Effect Of Field Amplification Research Articles

Role of electrostatic perturbation on kinetic resistive wall mode with application to spherical tokamak

A more complete non-perturbative magnetohydrodynamic (MHD)-kinetic hybrid formulation is developed by including the perturbed electrostatic potential δφ in the particle Lagrangian. The fluid-like counter-parts of the hybrid equations, in the Chew-Goldberger-Low high-frequency limit, are also derived and utilized to test the new toroidal implementation in the MARS-K code. Application of the updated non-perturbative hybrid model for a high-β spherical tokamak plasma in MAST finds that the perturbed electrostatic potential generally plays a minor role in the n = 1 (n is the toroidal mode number) resistive wall mode instability. The effect of δφ is largely destabilizing, with the growth rate of the instability increased by several (up to 20) percent as compared to the case without including δφ. A similar relative change is also obtained for the kinetic-induced resonant field amplification effect at high-β in the MAST plasma considered. The updated capability of the MARS-K code allows quantitative exploration of drift kinetic effects on various MHD instabilities and the antenna-driven plasma response where the electrostatic perturbation, coupled to magnetic perturbations, may play important roles.

Study on the influence of local optical field amplification effect on laser-induced damage of fused silica materials

Fused silica is an important part of optical components in large laser systems. Due to the limitation of manufacturing process, impurities and defects in the optical element would greatly reduce the service life of the optical element, and significantly reduce the final output of the laser performance. Aiming at the modulation effect of the internal defect of the component on the internal optical field of the component, the theoretical, simulation and experimental research are carried out. The results show that in the double-bubble impurity coupling, under the same radius R, when the impurity spacing is 1 λ, the local optical field amplification has a maximum value. The effect is equivalent to single-bubble modulation with radius 2 R–3 R. There is an extreme point of the modulated optical field between the air and fused silica crossing line for bubble impurities of different radii. The optical field modulation of small radius impurities is distributed behind the bubble impurities, and the modulation effect of large radius impurities is the maximum when the spacing is 2 λ. The temperature distribution curve of the fused silica element modulated by bubble impurities is consistent with the optical field distribution curve, showing a trend of decreasing slope. The presence of bubble impurities will cause the surface combustion wave of the component to flash and accelerate, and the bubble impurities will increase the generation and expansion rate of the surface combustion wave. This study provides a basis for reducing the uneven distribution of laser energy during the interaction between laser and fused silica, improving the lifetime of the overall optical system, and experimental measurement and analysis.

Superconductor/magnetoresistance mixed sensor with magnetic flux guides for in-plane magnetic field measurement

A superconductor/magnetoresistance (SC/MR) mixed sensor often has very high-precision detection capability, but it is only sensitive to the out-of-plane magnetic field that is perpendicular to the superconducting flux-to-field transformation amplifier (SFTA). This inherent characteristic makes it impossible for a primary SC/MR mixed sensor to measure the in-plane magnetic field, which limits its application in many fields. This paper presents a new architecture of SC/MR mixed sensors with two magnetic flux guides (MFGs) to realize in-plane magnetic field measurement, which is attributed to the combined effects of MFGs and SFTA. The finite element method simulations are used to study the magnetic flux converting effect of MFGs and magnetic field amplification effect of SFTA, which theoretically proves the feasibility of in-plane magnetic field measurement and reveals the influences of the sizes and spacing of MFGs on magnetic field magnification. Experimental results show that the SC/MR mixed sensor with MFGs can simultaneously sense the in-plane and out-of-plane magnetic fields, and the performance of the mixed sensor with MFGs is comparable to the primary one. The magnification and resolution of the mixed sensors with MFGs to the in-plane magnetic fields are, respectively, improved by 2.91 times and 2.23 times compared to those without MFGs to the out-of-plane magnetic fields. The work described in this paper is of great significance for the development of three-component weak magnetic field detection.

Superconducting magnetic flux transformation amplifier for the superconductor/magnetoresistance mixed magnetic sensor: Finite element simulation method and experimental verification study

The superconductor/magnetoresistance (MR) mixed magnetic sensor, which is composed of a superconducting magnetic flux transformation amplifier (SMFTA) and a MR sensitive element, has extremely great development potential in weak magnetic field detection because of its excellent sensitivity, simple structure and small size. However, it still lacks an effective method to study the spatial distribution of the magnetic field produced by SMFTA. Here, a finite element simulation method was proposed to study the magnetic field amplification effect of the SMFTA. Several factors affecting the magnetic field amplification were studied via this simulation method. Furthermore, mixed magnetic sensors with three typical sizes were successfully fabricated, and the experimentally measured magnifications of the three sensors were basically consistent with the simulation values, demonstrating the reliability of this simulation method. Our works are expected to pave a meaningful way for the SMFTA design and promote the development of superconductor/MR mixed magnetic sensors.

