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。     

HL—1装置电流上升段辐射与杂质特性

托卡马克等离子体中的杂质会影响托卡马克的放电品质及等离子体特性。许多理论和实验对杂质的产生和输运做了深入详细的研究。等离子体电流起始阶段,由于约束性能不好,会引起大量的杂质产生,辐射损失增大是杂质增加引起的直接后果。杂质辐射是等离子体辐射的主要组成部分之一,等离子体线辐射功率～Z_(eff)~6,复合辐射功率～Z_(eff)~4,轫致辐     

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。     

中性束注入加热下旋转和Z_(eff)对EAST中子出射影响的研究

为了判断中性束注入加热效果和研究等离子体宏观旋转和有效电荷数(Z_(eff))对中子出射的影响,结合实验数据,利用TRANSP模拟程序研究了EAST中性束注入加热时,等离子体旋转速度、有效电荷数Z_(eff)以及等离子体储能与中子出射率的关系。模拟结果表明,在能量为65keV、功率为2.89MW的中性束注入加热时,等离子体产生较大的旋转,旋转减少快离子热化时间,降低中子产额;有效电荷数Z_(eff)增加时,快离子投掷角散射增强,束靶反应减少,中子产额缩减。中子出射率随等离子体储能的增加而增加。     

PICPMCC 数值模拟四阳极直流辉光放电

利用OOPIC 代码并结合MCC 方法考察四阳极低气压直流辉光放电中粒子间的碰撞, 并对其进行了数值模拟。首先分析OOPIC 代码的计算流程, 给出模拟的边界条件和时间、空间步进; 然后对所得到的等离子体密度、温度的分布情况进行了分析。结果表明, 放电气压、电流以及环电极的有效宽度均影响等离子体密度和温度的径向分布。当气压为300Pa 时, 电子密度在径向较大范围内是均匀分布的, 而当气压升高到800Pa 时, 其径向不均匀增大, 且总的密度和电子的平均温度下降。放电电流的增大使得等离子体密度和温度均相应升高。但环电极有效宽度的减小使得等离子体密度的分布更不均匀, 并使总的密度和平均温度均下降。     

13.56 MHz/2 MHz柱状感性耦合等离子体参数的对比研究

通过Langmuir双探针和发射光谱诊断方法,对比研究了驱动频率为13.56 MHz和2 MHz柱状感性耦合等离子体中电子密度和电子温度的径向分布规律.结果表明:在高频和低频放电中,输入功率的增加对等离子体参数产生了不同的影响,高频放电中主要提升了电子密度,低频放电中则主要提升了电子温度.固定气压为10 Pa,分别由高频和低频驱动时,电子密度的径向分布均为"凸型".而电子温度的分布差异比较明显,高频驱动时,电子温度在腔室中心较为平坦,在边缘略有上升;低频驱动时,电子温度随径向距离的增加而逐渐下降.为了进一步分析造成这种差异的原因,在相同放电条件下采集了氩等离子体的发射光谱图,利用分支比法计算了亚稳态粒子的数密度,发现电子温度的径向分布始终与亚稳态粒子的径向分布相反.继续升高气压到100 Pa,发现不论高频还是低频放电,电子密度的径向分布均从"凸型"转变为"马鞍形",较低气压时电子密度的均匀性有了一定的提升,但低频的均匀性更好.     

低压氩气电感耦合等离子体特性分析及光谱诊断

电感耦合等离子体具有电子密度高、放电面积大、工作气压宽、结构简单等特点,在等离子体隐身领域具有突出的潜在优势。相对于开放式等离子体,闭式等离子体更适应于飞行器表面空气流速高、气压变化大的特殊环境。研究着眼于飞行器关键部件的局部隐身应用,设计了一种镶嵌于不锈钢壁中的圆柱形石英腔体结构,利用电感耦合放电的方式在腔体中产生均匀的平板状等离子体。由于增加了接地金属,降低了腔体内的钳制电位,同之前的纯石英腔体相比,该结构显著改善了等离子体的均匀性。研究了该闭式腔体内氩气电感耦合等离子体（ICP）的放电特性和发射光谱,实验中放电功率达到150 W时,可以明显观察到ICP的E-H模式转换,此时发射光谱和电子密度都呈现阶跃式增长。氩气发射光谱强度随放电功率升高显著增加,但是不同谱线强度增加幅度并不一致,分析认为是受不同的跃迁概率和激发能的影响。根据等离子体的发射光谱,利用玻尔兹曼斜率法对电子激发温度进行诊断,得到电子激发温度在2 000 K以上,并且随功率升高而降低,因为功率增大使电子热运动增强,粒子间的碰撞加剧,碰撞导致的能量消耗也更大。电子激发温度沿腔体径向呈近似均匀分布,分布趋势受功率影响不大。针对利用发射光谱诊断电子密度误差较大、计算繁琐的问题,引入Voigt卷积函数,经过拟合滤除多余展宽项的影响,得到准确的Stark展宽半高宽。最终利用发射光谱Stark展宽法计算了电子密度,腔体中心处的峰值密度可以达到7.5×1017 m-3。随着放电功率增大,线圈中容性分量降低,耦合效率增大,电子密度随之增大,但空间分布趋势基本不受功率影响。     

