF) and below, ubiquitous bands in the world's current wireless communications infrastructure, they currently fall, short in sensitivity in this range. We present a resonant Rydberg electric field sensor operating in the UHF band using a dual-optical dual-microwave spectroscopy scheme. Adding an additional microwave photon allows us to access transitions between Rydberg states with higher angular momentum (L=3→4), which have lower resonant frequencies than transitions typically used in Rydberg sensors. We discuss the applicability of this type of sensor across the UHF band and below and measure the resonant sensitivity of our system at 2.3 GHz to be 70(5) μV m−1 Hz−1∕2, 57 times better than the measured sensitivity with a far off-resonant probing scheme at this frequency. We also show the effectiveness of this sensing scheme by measuring Sirius XM satellite radio (2.320–2.345 GHz) received outside the laboratory and rebroadcast onto the atoms.

A Study of Dielectric Effects on Resonance Frequency of a Spit Ring Shaped Inclusion

Resonator designs are central to the development of subwavelength unit structures of metasurfaces to create exotic and unique electromagnetic properties by modifying the host structure to tune impinging electromagnetic waves. The act of intentional control of propagating electromagnetic fields are actively being explored in wireless radio environment control for sixth generation (6G) and beyond. In this paper, we study the effect of dielectric properties on electric field distribution and resonance frequency of a circular split ring resonator (SRR). The subwavelength resonator structure is modelled and simulated using High Frequency Structure Simulation (HFSS) software. Rogers RO3003 and RO3210 were used at different thickness to study the field distribution and its effect on resonance frequency of the SSR. The results show a decrease in resonance frequency of 38.41% from RO3002 (lower relative permeability of 3) to RO3210 (higher relative permeability of 10.2). With change in Rogers RO3210 thickness from 1mm to 1.525mm, the resonance frequency has changed from 5.5GHz to 5.2313 GHz. This indicates that the material composition of the substrate and the physical dimension of the SRR unit cell affects the resonance frequency of the structure.   &nbsp

MAS: a versatile Landau-fluid eigenvalue code for plasma stability analysis in general geometry

We have developed a new global eigenvalue code, multiscale analysis for plasma stabilities (MAS), for studying plasma problems with wave toroidal mode number (n) and frequency (ω) in a broad range of interest in general tokamak geometry, based on a five-field Landau-fluid description of thermal plasmas. Beyond keeping the necessary plasma fluid response, we further retain the important kinetic effects including diamagnetic drift, ion finite Larmor radius, finite parallel electric field (), ion and electron Landau resonances in a self-consistent and non-perturbative manner without sacrificing the attractive efficiency in computation. The physical capabilities of the code are evaluated and examined in terms of both theory and simulation. In theory, the comprehensive Landau-fluid model implemented in MAS can be reduced to the well-known ideal magnetohydrodynamic (MHD) model, electrostatic ion-fluid model, and drift-kinetic model in various limits, which clearly delineates the physics validity regime. In simulation, MAS has been well benchmarked with theory and other gyrokinetic and kinetic-MHD hybrid codes in a manner of adopting the unified physical and numerical framework, which covers the kinetic Alfvén wave, ion sound wave, low-n kink, high-n ion temperature gradient mode and kinetic ballooning mode. Moreover, MAS is successfully applied to model the Alfvén eigenmode (AE) activities in DIII-D discharge #159243, which faithfully captures the frequency sweeping of reversed shear AE, the tunneling damping of toroidal AE, as well as the polarization characteristics of kinetic beta-induced AE and beta-induced Alfvén-acoustic eigenmode being consistent with former gyrokinetic theory and simulation. With respect to the key progress contributed to the community, MAS has the advantage of combining rich physics ingredients, realistic global geometry and high computation efficiency together for plasma stability analysis in the linear regime.

A Hybrid EMC Testing Facility: Combining Transmission Line and Reverberation Chamber Measurement System

By combining a transmission line system (TLS) and a reverberation chamber (RC), a hybrid electromagnetic compatibility (EMC) testing facility is designed and constructed. Generally, the lowest usable frequency (LUF) of an RC is limited by its dimension, which limits the application of RCs for EMC testing at low frequencies. Therefore, to improve the field uniformity (FU) of an RC at frequencies lower than the LUF, a TLS is integrated into the RC. After optimizing the load resistance, length, and width of the TLS, the resonant frequency and electric field spikes of the hybrid system are eliminated. The FU of the E-field in the system is greatly improved in the frequency range of 0-30 MHz. Moreover, using an oscillating wall stirrer in the RC, the FU satisfies the standard (IEC 61000-4-21) above 80 MHz. Results show that combining the TLS and the RC testing system could be widely used for EMC testing in the frequency range of 0-30 MHz and 80 MHz-6 GHz.

Verification of the Effect of Local Electric Field Resonance Behaviors on the Transmission Properties of the Dual-Band Terahertz Metasurface

Verification of the Effect of Local Electric Field Resonance Behaviors on the Transmission Properties of the Dual-Band Terahertz Metasurface