Molecular ferroelectric/semiconductor interfacial memristors for artificial synapses

With the burgeoning developments in artificial intelligence, hardware implementation of artificial neural network is also gaining pace. In this pursuit, ferroelectric devices (i.e., tunneling junctions and transistors) with voltage thresholds were recently proposed as suitable candidates. However, their development is hindered by the inherent integration issues of inorganic ferroelectrics, as well as poor properties of conventional organic ferroelectrics. In contrast to the conventional ferroelectric synapses, here we demonstrated a two-terminal ferroelectric synaptic device using a molecular ferroelectric (MF)/semiconductor interface. The interfacial resistance can be tuned via the polarization-controlled blocking effect of the semiconductor, owing to the high ferroelectricity and field amplification effect of the MF. Typical synaptic features including spike timing-dependent plasticity are substantiated. The introduction of the semiconductor also enables the attributes of optoelectronic synapse and in-sensor computing with high image recognition accuracies. Such interfaces may pave the way for the hardware implementation of multifunctional neuromorphic devices.

Flexible multilayer lead-free film capacitor with high energy storage performances via heterostructure engineering

The immense potential of flexible energy storage materials applied in wearable electronic devices has stimulated a lot of science researches on manufacturing technology and performance optimization. Herein, an all-inorganic flexible ferroelectric film with multilayer heterostructure is prepared based on Mn doped Bi0.5Na0.5TiO3BiNi0.5Zr0.5O3 (Mn:BNT-BNZ) and Bi0.5Na0.5TiO3BiZn0.5Zr0.5O3 (BNT-BZZ) relaxor ferroelectrics. A win-win situation of breakdown strength and polarization is achieved in the Mn:BNT-BNZ/BNT-BZZ multilayer film with the stacking period N = 3, of which energy density and efficiency reach 80.4 J/cm3 and 62.0% respectively. It is proposed that the excellent energy storage performances are attributed to the synergistic effect of the electric field amplification effect, interface blocking effect and the polarization coupling effect based on the multilayer heterostructure. Moreover, the flexible ferroelectric film exhibits outstanding temperature (25–205 °C), frequency (0.5–5 kHz) stability and antifatigue property (1 × 108 cycles), and can well maintain stable performance at different tensile/compressive bending radii (10–5 mm) and even after 104 bending cycles with a fixed bending radius of 3 mm. This work opens up a promising route to the development of flexible energy storage materials.

Numerical inside view of hypermassive remnant models for GW170817

The first multimessenger observation attributed to a merging neutron star binary provided an enormous amount of observational data. Unlocking the full potential of this data requires a better understanding of the merger process and the early post-merger phase, which are crucial for the later evolution that eventually leads to observable counterparts. In this work, we perform standard hydrodynamical numerical simulations of a system compatible with GW170817. We focus on a single equation of state (EOS) and two mass ratios, while neglecting magnetic fields and neutrino radiation. We then apply newly developed postprocessing and visualization techniques to the results obtained for this basic setting. The focus lies on understanding the three-dimensional structure of the remnant, most notably the fluid flow pattern, and its evolution until collapse. We investigate the evolution of mass and angular momentum distribution up to collapse, as well as the differential rotation along and perpendicular to the equatorial plane. For the cases that we studied, the remnant cannot be adequately modeled as a differentially rotating axisymetric NS. Further, the dominant aspect leading to collapse is the GW radiation and not internal redistribution of angular momentum. We relate features of the gravitational wave signal to the evolution of the merger remnant, and make the waveforms publicly available. Finally, we find that the three-dimensional vorticity field inside the disk is dominated by medium-scale perturbances and not the orbital velocity, with potential consequences for magnetic field amplification effects.

