Evolution of lower-hybrid-driven current during the formation of an internal transport barrier

Evolution of the lower-hybrid(LH)-driven current profile was measured during the formation of an internal transport barrier (ITB) in a reversed magnetic shear discharge. As the ITB developed, the initially centrally peaked LH-driven current profile gradually turned hollow and was sometimes accompanied by an off-axis peak in the electron temperature profile. These observations indicate the concentration of LH power deposition to the ITB for this case as a result of nonlinear coupling between the LH waves and the target plasma.     

HL-2A装置的LHCD运行区域与驱动电流分布控制

讨论了低杂波电流驱动（LHCD）实验中电流驱动效率、电流分布控制与等离子体参数和入射波谱的关系,以及波的可近性对确定功率沉积分布的作用。讨论了控制电流密度分布的方法及在HL－2A装置上实现中心负剪切位形的可能性。     

Investigation of lower hybrid current drive during H-mode in EAST tokamak

H-mode discharges with lower hybrid current drive (LHCD) alone are achieved in EAST divertor plasma over a wide parameter range. These H-mode discharges are characterized by a sudden drop in D_α emission and a spontaneous rise in main plasma density. Good lower hybrid (LH) coupling during H-mode is obtained by putting the plasma close to the antenna and by injecting D₂ gas from a pipe near the grill mouse. The analysis of lower hybrid current drive properties shows that the LH deposition profile shifts off axis during H-mode, and current drive (CD) efficiency decreases due to the increase in density. Modeling results of H-mode discharges with a general ray tracing code GENRAY are reported.     

On the Nonlinear Processes During Generation of Current Drive

The manifestations of the induced scattering effects in the generation process of current driven by lower-hybrid (LH) waves are studied taking into account the radiative-resonant interactions. The influence extent of the LH wave modulational instability on current drive is estimated. It is shown that the induced scattering of LH waves on plasma particles leads to a change of the LH waves spectrum and through this leads to an essential influence on fast electrons generation rate and the steady-state current drive. The modulational instability of LH waves can provide a “spectral gap” filling in the case of sufficiently strong LH wave pumping.     

Semiquantitative estimates of currents generated by monochromatic waves in toroidal plasmas

Landau damping and transit time damping are analyzed from the point of view of toroidal electric current generation. Steady current density and energy absorption are estimated. The importance of momentum transfer to non-resonant electrons via Coulomb collisions is pointed out. If the bounce period of trapped electrons is less than their collisional relaxation time, the most part of the toroidal current is generated due to collisional dragging of non-resonant electrons.The author gratefully acknowledges valuable discussions with K.Jungwirth, V.Kopecký, V. L.Sizonenko and K. N.Stepanov.     

Quantum box resonant tunneling spectroscopy: Experiments and modelisation

We have calculated the potential profile and the electronic levels in resonant tunneling double barrier structures with nanometric lateral dimensions (≤ 500 nm) for various contact doping. At biases for which the box states (laterally confined quantum well) are resonant with the emitter Fermi level, fine structures are expected in the resonant tunneling current. Comparison with I(V) characteristics measured on nanometric GaAs/GaAlAs and GaAs/GaAlAs/InGaAs resonant tunneling diodes shows that our model accounts for the resonance bias voltage and explains the shape of the current peak. The fine structure observed in the current peak provides a spectroscopy of the confined states in the quantum box.     

离子迴旋共振加热对低杂波电流驱动的影响

离子迴旋共振频率(ICRF)波(ω=2Ω_D)和低杂(LH)波同时进入D-T聚变反应堆等离子体时,ICRF加热产生的高能D离子对LH波存在着较强的Landau阻尼吸收,影响了低杂波驱动电流(LHCD)的效率;提高LH波的频率,可降低加热离子对LH波的阻尼吸收。     

Structure and piezoelectric properties of 1-μm-thick polar-axis-oriented CaBi<Subscript>4</Subscript>Ti<Subscript>4</Subscript>O<Subscript>15</Subscript> films

