Three-wave interactions between fast-ion modes in the National Spherical Torus Experiment

Simultaneous bursts of energetic particle mode (EPM) and toroidicity-induced Alfvén eigenmode (TAE) activity that correlate with significant fast-ion loss are observed in beam heated plasmas. Three-wave interactions between these modes are conclusively identified, indicating fixed phase relationships. This nonlinear coupling concentrates the energy of the TAEs into a toroidally localized perturbation frozen in the frame of a rigid, toroidally rotating structure formed by the EPMs. This redistribution of energy is significant because it will modify the effect of the TAEs on fast-ion loss.     

Momentum-transport studies in high E x B shear plasmas in the National Spherical Torus Experiment

Experiments have been conducted at the National Sperical Torus Experiment (NSTX) to study both steady state and perturbative momentum transport. These studies are unique in their parameter space under investigation, where the low aspect ratio of NSTX results in rapid plasma rotation with ExB shearing rates high enough to suppress low-k turbulence. In some cases, the ratio of momentum to energy confinement time is found to exceed five. Momentum pinch velocities of order 10-40 m/s are inferred from the measured angular momentum flux evolution after nonresonant magnetic perturbations are applied to brake the plasma.     

Numerical simulation of fueling pellet ablation and transport in the EAST H-mode discharge

To understand the effect of injected deuterium (D) pellets on background plasma, the ablation of D pellets and the transport of D species in both atomic and ionic states in the EAST device are simulated using a modified dynamic neutral gas shield model combined with the edge plasma code SOLPS-ITER. The simulation results show that there is a phenomenon of obvious atomic deposition in the scrape-off layer (SOL) after pellet injection, which depends strongly on the injection velocity. With increasing injection velocity, the atomic density in the SOL decreases evidently and the deposition time is relatively shortened. Possible effects for triggering of edge localized modes (ELMs) by D and Li pellets are also discussed. With the same pellet size and injection velocity, the maximum perturbation pressure caused by D pellets is obviously higher. It is found that the resulting maximum perturbed pressure is remarkably enhanced when the injection velocity is reduced from 300 m/s to 100 m/s for a pellet with a cross section of 1.6 mm, which indicates that the injection velocity is important for ELM pacing. This work can provide reasonable guidance for choosing pellet parameters for fueling and ELM triggering.     

Excitation of the Rydberg states of lithium in a hollow-cathode discharge

Excited states of lithium are populated in a transverse hollow-cathode discharge (HCD) working in helium-lithium mixture. Excited state population is controlled through the HCD voltage by the high-energy electrons. This excitation is distributed among the different levels by collisions with neutral atoms and low-energy electrons. The measured excitation temperatures reflect these redistribution processes.     

Surface cleaning effect of NCM powder and improvement of lithium ion battery on the thermal stability and life cycle employing dielectric barrier discharge technique

Mixed NCM (nikel, cobalt, and manganese) powder was treated by a reactive gas from dielectric barrier discharge (DBD) to prepare a cathode material in Lithium ion (Li-ion) battery. The DBD was mainly sustained using N₂ gas at atmospheric pressure, and NF₃, SF₆, and H₂ was fed into the discharge to create the reactive gas. Compare to the non-treated sample, impurities on the surface of the NCM powder were significantly removed in a 5 min when the reactive gas was blow into the powder and mixed properly. F atom content on the surface was increased depending on the time duration of mixing, which form a LiF layer on the surface. Desirable LiF layer suppress a heat flow effectively , resulting a decreasing of exothermic temperature inside the Li-ion battery. Additionally, the treatment of NCM powder employing DBD technique was also contributed to electrochemical performance, which was confirmed by c-rate testing.     