Field amplification effect of resonant magnetic perturbation on ion orbits in tokamak plasma

<sec> The fast ion transport associated with resonant magnetic perturbation (RMP) contains rich physical spanning single particle motion of fast particle and plasmas response physics with RMP and their interaction. Full numerical simulation considering such physical ingredients should be performed in a long run for clarifying the underlying physical features of the fast ion confinement with RMP. Thus, the appropriate application of RMP is not only to avoid the detrimental effects but also to serve as an actuator to exert targeted control over the energetic particle profile. To achieve this goal, a comprehensive knowledge of the effects of RMP including plasma response on fast ions is necessary. </sec> <sec> In this work, the plasma response to RMP in HL-2A device is simulated by the MARS-F code under different parameters including finite resistivity, toroidal rotation frequency and toroidal mode number, and the three-dimensional (3D) magnetic field topology considering RMP is obtained. Then, Boris algorithm is used to track the ion orbit under these 3D fields, and the physical mechanism of ion orbit characteristics changed by the perturbed field is explored in detail. It is found that with the increase of finite resistivity, the average value of perturbed magnetic field decreases, and the orbit radial expansion turns smaller. The variation of toroidal rotation frequency can change the distribution of perturbed magnetic field, resulting in different orbit radial expansions for different kinds of orbits. What is more, if the toroidal mode number increases, the amplitude of perturbed magnetic field after response decreases obviously, thus resulting in little effect on orbit radial expansion. In a word, the plasma responded RMP field enhances the orbit radial expansion, and the maximum orbital radial expansion increases with the augment of average value of perturbed magnetic field on the orbit. Meanwhile, the amplitude of orbit expansion increases significantly when the ions pass through the region where the perturbed magnetic field is strongly amplified. This effect can explain the increase of ion prompt loss and enhancement of plasma radial transport in edge localized mode mitigation experiments by RMP. </sec>

Sensitive colorimetric detection of Pb2+ by geometric field amplification and surface plasmon resonance visualization

Pb2+ is one of the major environmental pollutants, which can be visually detected by surface plasmon resonance of nanoparticles. Paper based analytical device, as a newly developed microfluidic detection platform, is featured in cost-effective and suitable for on-site analysis. In this paper, a sensitive and portable detection method for Pb2+ was proposed, in which Pb2+ was electrokinetically stacked on the paper fluidic channel by geometric field amplification effect and visualized online by glutathione-modified silver nanoparticles. Colorimetric quantification of the visualized stacking band was conducted by smart phone camera. To avoid unfavorable influence from pH change on the surface plasmon resonance visualization, field amplification effect was introduced by geometric design of the paper fluidic channel. The enriched Pb2+ was clearly visible on the paper substrate, and the stacking band intensity was about four orders of magnitude enhanced, comparing to the intensity without stacking. A linear response to Pb2+ was observed in the range of 0.3–7.0 μM (R2 = 0.997) with a limit of detection of 86 nM and a limit of quantity of 0.28 μM. The established method was used in the detection of Pb2+ from river and lake water samples, and the results were confirmed by atomic absorption spectroscopy method.

The Simulation of Tangshan Earthquake Intensity Field Based on Stochastic Finite Fault Model

The random ground motion simulation method based on the finite fault model is one of the proven methods in the field of simulating high frequency ground motion. Taking the extreme earthquake zone of the Tangshan earthquake in 1976 as the research goal, by combing the research results of the predecessors, the calculation model of the target zone was established and the parameters of the source model were determined. The local site data and the site dynamics parameters of the target zone were utilized. The quarter-wavelength method is used to obtain the local field amplification effect parameters. The strong ground motion simulation results of Tangshan earthquake are given by using the stochastic finite-fault model. The reliability and applicability of the method is confirmed by comparing with the historical seismic macro-intensity. The results will help improve the seismic design accuracy of the project in areas lacking strong vibration observation records, and have certain reference value and engineering significance for the development of urban earthquake prevention and disaster prevention measures.

Development of a bioaffinity SPR immunosensor based on functionalized graphene oxide for the detection of pregnancy-associated plasma protein A2 in human plasma.

BackgroundGraphene-like material such as functionalized carboxyl-graphene oxide (carboxyl-GO) can be intelligently tuned to achieve particular properties for biological and chemical sensing applications.MethodsIn this study, we propose a method to improve interference of non-specific proteins for use in human plasma assays. The highly specific interactions between molecules are an advantage of carboxyl-GO-based surface plasmon resonance (SPR) immunoassays, and this can be applied to spiked plasma samples with pregnancy-associated plasma protein A2 (PAPPA2).ResultsThe experiment results showed that carboxyl-GO could be used to modulate the plasmon resonance energy, work function and conductivity properties. In addition, carboxyl groups could be used to enhance the conduction of electrons between carboxyl-GO and Au electrodes due to the excellent conductivity and electron transfer rate. The carboxyl-GO-based SPR chip exhibited high sensitivity based on the electric field amplification effects of the composite dielectric material. Therefore, the surface electric field could be enhanced by electron transfer, thereby greatly improving the sensitivity of the sensing system. Enhanced electric field intensity was generated around the carboxyl-GO of 63.58 V/m, and the measured work function was 4.95 eV. The results showed that the carboxyl-GO-based SPR biosensor had high sensitivity, affinity and selective ability for PAPPA2 protein with a high association rate constant (ka) of 3.1 ×109 M-1 S-1 and a limit of detection of 0.01 pg/mL in spiked human plasma.ConclusionThe results showed a detection accuracy of protein in spiked plasma of >90% compared to PBS buffer, suggesting that the carboxyl-GO-based SPR biosensor could be used in assays of human plasma for early and late gynecological diseases. The future of this technology will be useful for the diagnosis and evaluation of the risk of early maternal preeclampsia and potentially in clinical applications for gestational diseases.

