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We propose a thermal modulation structure made of two identical SiO2 slabs coated by Dirac semimetal (DSM) films and separated by a nanoscale vacuum gap. The energy transmission probability reveals...

Surface-enhanced Raman scattering (SERS) has been widely reported to improve the sensitivity of Raman spectra. Ordinarily, the laser is focused on the sample to measure the Raman spectrum. The size of the focused light spot is comparable with that of micro-nano structures, and the number of micro-nano structures contained in the light spot area (defined as duty cycle) will severely affect the spectrum intensity. In this study, flower-like silver nanostructures were fabricated with a soft lyotropic liquid crystal template in order to investigate the effect of duty cycle. They were observed under a scanning electron microscope, and their spectrum enhancement factor was computed with the obtained Raman spectrum. Then, their duty cycles were measured using a SERS substrate at different locations. A formula was derived to represent the relation between the duty cycle of the nanoflowers and the Raman spectral intensity. This work could promote the actual applications of SERS in high-sensitivity spectrum testing.

We propose a thermal modulation structure composed of two identical graphene-coated NaBr plates separated by a nanoscale vacuum gap (d). A static magnetic field perpendicular to the graphene sheet induces TE–TM hydrid surface plasmon polaritons between graphene and vacuum gap (called the hybrid GSPPs) and enhances the coupling of the hybrid surface plasmon polaritons in graphene to the surface phonon polaritons in the reststrahlen band of NaBr (called the coupled SPh–SPPs). The hybrid GSPPs and coupled SPh–SPPs play a key role in the thermal modulation. The heat flux is modulated by changing the static magnetic field, the Fermi level (EF) and carrier mobility (μ) in graphene. When the magnetic field varies from 0 to 30 T, the modulation contrast as high as 3.42, 3.25 and 4.48 is acquired at (d, EF, μ)=(60.64 nm, 0.2 eV, 1000 cm2/V · s), (100 nm, 0.21 eV, 1000 cm2/V · s) and (100 nm, 0.2 eV, 2500 cm2/V · s), respectively. The work opens new routes to magnetically modulate near-field radiative heat flux in graphene-based structures, and provides some guidance for applications in thermal management of nano/microscaled devices.

Tungsten (W) is used as the armor material of the International Thermonuclear Experimental Reactor (ITER) divertor and is regarded as the potential first wall material of future fusion reactors. One of the key challenges for the successful application of W in fusion devices is effective control of W at an extremely low concentration in plasma. Understanding and control of W erosion are not only a prerequisite for W impurity control, but also vital concerns to plasma-facing component (PFC) lifetime. Since the application of ITER-like water-cooled full W divertor in EAST in 2014, great efforts were made to investigate W erosion by experiment and simulation. A spectroscopic system was developed to provide a real-time measurement of W sputtering source. Both experiment and simulation results indicate that carbon (C) is the dominant impurity causing W sputtering in L-mode plasmas, which comes from the erosion of C plasma-facing material (PFM) in the lower divertor and the main chamber limiters. The mixture layer on the surface of W PFCs formed through redeposition or the wall coating can effectively suppress W erosion. Increasing the plasma density and radiation can reduce incident ion energy, thus alleviating W sputtering. In H-mode plasmas, control of edge localized mode (ELM) via resonant magnetic perturbation (RMP) proves to be capable of suppressing intra-ELM W erosion. The experiences and lessons from the EAST W divertor are beneficial to the design, manufacturing and operation of ITER and beyond.

Successful remediation of organics and heavy metals compound pollution is challenging, and their removal using conventional techniques is often difficult. This study developed an enhanced electrokinetics technology to decontaminate a hydrocarbon–heavy metal co-contaminated soil by applying biostimulation and selective membranes (cationic and anionic). A 30-day experiment was conducted in the laboratory to remediate the soil co-contaminated with total petroleum hydrocarbon (TPH) (9075 mg/kg) and Ni (446.6 mg/kg). The results demonstrated that the addition of anion- and cation-exchange membranes maintained soil pH stability. BioEK remediation under pH control improved microbial growth, microbial degradation of petroleum and reduced biological toxicity. Microbial action immobilized metals (e.g., reduction in exchangeable Ni and the increase in residual Ni). The degradation rate of TPH in contaminated soil was linearly correlated with the increase in TPH degradation population (P