民族师范本科院校大学物理实验教学改革的实践与构想

指出当前大学物理实验教学中存在的问题的同时,对实验教学方法的改革问题进行了分析探讨,以此提高实验教学水平和培养创新人才。     

The evaluation of the performance of two pyroelectric detectors with vertically aligned multi-walled carbon nanotube coatings

Two LiTaO₃ pyroelectric detectors coated with vertically aligned multi walled carbon nanotube (MWCNT) black coatings were assembled and evaluated using NPL’s detector characterisation facilities. The vertically-aligned nanotube array (VANTA) black coatings were grown on a silicon substrate and subsequently lifted off the silicon and bonded on the pyroelectric crystal substrates. Despite some drawbacks, this method was shown to provide a reliable way of coating delicate substrates such as pyroelectric crystals with VANTA coatings. The performance of the coated and uncoated detectors was evaluated and compared by coating only half of the active area of the test detectors, leaving the other half uncoated. The relative spectral responsivity of the VANTA-coated pyroelectric detectors was shown to be spectrally flat in the 0.8–14 μm wavelength range within the uncertainty of the measurements. The spatial uniformity of response of both detectors exhibited fine structure which was assigned either to the thickness of the VANTA coatings or to their bonding to the pyroelectric crystal. Both coated and uncoated detectors exhibited a super-linear response. This observation was expected in the case of the uncoated detectors, but was surprising in the case of the coated detectors and indicates that the thermal conductivity of vertically aligned multi-walled carbon nanotubes is high along their long axis. The spatial variations of the phase delay experienced by the signal propagating through the VANTA coatings indicate that the thermal diffusivity of the coatings is not spatially uniform.     

Nanostructuring of the submonolayer carbon coatings deposited onto the surface of silicon single crystals in a low-pressure microwave discharge plasma

The surface nanostructuring of the submonolayer carbon coatings deposited onto (111) and (100) silicon wafers in a highly ionized ultrahigh-frequency low-pressure plasma is studied. The effect of the coating thickness and the main processing parameters on the mechanisms of morphological changes is studied with allowance for the reconstruction of a single-crystal silicon surface and the mechanical stresses that appear during the preparation of an atomically clean surface during plasma-chemical etching, heterogeneous condensation, and high-temperature annealing. Integral columnar nanosystems with a density of (4?C5) × 10⁹ cm^?2 and a height of 400 nm are formed on (100) silicon single crystals using nanostructured carbon aggregates as mask coatings and highly anisotropic plasma-chemical etching.     

第一性原理计算研究黑磷嵌锂态的动力学性能

采用基于密度泛函理论的第一性原理方法对锂离子电池负极材料黑磷在嵌锂过程中的产物LiP5,Li3P7以及LiP的晶体结构与电子结构进行了研究与分析．通过计算这几种材料的电子结构,发现黑磷嵌锂后的这几种相均为半导体能带结构,其带隙均比黑磷嵌锂前的带隙大,表明黑磷嵌锂后的电子电导性能降低了．利用弹性能带方法模拟了Li离子在LiP5,Li3P7和LiP材料中的扩散,从理论上得到了Li离子的扩散势垒,并与其他电极材料进行了比较,发现Li离子在各种嵌锂态的材料中都能够比较快速的扩散．计算结果表明,Li在LiP5中的扩散系数大约为10^-4cm2／s,扩散通道是一维的;Li在Li3P7中的扩散系数为10^-7-10^-6cm2／s,扩散通道是三维的;Li在LiP中的扩散系数为10^-8-10^-5cm2／s,扩散通道是三维的．     

Estimation of the performance of a 3-dB Y-junction optical coupler with a channel profile of proton-exchanged lithium niobate

A 3-dB optical coupler (power splitter) based on a Y-junction waveguide with a channel profile of proton-exchanged lithium niobate has been modeled. Finite difference beam propagation method has been used to investigate light wave propagation in axially varying waveguides. It is found that the structure splits the input power equally at the Y-junction with an efficiency of 99% and an average excess loss ?0.04 dB. The novelty of the coupling structure proposed is its capability to function as a wavelength-independent 3-dB coupler while maintaining very low-power imbalance for widespread optical communication wavelengths of 1.3 and 1.55 µm.     

Interaction of fullerenes with metallic lithium in the condensed state

The relative stability of exo-and endohedral lithium complexes with the C₆₀ fullerene was estimated using quantum chemistry and molecular-dynamics methods. Endohedral compounds were shown to have a higher stability. The possible maximum filling of the C₆₀ inner sphere by lithium was estimated theoretically. The interaction of metallic lithium with the C₆₀ fullerene and a C₆₀ + C₇₀ mixture was studied using DTA and EPR and established to proceed in several stages.     