Novel field amplification for sensitive colorimetric detection of microalbuminuria on a paper-based analytical device

Field-amplified stacking (FAS) is a commonly used method for enhancing the sensitivity of charged species from low conductive media in capillary electrophoresis. FAS also showed significant sensitivity enhancement effect on a uniform paper fluidic channel by proper design of the electrolyte. In this paper, a novel method of introducing electric field gradient is proposed by geometry design of a 2D paper fluidic channel, and field amplification effect was successfully demonstrated with reduced requirement on the sample's conductivity. Sensitive colorimetric detection of microalbuminuria (MAU) from urine samples was demonstrated by mobile phone camera. Experimental results showed that, with active electric field motivation, up to 93.5% of the loaded protein probe could be effectively transferred and stacked into a narrow band on the newly designed paper fluidic channel. A limit of detection (LOD) of 6.5 mg‧L−1 HSA was achieved with a dynamic range of 10–300 mg‧L−1 (linear in the range of 10–100 mg‧L−1, R2 = 0.991). Combined with selective staining of albumin with bromophenol blue (BPB), the established method was applied to the detection of MAU from clinical urine samples, and consistent results with that of the clinical method were obtained. With this paper-based analytical device (PAD), MAU from highly conductive urine samples can be directly loaded and detected without any pretreatment. This method provides a way to develop highly sensitive point-of-care test (POCT) for rapid screening of some diseases.

Simultaneous electrokinetic stacking and separation of anionic and cationic species on a paper fluidic channel.

On-line enrichment is effective for improving the sensitivity of paper-based analytical devices (PADs). Electrokinetic stacking of ionic species - anionic or cationic species, respectively, on a paper-based fluidic channel has been well demonstrated in the literature. In this work, we further demonstrated that both anionic and cationic species can be electrokinetically stacked and separated simultaneously on the same paper fluidic channel. The feasibility of the proposed method was visually demonstrated by using a colored cationic probe of Rhodamine 6G and an anionic probe of Brilliant Blue. With the introduction of a background electrolyte (BGE) consisting of weak acid and weak base salt, two electric field gradients can be developed on the same paper fluidic channel when a DC voltage was applied. Both of the anionic and cationic species from the reservoirs can be simultaneously stacked as separate bands on the two field gradients, respectively. Under optimized conditions, two orders of magnitude enrichment factors can be achieved for the anionic and cationic probes as characterized by colorimetric analysis by smartphone imaging. The applicability of this method was further demonstrated by stacking and separation of copper ions/nitrite and even amphoteric ions-proteins of phycocyanin (blue, pI 4.4)/cytochrome C (brown, pI 10.2). Potential applications can be found not only for a PAD based point of care test (POCT), but also for sample pretreatment in protein analysis considering the friendliness of the BGE to the mass spectrometer.

Sensitive colorimetric detection of Cu2+ by simultaneous reaction and electrokinetic stacking on a paper-based analytical device

Paper-based analytical device (PAD) with image-based colorimetric detection is advantageous in low-cost, fast, simple and suitable for on-site rapid analysis. However, the detection capability is normally limited. In this paper, a new method was proposed that combined a complex reaction and electrokinetic stacking, and the sensitivity of PAD was effectively increased as demonstrated by the colorimetric detection of Cu2+ with smartphone. A T-type paper fluidic channel was designed to realize the on-line complex reaction between polyethyleneimine (PEI) and Cu2+. Under electric field, positively charged PEI and Cu2+ were driven through the two channels and eventually met on the same paper fluidic channel to form the positively charged complex of dark blue color. Meanwhile, the complex was stacked into a narrow and enhanced color band by field amplification effect. Under optimal experiment conditions, the band intensity was increased by three orders of magnitude compared with that of direct Cu2+ imaging on the same paper substrate. A linear relationship in the range of 0.1–1.0mM Cu2+ was obtained (R2=0.991), and a limit of detection of 30μM was achieved, which is close to that by a desktop spectrophotometer. The selectivity of this method to other co-existing metal ions was also investigated. This work shows that by integration of a complex reaction and electro kinetic stacking, the sensitivity of image-based colorimetric detection can be greatly enhanced for rapid detection of Cu2+ by PAD.