We report a highly efficient thermal rectification model based on the near-field thermal radiation between InSb and graphene-coated SiO2, separated by nanoscale vacuum gaps. The results show that the introduction of graphene sheet enhances significantly near-field radiative heat flux and thermal rectification efficiency owing to the strong coupling of surface plasmon–polaritons between InSb and graphene. Specifically, under the same temperature bias, a rectification efficiency exceeding 80% is obtained at vacuum gaps varying from 10 nm to 100 nm for the graphene-coated SiO2 case, while such an efficiency requires a narrower gap between 10 nm to 20 nm for the bare SiO2 case. In addition, the introduction of graphene can lower greatly the emitter's temperature TH, e.g., an efficiency of 60% requires TH = 550 K in the bare SiO2 case, while it requires only the temperature around 400 K in the coated SiO2 case. The above results might be helpful in designing a highly efficient thermal diode with a wider vacuum gap and a lower operating temperature.

Eu3+, Tm3+ co-doped AlN thin films have been prepared through ion implantation for the first time. The implanted samples were annealed at 1180 °C in N2 to recover implantation damages and activate the rare-earth ions. Luminescence properties were investigated by photoluminescence and cathodoluminescence spectra. Under 325 nm laser excitation, for both Eu3+-doped AlN and Eu3+, Tm3+ co-doped AlN, the sharp characteristic emission lines corresponding to intra-4fn-shell transitions of Eu3+ were observed, but no any emission peak associated to Tm3+ ion was observed. According to the cathodoluminescence spectra, both Eu3+ and Tm3+ ions can be excited efficiently under high-energy electron beam. For Eu3+, Tm3+ co-doped AlN, the cathodoluminescence emission intensity of Eu3+ and Tm3+ ions varies with the dose ratio of these two ions. A possible energy transfer mechanism between Tm3+ and Eu3+ is proposed. Through changing the dose ratio of Eu3+ respect to Tm3+ ions, the chromaticity coordinates and color temperatures could be effectively regulated.

We propose a method for controlling the Imbert–Fedorov (IF) shifts of a reflected beam at a graphene-coated chiral metamaterial (CMM) interface, where graphene's chemical potential, the CMM's chirality parameter and the permittivity of dielectric at interface serve as external tunable stimuli to control the IF shifts. The spatial IF (SIF) shift and angular IF (AIF) shift are formulated by the reflection coefficients. The numerical results indicate that for p -polarized incident beam, the IF shifts can be controlled efficiently near the pseudo-Brewster angle through the chemical potential, and that both the high-permittivity dielectric and low-chirality CMM can bring about a broad shift modulation. Actually, the existence of graphene reduces the SIF shifts, but it can play a crucial role in the shift modulation. The above results might be helpful in exploiting various tunable terahertz-wave devices.

The deposited W layers formed on the W plate by hydrogen plasma sputtering were exposed to deuterium plasma in EAST together with bare W plate. In TDS measurement, the deuterium release was clearly observed from the deposited W layer in addition to the release of hydrogen which was incorporated during the sputtering-deposition processes. On the other hand, the release of hydrogen isotope was not detected from the bare W plate. This suggests that the formation of deposited W layers increases tritium inventory in the plasma confinement vessel. Although the thermocouple contacting to the backside of the W plate did not indicate a remarkable temperature rise, deuterium release peaks from the W layer were close to that from the W layer irradiated by 2keV D2+ at 573K. It was found by glow discharge optical emission spectrometry analysis that retained deuterium in the W layer has a peak at the depth of 50nm and gradually decreases toward the W substrate. From X-ray photoelectron spectroscopy analysis, it was evaluated that W oxide existed just at the surface and W atoms in the bulk of deposited W layer were not oxidized. These data suggest that hydrogen isotopes are not retained in W oxide but grain boundaries. Keywords: Deuterium retention, Deposited tungsten, EAST

