HL—1装置脉冲送气控制等离子体密度实验

本文描述HL-1装置用脉冲送气控制等离子体密度的实验。其结果表明等离子体建立后工作气体的快速注入(即边缘加料)能提高等离子体密度,改善等离子体性能。在较好地控制装置放电条件后(主要是等离子体电流,位移和杂质控制),多脉冲或长脉冲补充送气能在较宽范围内(0.8—7.0×10~(19)·m~(-3))有效地控制等离子体密度及波形,装置稳定运行区域大为扩展。最后讨论了器壁再循环对密度控制的影响和送气的加料效率。     

HL—1装置等离子体密度反馈实验

本文叙述HL-1装置用反馈脉冲补充送气方式控制等离子体密度的方法及实验结果。给出了在固有的物理实验条件下的最佳反馈方式,实现了对密度的有效控制及反馈。讨论了在不同密度条件下的几种反馈方式及反馈系统尚存在的不足之处。     

HL-1装置杂质控制与补充送气初步实验

将部分真空室内壁蒸钛,使Z_(eff)降低到2左右,电流坪区拉长到近400ms。用多个窄脉冲补充送气,获得了密度较高的等离子体,最大达到3. 7×10~(13)cm。实验结果表明,当前改善HL-1装置放电品质的关键在于控制杂质。     

HL-1装置碳氧杂质的质谱分析

本文描述了分析等离子体中C,O杂质的质谱法;用快速测量系统记录了杂质组分的时间行为;根据实验波形估算了HL-1等离子体中C+O的平均密度在脉冲送气下为4.5×10~11cm~(-3),连续送气下为6.1×10~11cm~(-3);由此等离子体中C+O的百分含量约为2％。     

HL-1装置脉冲送气的数值研究

本文采用一维等离子体输运模型,研究了脉冲送气对HL-1装置等离子体的影响。脉冲送气使等离子体密度提高1—2倍,能量约束时间增长50％,离子温度也有所提高;脉冲送气过程中,等离子体边缘迅速冷却,电流通道收缩,中心区域电子温度平直化。     

氰化氢激光干涉仪测量HL-1装置等离子体电子密度

本文叙述在HL-1装置上为测量平均电子密度n_e(i)而建立的,长探测臂迈克尔逊(Michelson)型转动光栅调相式氰化氢激光干涉仪(长臂HCN激光干涉仪)及其实验结果。并采用Apple-Ⅱ微机对密度数据进行实时处理,在脉冲送气实验中和破裂不稳定性发生时,观测了电子密度变化。本实验在电子密度(1—3)×10~(13)cm~(-3)范围内的测量误差约为(4—10)％。     

HL-1装置(?)_(eff)值的光谱法测量

利用光谱方法,在HL-1托卡马克装置上,测量了波长536nm附近等离子体轫致辐射连续谱的绝对强度。由此得到等离子体赤道平面中心弦的Z_(eff),并研究了蒸钛和脉冲送气对Z_(eff)的影响。在一系列放电中,未加蒸钛和脉冲送气时,接近中心区的Z_(eff)值为4—10,加蒸钛和多脉冲送气时,Z_(eff)值降到2.6—4。     

用钛吸气方法改善HL-1装置的等离子体性能

用钛吸气方法减少了HL-1托卡马克等离子体中的杂质和气体再循环率,使Z_(eff)降低到1.6;在程序控制送气技术的配合下,有效地控制了密度变化,获得线平均密度元_max=4.9×10~(19)m~(-3)的较高密度的稳定放电;成功地扩展了运行参数空间。     

中国环流器二号A(HL-2A)超声分子束注入最新结果

HL-2A装置电子回旋共振加热时,氘脉冲超声分子束穿越分界面,等离子体各项重要参数,包括等离子体储能、极向比压、中平面线平均密度、中心密度和温度上升,中子产额急剧增加. 超声分子束注入有可能较常规脉冲送气在台基顶部提供较强的粒子源,被认为是可供ITER替换脉冲送气的加料方法之一. HL-2A装置氢超声分子束注入的平均速度约为1.7km,与溢流(分子流)注入真空的速度测量作了比较. 关键词： 超声分子束注入 托卡马克 飞行时间法 加料     

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用密度调制的方法研究了等离子体中粒子输运问题。采用了注入脉冲式补充送气和超声分子束两种不同的密度调制方法。在HL-2A装置常规欧姆放电的情况下,运用有限差分法和Nagashima矩阵技术,求解了粒子平衡方程。计算出了粒子的输运系数(对流速度v和扩散系数D)。研究了粒子输运系数与等离子体线平均密度之间的关系。实验结果表明,在欧姆放电的情况下,等离子体芯部的粒子对流速度方向始终是向内的,并且密度低时,粒子输运系数(粒子扩散系数D和对流速度v)较大;密度高时,粒子输运系数较小。     

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.     

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.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.