Simultaneous electrokinetic concentration and separation of proteins on a paper-based analytical device

Electrokinetic concentration and separation of proteins was achieved simultaneously on a paper based analytical device based on the field amplification effect.

Ultralow-voltage field-ionization discharge on whiskered silicon nanowires for gas-sensing applications

Several hundred million volts per centimetre of electric-field strength are required to field-ionize gas species. Such fields are produced on sharp metallic tips under a bias of a few kilovolts. Here, we show that field ionization is possible at dramatically lower fields on semiconductor nanomaterials containing surface states, particularly with metal-catalysed whiskers grown on silicon nanowires. The low-voltage field-ionization phenomena observed here cannot be explained solely on the basis of the large field-amplification effect of suspended gold nanoparticles present on the whisker tips. We postulate that field penetration causes upward band-bending at the surface of exposed silicon containing surface states in the vicinity of the catalyst. Band-bending enables the valence electron to tunnel into the surface states at reduced fields. This work provides a basis for development of low-voltage ionization sensors. Although demonstrated on silicon, low-voltage field ionization can be detected on any sharp semiconductor tip containing proper surface states.

High-frequency electric field amplification in a magnetized plasma

In the investigation of cyclotron ion heating in systems designed for plasma isotope separation, the high-frequency (HF) electric field amplification effect was found to occur in equilibrium plasma. In the present article this effect is treated as a result of the interaction of the plasma placed in a constant external magnetic field with the HF modes of the vacuum chamber. Consistent elaboration of this approach allowed obtaining a clear interpretation of the HF electric field amplification effect and constructing a simple model of HF field excitation in a plasma column embedded in the external magnetic field.

TWO-PHOTON NONLINEAR INTERACTION MEDIATED BY CAVITY QUANTUM ELECTRODYNAMICS SYSTEMS

Exploiting the field-amplification effect of a cavity, the possibility of optical nonlinearity by only two photons was indicated experimentally. In the present article, we review our recent analysis of the two-photon dynamics in a cavity quantum electrodynamics (QED) system. Since a cavity-QED system is highly dispersive around its resonances, the shapes of photonic pulses are significantly deformed through interaction with the system. Thus, the present analysis is based on a formalism beyond single-mode approximations. The external photon field is treated rigorously as a continuum, which enables us to handle the two-photon wavefunction in the space representation. The degree of optical nonlinearity in a two-photon state is quantified by comparing the output wavefunction with the linear output wavefunction. It is revealed that the semiclassical optical response theory can be applied for evaluation of the two-photon optical nonlinearity. The two-photon nonlinearity appears not purely as a phase shift in the output wavefunction. The degradation of the fidelity between the output wavefunction and the linear output wavefunction always occurs, which hinders the application of this nonlinear effect as a quantum phase gate. The optimum condition for maximizing the two-photon nonlinearity is clarified, suggesting that pulse shape control is more essential than the Q-value control of the cavity QED system.

Study on resistive wall mode based on plasma response model

A uniform framework, based on the frequency dependent plasma response model (PRM), is proposed to study the physics and control of the resistive wall mode (RWM). The PRM is constructed, respectively, from the Fitzpatrick–Aydemir model, from a cylindrical theory with multiple RWM, and, finally, from toroidal calculations. Based on the PRM, several important aspects of the RWM physics are studied, including the interplay between active feedback and plasma rotation to stabilize the mode, the efficiency of external versus internal active coils for the mode control and the resonant field amplification effect due to a rotationally damped RWM.

NANOSCALE FIELD IONIZATION SENSORS: A REVIEW

So far, one of the most promising applications of nanoscale science and technology has been in the area of field emission. The electric field amplification effects associated with sharp nanostructure tips can be used to significantly reduce the emission voltages. Another equally promising area that also takes advantage of the field amplification effects is the area of field ionization. The extremely high electrical fields generated near the vicinity of sharp nanostructure tips can be used to ionize chemical or biological species at a fraction of the voltage of a traditional ionizer. In this article we review two of the very first reported papers related to nanoscale field ionization published by our group at the Rensselaer Polytechnic Institute. The first paper describes a carbon nanotube gas ionizer, which shows potential for gas sensing applications. The second paper describes an ultra low-power gas ionizer featuring β-phase Tungsten nanorod electrodes. We end with a review of the major challenges that must be overcome to develop nanoscale ionization sensors.