Application of lithium (Li) or silicon (Si) wall coating in the Experimental Advanced Superconducting Tokamak (EAST) has proven to be an effective method to reduce fuel recycling and control impurity level, and also to improve the plasma performance. In 2014, the upper graphite divertor in EAST was upgraded into a full tungsten (W) one with ITER-like actively water-cooled monoblock structure. Note that there is still large surface area of first wall covered by graphite tiles, including the lower divertor, NBI shine through armor, the outboard guard limiters, etc. In 2016 spring campaign, both Li and Si were used to coat the first wall in experimental sequences that lasted more than one month each. The spectroscopic observation reveals that compared to Si coating, Li coating more effectively suppresses in-vessel impurities, thus mitigating the W source in upper divertor. This is further quantified by a reduction of the effective W sputtering yield calculation. Carbon (C) impurity is suggested as the main impurity governing W sputtering, and correlates inverselywith the wall coating evolution during both one-day experiments and the whole campaign. The impurity concentration increases measurably after every vacuum vessel exposure to air during the campaign; substantial time is required for impurities to return to baseline levels. Real-time Li aerosol injection into the upper divertor effectively reduces the W sputtering by cooling the edge plasma and dissipating the power flux to divertor target, consequently providing an active tool for radiation divertor control. Keywords: Lithium and silicon coating, Tungsten erosion, Impurity concentration, Spectroscopic diagnosis

To evaluate the effects of re-deposited tungsten (W) on the surface modification and hydrogen isotope retention behavior of fusion structural materials, the plasma exposure behavior of re-deposited W samples prepared by magnetron sputtering on the F82H steel, the V-5Cr-5Ti alloy as well as bare substrate samples was investigated. All the samples were exposed to 367 shots of deuterium plasmas in the 2015 spring EAST campaign. After the plasma exposure, large area of W layer was exfoliated, while big blisters were found at the interface between the remaining W layer and the substrate materials. The deuterium retention behavior of the samples with re-deposited W layer was characterized by thermal desorption spectroscopy and compared with the bare substrate samples.

Minority carrier lifetime and diffusion length are important parameters for GaN based material and devices. In this work, we obtained the minority carrier lifetime and diffusion length of p-GaN through the photoluminescence lifetime of the band edge peak, and analyzed the recombination behavior of carriers. Besides, the dependence of photoluminescence lifetime of GaN: Mg grown by MOCVD on annealing temperature (TA) and Mg concentration ([Mg]) has been investigated through Time-resolved Photoluminescence (TRPL) measurements. We increased the activated Mg acceptors ratio by increasing TA, analyzed the fast and slow decay of carrier recombination, and compared the effects of annealing on the lifetime of GaN band-edge emission with different Mg concentrations. And it is found that the minority carrier lifetime in p-GaN is not only related to Mg concentration, but also related to the activated Mg acceptors concentration / hole concentration. Meanwhile, we compared heteroepitaxial p-GaN with homoepitaxial p-GaN, and further analyzed the influence of dislocation as non-radiative recombination centers (NRCs) on carrier lifetime and recombination behavior.

The adaptive optics system (AOS) has been used to eliminate the effect of atmospheric turbulence for free-space optical communications. The AOSs are designed based on the statistical average performance of the turbulence. In reality, the amplitude of turbulence changes drastically, and the AOS cannot always detect and correct the aberrations appropriately. To prevent the amplitude of turbulence from exceeding the designed range of the Shack–Hartmann wavefront sensor (SH WFS), the combination of the wavefront sensorless and SH WFS methods is proposed to extend the detection range. First, the control scheme is demonstrated, and the numerical simulation is performed. Then, the validation experiments are performed with static and dynamic turbulence. Results show that the proposed method is valid and that the effective communication time is greatly lengthened.

Molten salt electrodeposition is a promising technology to manufacture the first wall of a fusion reactor. Deuterium (D) retention behavior in molten salt electrodeposition tungsten (W) coatings has been investigated by D-plasma exposure in the EAST tokamak and D-ion implantation in an ion beam facility. Tokamak exposure experiments demonstrate that coatings prepared with lower current density exhibit less D retention and milder surface damage. Deuterium-ion implantation experiments indicate the D retention in the molten salt electrodeposition W is less than that in vacuum plasma spraying W and polycrystalline W.

