“A=2托卡马克堆芯等离子体基本特性研究”2006年进展

主要涉及两方面的研究内容：第一是托卡马克等离子体的磁流体气球模稳定性研究；第二是HL-2A装置电子回旋加热有关的基础理论问题。包括三方面研究成果：（1）简要报道了关于负剪切区电阻气球模不稳定性及本征函数特性，给出了增长率与等离子体参数的定标关系；（2）利用Solov’ev位形中严格的气球模方程，讨论了应用广泛的s，α平衡模型的正确性；（3）计算分析了由弱磁场侧垂直入射的电子回旋波寻常模在HL-2A等离子体中的功率沉积剖面。     

静电堵漏串级镜MM—4U贩约束位形的理论研究

本文分析了双会切静电堵漏串级磁镜ＭＭ－４Ｕ中粒子损失的可能机制，考虑了 等离子体粒子能量的切断，从平衡的Ｖｌａｓｏｖ方程的解出发，数值求解了一组静态的达朗倍尔方程，即Ｐｏｉｓｓｏｎ方程和Ｍａｘｗｅｌｌ方程，得到了等离子体电位，密度及非中性度（净余电子数密度）分布。结果表明，堵漏电压及堵漏电极板的几何位形，磁场位形及磁场大小，电子温度电子－离子温度比在串级磁镜的束位形的形成中起着重要的作用。     

静电堵漏串级镜MM－4U的约束位形的理论研究

本文分析了双会切静电堵漏串级磁镜ＭＭ－４Ｕ中粒子损失的可能机制，考虑了等离子体粒子能量的切断，从平衡的Ｖｌａｓｏｖ方程的解出发，数值求解了一组静态的达朗倍尔方程，即Ｐｏｉｓｓｏｎ方程和Ｍａｘｗｅｌｌ方程，得到了等离子体电位、密度及非中性度（净余电子数密度）分布。结果表明，堵漏电压及堵漏电极极板的几何位形、磁场位形及磁场大小、电子温度及电子－离子温度比在串级磁镜的约束位形的形成中起着重要的作用。     

载流等离子体中的气球涡旋

本文研究载流等离子体中的非线性气球模。我们导出描述载流等离子体中的非线性气球模的方程组,求出该方程组的偶极涡旋解。它们属于Rossby型涡旋。结果表明,电子成份的定向运动将显著地影响涡旋的性质。     

磁镜中晃荡电子形成热垒的实验研究

本文在实验上研究了ＥＣＲＨ产生晃荡电子形成串级磁镜热垒的可行性，并对等离子体电位进行了测量。研究结果表明，ＥＣＲＨ产生晃荡电子形成热垒是成功的。     

托卡马克理想磁流体不稳定性的统一描述 (I)

在与平衡磁面相联系的坐标系下，用剪切阿尔芬波近似给出了统一描述托卡马克等离子体理想磁流体线性运动的本征模方程。利用此方程，可以进一步给出大尺度扰动（扭曲模、低模数气球模、阿尔芬模）和小尺度扰动（高模数气球模、Mercier模）的本征模方程。本文详细讨论了小尺度扰动的本征模方程。     

托卡马克等离子体中动力剪切阿尔芬波不稳定性的数值研究

用积分本征模方程研究了在托卡马克等离子体中包含全部动力学效应的动力剪切阿尔芬波模 (无论是否存在温度梯度). 引入了一个新的积分变量，将实平面的积分解析延拓到复平面. 这样可以同时研究增长模和阻尼模. 结果表明，在有离子温度梯度(ITG)的情况下，激发动 力剪切阿尔芬不稳定性所需的等离子体压强梯度比激发理想磁流体动力学气球模不稳定性的 阈值低得多，没有ITG时两者相同. 与动力无碰撞气球模结果不同，当有限ITG存在时，剪切 阿尔芬模存在第二稳定区. 关键词： 动力剪切阿尔芬模 磁流体气球模 阈值压强梯度     

热电子与热离子共存时的电荷裸露效应

本文采用简晰的平板模型，在局域近似下讨论了热电子，热离子共存时它们对低频交换模的影响，分析了两种热成分电荷裸露效应的相互作用。     

等离子体形变对边界局域模的作用研究

在磁流体模拟代码BOUT++剥离气球模三场模块框架下研究了等离子体形变参数(拉长比和三角形变)对边界局域模的影响。研究表明,在线性阶段,拉长比主要作用于剥离气球模中气球模成分,抑制了环向模数较高的气球模不稳定性;而三角形变则对剥离气球模中剥离模成分和气球模成分均有抑制作用。在非线性阶段,拉长比导致边界E×B剪切率增加,迫使压强扰动的正值部分向等离子体芯部发展,导致边界局域模的能量损失增加;三角形变则导致边界E×B剪切率降低,使得压强扰动可以向等离子体边缘发展,台基向等离子体芯部的崩塌减弱,从而对边界局域模起到缓解作用。     

电子回旋波使磁镜中捕获电子与逃逸电子相互转化

在Littlejohn的带电粒子引导中心拉格朗日体系下,讨论了电子回旋波对磁镜等离子体中捕获电子与逃逸电子的影响,给出了捕获电子变成逃逸电子以及逃逸电子被电子回旋波捕获的条件,并计算了它们的相互转化的概率。 关键词：     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.