Enhanced electrochemical performance of lithium vanadium phosphate as cathode by LiBOB/LiTFSI with additive in EC/EMC

A series of Li₃V₂(PO₄)₃/C (LVP/C) samples with monoclinic structure indexed to P2₁/n space group were synthesized using V₂O₃ as vanadium source by solid state reaction method by different sintering temperatures. It was found that the LVP/C sintered at 750 °C with a carbon content 3 wt.% was the optimum condition for this synthesis. The structural, morphological, superficial, and textural properties of LVP/C were characterized by XRD, SEM, TEM, and XPS. The electrochemical performance was evaluated by galvanostatic charge–discharge cycling using new high voltage electrolyte. The optimized cell delivered an initial discharge capacity of 187 mAh g^?1 in the higher cut-off voltage of 3.0–4.8 V vs. Li⁺/Li⁰ at 0.2 C rate, with a capacity retention of 88 %, 89 %, and 61 % after 50 cycles discharging at 1 C, 2 C, and 4 C, respectively. The capacity can be almost recovered at 0.5 C after long cycles. The excellent stability is contributed to the new high-voltage electrolyte.     

Electrochemical performance of the (Ni, Cr) doped spinel material as cathode in lithium cells

The (Ni:Cr) doped lithiated manganese oxide electrode is prepared by wet chemical route using citric acid as the precursor material. The various physical and chemical properties of the prepared electrode material were studied by DSC, XRD, FTIR, Raman and SEM measurements. The electrical conducting property of the electrode was studied by the d.c. conductivity measurements. The electrochemical property was also evaluated by using test cells with the (Ni:Cr) doped spinel electrode. The cycle life was found to be increased upon increasing dopant concentration. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

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介绍了HL-2A装置会切场桶式离子源在实验平台运行时某些放电参数的变化对离子源放电特性的影响。分析并讨论了产生这些现象的原因。这对于提高源的可靠性和稳定性,提高饱和离子流密度,增大引出电流和提高弧效率有一定的指导作用。     

上海天文台近年来氢脉泽的技术改进与性能评价

氢脉泽具有优秀的中长期频率稳定度,由于环境温度的变化及谐振腔老 化会引起谐振腔频率的变化,导致氢脉泽长期性能降低。通过采用自动调谐器可确保谐振腔 的频率始终工作在所需的频率上,从而改善了氢脉泽的长期性能,日稳定度可达到1.0～10 -14。这篇文章描述了上海天文台研制的氢脉泽的技术改造与性能。     

Study of the glow discharge in inert gases with water vapor

The behavior of the water vapor concentrations and fragments in wet plasma is studied. The results of plasma-chemical modeling are compared with the results of direct measurements of water molecule dissociation in plasma.     

Surface modification of lithium deuteride single crystals in interaction with the atmosphere

Interactions between the surface of lithium deuteride and atmosphere at room temperature are studied by Rutherford backscattering spectroscopy and recoil nuclei.     

Investigation of the output characteristics of a He−Ne laser with transverse UHF discharge in a long discharge tube

Tashkent State University, Department of Physics, TashSU, Vuzgorodok, Tashkent, 700095 Uzbekistan. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 63, No. 6, pp. 974–976, November–December, 1996.     

Oxidation state of vanadium in amorphous MnV2O6 formed during discharge–charge cycle and the improvement of its synthesis condition

Crystalline powders of anhydrous MnV₂O₆ were successfully synthesized at a temperature below 200 °C under autogenous hydrothermal condition. MnV₂O₆ powders, which were synthesized using high concentration solutions, more than 0.1 mol/L, gave a relatively high reversible capacity of 600 mA h/g and interesting cyclic performance, reversible capacity increasing to more than an initial charge capacity after the 3rd or 4th cycle of charge–discharge. The change in oxidation state of V ion on the course of the 1st discharge–charge process was investigated by different techniques, such as XAFS and XPS. During discharging, V⁵⁺ was found to change gradually to V⁴⁺, but it returned back completely to V⁵⁺ on charging process. The thinner particles of MnV₂O₆ crystals with rod-like morphology were synthesized at 135 °C, and much better anodic performance was achieved, much smaller irreversible capacity as about 300 mA h/g, stable reversible capacity as 600 mA h/g, and 100% Coulombic efficiency.