The ITER-like tungsten divertor with toroidally symmetric 1 mm × 1 mm chamfers on monoblock tiles has been installed in EAST in 2014. Hot spots were experimentally observed mostly along the toridial facing gaps between two columns of W/Cu monoblock units, which are often aggravated by installation misalignment. These hot spots can significantly degrade the power handling capability of W divertor and need to be alleviated. A numerical optimization model for tile chamfering design is built based on the finite element method (FEM), in which the numerical experiments are designed by the uniform table. The calculation results in ANSYS for these experiments are then processed employing the code Design and Analysis of Computer Experiments (DACE) in which the Kriging method is adopted to reconstruct a response surface. The optimum geometry can be derived from the minimum point on the surface. The results show that, under 200 MW/m2 parallel heat flux with an inclination angle of 3° with respect to tile surface, the maximum temperature on W tile with a 0.5 mm misalignment can be decreased to 2084 °C by adopting an optimized single-sided chamfer, 1.8 times lower than 1 mm × 1 mm symmetrically chamfered tile. The optimum chamfering geometry has a strong dependence on the inclination angle of plasma flux to tile surface. As a result, the monoblock tiles in a flat cassette module need to be chamfered differently to adapt to the varied inclination angles.

We propose a thermal modulation structure composed of two identical Weyl semimetal (WSM) slabs separated by a nanoscale vacuum gap. Following Maxwell's equations and the dielectric tensor of the WSM, we derive the reflection matrix at the WSM/vacuum interface. Based on fluctuation electrodynamics, the effects of the Fermi level, the number of Weyl nodes, the separation between Weyl nodes and the thickness of vacuum gap on the heat transfer coefficient and the thermal modulation contrast are numerically discussed. It is found that the WSM possesses stronger near-field radiative ability in the low frequency region, where the coupled surface plasmon polaritons between the WSM slabs play a dominant role. By continuously tuning the Fermi level from 0.01 to 0.15 eV, a large modulation contrast as high as 58.5 is obtained at T = 300 K, while in the low temperature interval [ 50 ,160] K, the minimum modulation contrast can exceed 198 for a vacuum gap of 20 nm. The obtained results might be helpful in designing a WSM-based thermal modulator with giant modulation contrasts.

We suggest a thermal rectification structure where a semi-infinite InSb plate and a semi-infinite 3C–SiC plate coated by black phosphorus (BP) sheets are separated by a nanoscale vacuum gap. To obtain high and tunable thermal rectification efficiency, we employ the temperature-dependent dielectric properties of both InSb and 3C–SiC, and introduce BP sheets with in-plane anisotropy into the structure. Based on fluctuational electrodynamics, the near-field radiative heat transfer and the rectification efficiency are calculated. It is found that the rectification efficiency varies very sensitively with the emitter's temperature, the chemical potential and the number of BP layers, thus opening up possibilities to control the rectification efficiency through these parameters. Higher rectification efficiencies are obtained under some certain conditions, and the origins of the thermal rectification effect are elucidated in some detail. The obtained results might be helpful in designing a BP-based high-efficiency thermal diode.

In view of the uncertainty of ranging and direction angle in the ultrasonic sensor measurement, an ultrasonic distance detection model based on uncertainty region is first of all proposed through analyzing the working principle of the ultrasonic sensor. Moreover, the DSmT method is adopted to fuse the uncertainty data measured by using the ultrasonic sensor. Next, the Hough Transform and the least-square method are combined to estimate environmental contour. Finally, an indoor environment is measured and built by using the ultrasonic sensor hardware system for experimental verification. The environmental contour obtained in the experimental results is consistent with the real environment, which illustrates the feasibility and effectiveness of the proposed method. This proposed method has certain reference value for the research of the environmental mapping and positioning of the mobile robot.

Cu–Li–Cu multilayers were deposited on Si substrate by alternately using magnetron sputtering and resistance evaporation. Scanning Electron Microscope (SEM) and Rutherford Backscattering Spectrometry (RBS) were utilized to study the interaction and diffusion between Cu and Li after 8 h heat treatments at 100, 280, and 480 °C. The RBS results reveal that Li can diffuse into Cu when the temperature rises to 480 °C. As a supplementary experiment on Cu corrosion by Li at lower temperature, bulk Li and Cu were annealed at 240, 320 and 400 °C for 8 h separately in a high-temperature furnace after sealing in quartz ampoules. Morphology images show that Li corrodes grain boundaries of Cu preferentially when the temperature is higher than the melting point of Li, and the corrosion rates are 0.7875, 0.925 and 3.3275 mg/h, respectively. The results are helpful for understanding the Cu corrosion and protecting the Cu components in EAST.