1-μm-thick polar-axis-oriented CaBi₄Ti₄O₁₅ (CBTi144) films were fabricated by control of nucleation and growth in alkoxy-derived non-crystalline layers on Pt foils. The oxygen ambient during pre-baking impacted both the cross-sectional microstructure and the crystallographic orientation. The 1-μm-thick film showed relatively high intensities of (100)/(010) diffraction lines in the X-ray diffraction profile and simultaneously had a closely packed dense structure in the transmission electron microscopy cross-sectional profile. Resultantly, the leakage current density decreased to about 7×10^-8 A/cm² at 10 V. The piezoelectric constant d₃₃ was determined to be 260 pm/V at a maximum poling voltage of 60 V by measurements using piezoelectric force microscopy. PACS 77.55.+f; 77.84.-s; 77.65.-j; 68.55.Jk     

Scattering of electromagnetic waves by traveling-wave structures in the ionosphere

The diffraction of electromagnetic waves, incident obliquely on an ionospheric layer with density inhomogeneities of the traveling-wave type, is investigated by S. M. Rytov's method of smooth perturbations. The spatial dependencies of the properties of the ionosphere and of the wavelike inhomogeneities are taken into consideration. The diffraction patterns are analyzed for several variants of height profiles of the wave perturbations. The solutions obtained make it possible to estimate the effect of the form of ionospheric profile and the distribution of the level of disturbance of the wavelike inhomogeneities with respect to altitude on the diffraction effects.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 12, pp. 1717–1727, December, 1978.The author expresses his appreciation to V. N. Krasil'nikov for attention and advice.     

Field emission from single-walled carbon nanotubes aligned on a gold plate using a self-assembly monolayer

Field emission from single-walled carbon nanotubes (SWNTs) aligned on a patterned gold surface is reported. The SWNT emitters were prepared at room temperature by a self-assembly monolayer technique. SWNTs were cut into sub-micron lengths by sonication in an acidic solution. Cut SWNTs were attached to the gold surface by the reaction between the thiol groups and the gold surface. The field-emission measurements showed that the turn-on field was 4.8 V/μm at an emission current density of 10 μA/cm². The current density was 0.5 mA/cm² at 6.6 V/μm. This approach provides a novel route for fabricating CNT-based field-emission displays. Received: 3 May 2002 / Accepted: 6 May 2002 / Published online: 4 December 2002 RID="*" ID="*"Corresponding author. Fax: +82-54/279-8298, E-mail: ce20047@postech.ac.kr     

The electric polarization induced by temperature gradient and associated thermoelectric effects

It is shown that the possible existence of a direct effect, which consists in the production of electric polarization in a temperature gradient, is connected with the existence of effects that are analogous to the known thermoelectric effects. The thermoelectric effects under study play a role in a periodic regime of temperature and electric current.The author expresses his thanks to Dr. V. Janovec, Ph. D., Dr. V. Dvoák, Ph. D., and Assoc. Prof. Dr. J. Kvasnica, Ph. D. for their valuable comments on this paper.     

单相合金凝固过程时间相关的界面稳定性(I)理论分析

对定向凝固界面前沿非稳态溶质扩散场进行了系统的对比分析，发现无论在纯扩散还是存在对流的情况下，界面前沿的溶质扩散场通常满足指数分布的形式，可以采用一个统一的公式来描述界面前沿的瞬态溶质扩散场.进而在此基础上，对定向凝固界面形态稳定性进行了统一的时间相关的非稳态分析，发现界面临界稳定性条件的数学描述形式与Mullins和Seker ka理论给出的稳态解完全一致, 只是用时间相关的浓度梯度GtC、界面速度Vi、溶质扩散长度l代替了稳态生长中所得到的GC,V，DL/V.     

Plasma doping dosimetry

Plasma immersion ion implantation (PIII) is a large-area doping technique that can provide very high implant current at very low implant energy. Multiple ion species, plasma conditions, and implanter current-voltage waveforms in PIII lead to an exponential implant profile which is different from conventional implant profiles. A methodology is developed for using in situ measurements of the implanter current (I) and implant voltage (V) to derive an energy spectrum for a single implant pulse. The advantage of this technique is that a per-pulse profile may be determined experimentally, even in the presence of substrate etching, without any need for an implant model. If the ion species concentrations in the plasma are known, the energy spectrum found from the ion current and voltage waveforms can be used to construct a per-pulse implant profile. If the ion species distribution is not known a priori for a multispecies plasma, secondary ion mass spectroscopy (SIMS) data from an implanted sample can be used to estimate the ion species distribution and calibrate the IV-generated profile within a factor of two. Data from 1-5 kV, 2.5-5 kHz BF₃ PIII implants are used to demonstrate the concept. The implant profile for a single pulse can then be used to project the final implant profile and total implanted dose as a function of implant time, Pm pulse frequency, and substrate etching. In this work, an estimated secondary electron yield function is used to separate the total implant current into ion and secondary electron current components. The 25% dose variation error introduced by this effective secondary electron yield function could be avoided in a system which can measure ion current directly     