We study for the first time the transverse shifts of a Gaussian beam reflected from a uniaxially anisotropic chiral (UAC) slab, where the chirality appears only in one direction and the host medium is a uniaxial crystal or an electric plasma. The results indicate that the transverse shifts are closely related to the propagation behaviors of the eigenwaves in the slab. Specifically, when one or both of the eigenwaves are totally reflected at the second interface of the slab, the spatial transverse shift becomes resonances but is not enhanced; when one eigenwave is totally reflected at the first interface and the other is transmitted at the second interface, the larger and negative transverse shifts can be obtained. The propagation behaviors of the eigenwaves in the UAC slab provide more abundant information about the transverse shifts than in a single interface structure.

To facilitate long-pulse high power operation, an ITER-like actively cooled tungsten (W) divertor was installed in Experimental Advanced Superconducting Tokamak (EAST) to replace the original upper graphite divertor in 2014. A dedicated multichannel visible spectroscopic diagnostic system has been accordingly developed for the characterization of the plasma and impurities in the W divertor. An array of 22 lines-of-sight (LOSs) provides a profile measurement of the light emitted from the plasma along upper outer divertor, and the other 17 vertical LOSs view the upper inner divertor, achieving a 13 mm poloidal resolution in both regions. The light emitted from the plasma is collected by a specially designed optical lens assembly and then transferred to a Czerny-Turner spectrometer via 40 m quartz fibers. At the end, the spectra dispersed by the spectrometer are recorded with an Electron-Multiplying Charge Coupled Device (EMCCD). The optical throughput and quantum efficiency of the system are optimized in the wavelength range 350-700 nm. The spectral resolution/coverage can be adjusted from 0.01 nm/3 nm to 0.41 nm/140 nm by switching the grating with suitable groove density. The frame rate depends on the setting of LOS number in EMCCD and can reach nearly 2 kHz for single LOS detection. The light collected by the front optical lens can also be divided and partly transferred to a photomultiplier tube array with specified bandpass filter, which can provide faster sampling rates by up to 200 kHz. The spectroscopic diagnostic is routinely operated in EAST discharges with absolute optical calibrations applied before and after each campaign, monitoring photon fluxes from impurities and H recycling in the upper divertor. This paper presents the technical details of the diagnostic and typical measurements during EAST discharges.

The Material and Plasma Evaluation System (MAPES) in the EAST tokamak has been built up and used to address a variety of plasma–material interaction (PMI) issues relevant to ITER in 2012 EAST campaign. The topics studied cover erosion/redeposition of plasma-facing materials and components, hydrogenic retention in the gaps of castellation structure, deterioration of diagnostic mirrors from impurity deposition and protective technique. An introduction of MAPES system and an overview of the recent experimental results are presented.

1.5at% Eu-doped GaN powders were prepared by a co-precipitation method. Powder X-ray diffraction (XRD) results shows that there is only the wurtzite phase. Cathodoluminescence spectra were measured at room temperature and liquid nitrogen temperature, respectively. The band-to-band luminescence of GaN was shifted from 373 nm to 368 nm with the temperature decreasing from room temperature to liquid nitrogen temperature. The luminescence peaks at 537, 557, 579, 590, 597, 614, 653 and 701 nm are attributed to the Eu ions related transitions in the host of GaN powders and the peak positions were not influenced by the variation of temperature. With the increase of accelerating voltage, the intensity of all luminescence peaks was increased. The strongest luminescence peak at 614 nm shows non-symmetrical shape and is composed of 612, 615 and 621 nm through Lorentzian fitting, which indicates there are oxygen and nitrogen environments of the Eu3+ ions in the Eu-doped GaN powders.

We investigate the Goos–Hanchen (GH) shifts of reflected light from Kerr-like slabs, whose permittivities are inhomogeneous in space as well as light intensity dependent. The GH shifts exhibit bistable, multivalued properties or a more complicated hysteretic response to the input light intensity, and the different spatial dependences of the permittivity have a great effect on the hysteretic response. The bistable or multivalued GH shifts can be modulated by various parameters, such as the angle of incidence and the thickness of slab.

We study the Imbert–Fedorov (IF) shifts of a reflected Gaussian beam from uniaxially anisotropic chiral media (UACM), where the chirality appears only in one direction and the host medium is a uniaxial crystal or an electric plasma. The numerical results are presented for three kinds of UACM, respectively. It is found that the IF shifts are closely related to the propagation properties of the two eigenwaves in the UACM. In general, when either of the eigenwaves is totally reflected, the IF shifts can change abruptly near the critical angle. The cross-polarized reflection coefficient has a greater effect on the spatial IF (SIF) shift than on the angular IF (AIF) shift, and the sign of the AIF shift depends mainly on that of the difference between the co-polarized reflectivity. By designing artificially the electromagnetic parameters of the UACM, we can control the IF shifts and acquire their more abundant properties.

Based on the invariant imbedding method and stationary phase approximation, we perform a theoretical investigation on the lateral shifts through an inhomogeneous medium, whose permittivity and permeability are sine functions of the thickness. We find the lateral shift is large near the angles of transmissivity resonances. Furthermore, using a numerical solution method, we discuss the dependence of lateral shift on the spatial period of permittivity, the angle of incidence, the slab's thickness and the signs of the permittivity and permeability, respectively. The results show that the angles of transmissivity resonance and the lateral shifts can be easily controlled by adjusting the parameters of the structure.

A laser based method combined with spectroscopy, such as laser-induced breakdown spectroscopy (LIBS) and laser-induced ablation spectroscopy (LIAS), is a promising technology for plasma-wall interaction studies. In this work, we report the development of in situ laser-based diagnostics (LIBS and LIAS) for the assessment of static and dynamic fuel retention on the first wall without removing the tiles between and during plasma discharges in the Experimental Advanced Superconducting Tokamak (EAST). The fuel retention on the first wall was measured after different wall conditioning methods and daily plasma discharges by in situ LIBS. The result indicates that the LIBS can be a useful tool to predict the wall condition in EAST. With the successful commissioning of a refined timing system for LIAS, an in situ approach to investigate fuel retention is proposed.

We study the Imbert–Fedorov (IF) shifts of a reflected Gaussian beam from anisotropic topological insulators (TIs). Aiming, respectively, at the two types of TI surface perturbations that can alter the surface optical properties, i.e., a magnetic coating and an applied magnetic field, we discuss the dependences of the IF shifts on the axion field, the TI's extent of anisotropy, the angle of incidence and the applied magnetic field. For a left-elliptically polarized incident beam, a positive (negative) axion field can lead to the decrease (increase) of the IF shifts relative to a conventional insulator in the magnetic coating case, and in the applied magnetic field case, the crossover of the IF shifts between the positive and the negative values can be realized by adjusting some external parameters. Also, the properties of the IF shifts are discussed for linearly and circularly-polarized incident beams. The results show that TI might be a desirable candidate for controlling flexibly the IF shifts.

Goos–Hanchen (GH) shifts of the reflected waves through a transition layer where both the dielectric permittivity e and magnetic permeability µ change linearly from positive to negative values are investigated. Based on invariant imbedding approach and the stationary-phase method, the differential equations for the reflection and transmission coefficients are obtained. We demonstrate numerically the dependence of the shifts on the angle of incidence and the inhomogeneous slab's thickness. The results show that the GH shifts are sensitive to the angle of incidence in a specific thickness. Different thickness of media can result in the different dependences of the shifts on the angle of incidence. At the positions where e or µ is zero, due to the resonant effect, the GH shifts can be greatly enhanced.

We obtain the repulsive Casimir force between two parallel gyroelectric slabs, thus overcoming the difficulty that the repulsive Casimir force is difficult to achieve in a naturally occurring material. Under practically realizable parameters, we realize the crossover from attractive (repulsive) to repulsive (attractive) forces by changing either the external static magnetic field, the background permittivity of the gyroelectric medium, the slab’s thickness or the gap between the slabs. The proposed configuration, unlike the artificial metamaterial one, does not require the careful design of the material’s micro-structure, and hence is expected to be a practical candidate for obtaining a repulsive Casimir force.