On the theory of instability in an ionospheric current jet

The generation of potential waves by a transverse current is considered in the region of an ionospheric electrojet. The numerical method is used to solve the dispersion equation for the case of weak currents and low growth rates. The region of low hybrid resonance is investigated analytically; the dispersion curves and the dependence of the growth rates on the wave number and the parameters of the ionospheric plasma are found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 15, No. 4, pp. 497–503, April, 1972.The author thanks V. Yu. Trakhtengerts for his constant attention to the work and his numerous discussions.     

On the influence of radiation wavelength on the efficiency of excitation of near-surface waveguides

We show the results of numerical study of the dependence of narrow radio-beam propagation on the wavelength in a near-surface waveguide formed above the calm sea. The waveguide excitation efficiency, which is understood as a trapped part of the current beam power, and the waveguide-power loss rate due to diffraction-de-excitation have been found for wavelengths in the range of 0.8–10 cm and vertical profile of refractive index close to those really observed in the atmosphere Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 7, pp. 882–890, July, 1996.The author thanks A. Yu. Derkach and N. P. Santalov for assistance in computations.     

Conduction mechanisms in pyrolytically grown dielectrics

Various conduction mechanisms in thin SiO₂, Al₂O₃, In₂O₃ layers were investigated experimentally by analyzing the behavior of the current as a function of field strength and temperature. The films were obtained by pyrolytic dissociation of organic compounds in the vapor phase.The author is indebted to P. S. Kireev for guidance, and to M. I. Elinson and V. B. Sandomirskii for interest in the investigation.     

Random fields in Ge-Si alloys produced by doping

A calculation is performed and estimates made of the binary correlation functions of the random field produced by the difference in the atomic pseudopotentials of solvent and dissolved materials. Also evaluated are elastic deformation fields in unordered Ge-Si solid replacement solutions with low Si content (up to 10 at. %).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 41–46, February, 1987.The author heartily thanks V. L. Bonch-Bruevich for his interest in the current study and many valuable discussions.     

Current electric quadrupole moments of atoms and nuclei

It is shown that current electric multipoles exist. Their field is electrostatic and it is unrelated to the existence of a net electric charge. At long range, it is the same as the field of the corresponding charge electric multipoles. Current electric multipoles arise during the motion of magnetic multipoles. An orbital motion of magnetic dipoles, a precession of a current-carrying loop, and the motion of magnetic quadrupoles all lead to current electric quadrupole moments. Expressions for the current electric quadrupole moments of atoms and nuclei are derived.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 53–58, July, 1991.The author wishes to thank S. A. Kuten' and V. I. Rapoport for useful comments offered during the writing of this paper and for a discussion of the results.     

Fabrication and characteristics of lateral Ti/4H-SiC Schottky barrier diodes

This paper describes the fabrication and characteristics of the lateral Ti/4H-SiC Schottky barrier diodes (SBDs). SBDs are fabricated by nitrogen ion implantation into p-type 4H-SiC epitaxial layer. The implant depth profile is simulated using the Monte Carlo simulator TRIM. Measurements of the reverse I－V characteristics demonstrate a low reverse current, that is good enough for many SiC-based devices such as SiC metal-semiconductor field-effect transistors, and SiC static induction transistors. The parameters of the diodes are extracted from the forward I－V characteristics. The barrier height φ_b of Ti/4H-SiC is 0.95 eV.     

A new method of calculating the spectrum and the self-consistent field of negative ions

A new method is suggested for negative ion calculations, based on perturbation theory with a model zeroth approximation and a polarization potential formalism. The binding energy of an electron in an Na^– ion is calculated as a test, and is found to agree with experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 41–46, September, 1990.In conclusion, the author is grateful to E. P. Ivanova for her interest, to V. V. Flambaum and V. K. Ivanov for supplying preprints of [8, 9], and to V. V. Filatov for help in the numerical calculations.