We propose a thermal rectification structure composed of InSb and graphene-coated 3C-SiC separated by a nanoscale vacuum gap. To obtain an obvious thermal rectification effect, the permittivities of these materials are all considered to be temperature-dependent. Numerical calculations based on fluctuation electrodynamics reveal that the introduction of graphene into the structure enhances significantly near-field radiative heat flux and thermal rectification efficiency owing to the strong coupling of surface plasmon-polaritons between InSb and graphene. In general, the rectification efficiency above 60% can be maintained for the vacuum gap less than 70 nm. The rectification efficiency exceeding 95% is realized for a vacuum gap of 10 nm and a chemical potential of 0.1 eV. Increasing the emitter’s temperature leads to the drastic increase of the rectification efficiency in a wider temperature range. A lower chemical potential seems more favorable to raising rapidly the rectification efficiency. The above results might be helpful in designing a thermal diode with higher efficiency and wider vacuum gap.

We present a study of the optical propagation properties of one-dimensional (1D) MoS2/metal photonic crystals (PCs) formed by periodic stacking of alternating MoS2 and metal layers in ambient air atmosphere. The propagation properties of light moving in such a structure are solved using the transfer matrix method. The optical properties of the MoS2/metal PCs are obtained analytically as a function of the materials used, the thicknesses of the layers, and the number of units. Among Ag, Al, Ni, and Fe, Ag was the most suitable metal for constructing PCs in the visible light range. The transmission spectra of the MoS2/Ag PCs exhibited periodic oscillation, with 1, 2 photonic band gaps (PBGs) in the 400–800 nm range when the thickness of the Ag film was 1–2 nm, and the optimum number of periodic units, N, was 10-20. Beyond this range, the transmittance of the structures monotonically decreased with increasing wavelength. The periodic oscillation properties of transmittance in MoS2/Ag 1D PCs can be used in sensors and detectors and as real-time monitors for biological and medical technology fields.

In this paper, we will experimentally investigate the power threshold (PL-H) in upper single null plasmas with an ITER-like tungsten divertor under different ∇B drift directions on EAST [F. Ding et al., Commissioning and PSI Behavior of the ITER-Like W/Cu Divertor in EAST 22nd PSI, Rome (2016)]. The power threshold for the low (L) to high (H) confinement mode has a clear and positive toroidal magnetic field, BT, dependence when the ∇ B drift points toward the primary X-point (Bx∇B↑). A factor of 2-3 increase in PL-H is observed for the ∇B drift away from the primary X-point (Bx∇B↓). The edge and core impurities quantified by spectroscopy measurements show comparable levels for the transitions for both drift directions. On the other hand, it is found that the divertor Dα emission just prior to the L-H transition is lower for Bx∇B↑, compared with that for Bx∇B↓. The upper in-out divertor asymmetry, as manifested by particle fluxes measured by the divertor triple Langmuir probe, is most marked for Bx∇B↓, and with significantly more particle flux to the outer divertor. The reversing field increases the particle flux into the upper inner and lower outer divertor, reducing the in-out asymmetry. One important distinction between the two field directions has been observed, with respect to the amplitude of the scrape-off layer (SOL) parallel flow. A dedicated experiment under similar target plasma conditions shows a lower SOL density and thus a steeper density gradient slightly inside the separatrix, where a lower PL-H is found for the Bx∇B↑, compared to that for Bx∇B↓. We, therefore, conclude that the fielddependent SOL plasma conditions play an important role in the transition physics.

As the surface polaritons are excited in Kretschmann configuration with a Kerr-type substrate, the nonlinear Goos–Hanchen (GH) shifts exhibit the optically hysteretic response to the intensity of incident light. For thicker metal films, the GH shifts become very sensitive to the intensity of incident light and the angle of incidence.

The optical properties of the Au–Ag alloy nanowire coated with a cylindrical shell with radial dielectric anisotropy are investigated based on quasistatic theory. Numerical results show that the surface plasmon resonance (SPR) peak is redshifted with increasing the component ratio of Au in the alloy, while the intensity of extinction section at the SPR increases with increasing the component ratio of Ag in the alloy. In addition, as the extent of anisotropy of the shell increases, the extinction section at SPR wavelength decreases and the SPR wavelength is redshifted, but compared with the isotropic shell consisting of comparable dielectric constant materials, the SPR has a distinct blueshift for anisotropic shell. We also find that the field enhancement can be completely concentrated inside the anisotropic shell and the electromagnetic transparency can be exhibited.

We investigate the spectra and scintillation properties of Ce:YAlO3, Ce:Y3Al5O12, and Ce:LaAlO3. For Ce:YAlO3, the excitation spectrum is very similar with the absorption spectrum; for Ce:Y3Al5O12 and Ce:LaAlO3, the excitation spectra are different from the absorption spectra. Further, Ce:YAlO3 has better scintillation performance than Ce:Y3Al5O12; whereas Ce:LaAlO3 has not demonstrated scintillation performance to date. We also provide reasonable explanations for these experimental phenomena from the viewpoint of energy level structure.

Tungsten erosion and re-deposition at the upper outer divertor of the Experimental Advanced Superconducting Tokamak has been modelled using the 3D Monte Carlo code ERO. The measured divertor plasma condition in attached L mode discharges with upper single null configuration has been used to build the background plasma in the simulations. The tungsten gross erosion rate is mainly determined by carbon impurity in the background plasma. Increasing carbon concentration can first increase and afterwards suppress the tungsten erosion rate. Taking into account the material mixing surface model, the influence of eroded particles returning to the surface on sputtering has been studied. Sputtering by eroded particles returning to the surface can significantly enhance the gross erosion by reduction of the carbon ratio within the surface interaction layer and by increasing the erosion rate due to sputtering by both eroded tungsten and carbon particles. Modelling indicates that carbon deposition occurs on the dome pla...

To investigate the radiative divertor behavior and physics for the scenario of impurity seeded plasma in ITER, the radiative divertor experiments with argon (Ar) seeding under ITER-like tungsten divertor condition were carried out during recent EAST campaigns. The experimental results reveal the high efficiency of reducing heat load and particle flux onto the divertor targets owing to increased radiation by Ar seeding. We achieve detached plasmas in these experiments. The inner–outer divertor asymmetry reduces after Ar seeding. Impurities, such as Ar, C, Li, and W, exist in the entire space of the vacuum chamber during EAST operations, and play important roles in power exhausting and accelerating the plasma detachment process. It is remarkable that the contamination of the core plasma is observed using Ar seeding owing to the sputtering of plasma facing components (PFCs), particularly when Ar impurity is injected from the upper tungsten divertor.

Based on a general beam-propagation model, we derive in the paraxial approximation the analytical expressions for the spatial transverse shift (TS) and the angular TS of a beam reflected from the air-chiral interface. The results show that the TSs are closely related to the propagation behaviors of the right-circularly polarized (RCP) and the left-circularly polarized (LCP) waves in the chiral medium. When the L(R)CP wave becomes evanescent, the left (right)-elliptically polarized incident beam suffers a smaller TS. When the L(R)CP wave propagates, the left (right)-elliptically polarized incident beam experiences a greater TS. When the total internal reflection happens, neither of the two elliptically polarized incident beams suffers TSs. TSs can be controlled not only by adjusting the central angle of incidence, but also by tailoring the permittivity, permeability, and chirality parameter of the chiral medium.

Er ions are implanted into the GaN thick films grown by hydride vapor phase epitaxy. The implantation energy is 200 keV and the implantation doses are 1×1013, 1×1014, 1×1015, and 5×1015 atom/cm2, respectively. The effects of the implantation dose and annealing temperature on the GaN band-edge luminescence are investigated. The cathodoluminescence spectra from 82 to 323 K are measured for 1×1015 atom/cm2-implanted GaN annealed at 1100°C. Luminescence peaks at 356, 362, 376, 390, and 414 nm are observed on the 82 K cathodoluminescence spectrum. When the temperature is increased to 150 K, the intensities of the 356 and 414 nm peaks are nearly unchanged and the 362, 376, and 390 nm peaks disappear. The intensity ratio of 538 nm (H11/22→I15/24) and 559 nm (S3/24→I15/24) is increased with the increase in temperature. We try to shed light on the above interesting phenomena.