常压针-板放电等离子体密度演化

分别采用Stark展宽法、图像法诊断等离子体电子密度,研究常压针-板放电等离子体电子密度随放电参数的演化.实验结果表明,降低电源的脉冲频率,减小等离子体的电极间距和采用细径电极,都有助于提高等离子体密度.利用全局模型分析影响电子密度变化的因素可知,随着脉冲频率的下降,等离子体放电体积减小,导致电子密度上升.在电极间距减小的过程中,电子密度变化则是降低等离子体吸收功率与减小放电体积共同作用的结果,其中放电体积的减小起到了更为主导的作用,导致电子密度上升.此外,采用细径电极也可以使等离子体放电体积减小,从而有利于获得较高的电子密度.     

四阳极直流辉光放电正柱区数值分析

分析了具有中间开窗电极四阳极直流辉光放电装置的氦气放电中阴极与较近阳极间放电正柱区的电子密度、电子温度和等离子体碰撞频率, 及其空间分布随放电气压变化规律。结果表明电子密度在径向上呈类似于抛物线的分布, 而碰撞频率和电子温度在整个放电管内近似均匀分布。探讨了不锈钢阳极座和矩形窗口对这些参数的影响, 为进一步进行装置仿真和实验研究提供参考。     

外电极长度对同轴枪放电等离子体特性的影响

同轴枪放电装置能够产生高速度(～100 km/s)、高电子密度(～1016 cm–3)以及高能量密度(～1 MJ/m2)的稠密等离子体,因而在聚变能、天体物理及航空航天等领域得到了广泛关注.通过光电信号的测量以及对输运过程中等离子体时空演化过程的观察,本文主要对比分析了不同长度外电极下的同轴枪放电等离子体特性.外电极长度的增加,带来了喷射等离子体电子密度、发光强度的降低以及轴向速度、准直性与输运距离的显著提高,而由箍缩效应所形成的等离子体柱在放电过程中对中心电极的延长作用则是引起长短外电极同轴枪中等离子体参数差异的主要原因.延长的中心电极一方面与长外电极在轴向长度上得以匹配,使等离子体在枪内能够获得更长的加速时间,进而提高其喷射速度;另一方面则会造成带电粒子的大量损耗以及更高的碰撞复合损失,导致等离子体电子密度与发光强度的降低.等离子体的轴向动能直接影响着其喷出后的传播距离,而喷口处等离子体的扩散角则主要受电子密度与径向洛伦兹力的约束,二者共同决定了等离子体的准直性及输运衰减特性.     

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通过中平面活动10探针组、往复快速扫描4探针和低杂波天线口的固定4探针测量了主等离子体边缘的温度、密度、悬浮电位、径向和极向电场、雷诺协强、径向和极向等离子体流速及其径向分布。用偏滤器靶板上的14组嵌入式静电3探针阵列测量了同一环向截面的内外中性化板上的电子温度、密度、悬浮电位及其分布。比较了在孔栏位形和偏滤器位形下边缘等离子体特性的差异,特别是两种位形下边缘温度和密度衰减长度的变化。分析了在多脉冲超声分子束加料和低杂波注入条件下的边界等离子体特性,以及雷诺协强的径向梯度与极向流和径向电场梯度与湍流损失的相互关系。     

HT-7超导托卡马克边界等离子体参量及其涨落的实验研究

利用径向可移动朗缪尔三探针和马赫探针对HT-7超导托卡马克边界等离子体参量及其涨落进行了空时空分辨测量.给出了欧姆放电及其与低杂波电流驱动共同作用下边界等离子体电位φ_p、电子温度T_e和电子密度n_e及其涨落的径向分布.实验表明,在限制器附近,存在一由E_r×B确定的极向旋转速度剪切层.在剪切层内,T_e和n_e分布较陡,且φ_p,T_e和n_e的相对涨落水平下降明显.这说明剪切层对边界区的等离子体涨落具有抑制作用.低杂波驱动使径向电场梯度变陡,从而使剪切程度加深但对剪切层宽度无影响.此外,测量表明等离子体环向速度马赫数M_φ存在径向梯度.环向流的这种径向梯度可能是形成径向电场所需的平均极向流的一种重要驱动源 关键词： 托卡马克 边界涨落 低杂波驱动     

Observations of Edge Plasma on HL-2A Tokamak

The edge plasma characteristics are studied by a movable array of Mach/Reynolds stress/Langmuir 10-probes and fast reciprocating 4-probes in the boundary region. These probes can measure edge plasma temperature, density, poloidal electric field, radial electric field, Reynolds stress, poloidal rotation velocities and their profiles obtained by changing the radial positions of the probe array in different discharges. Measurement resuits are used to analyze plasma confinement, turbulent fluctuations and their correlation. The fixed flush 3-probe arrays are mounted on the 4-divertor neutralization plates at the same toroidal cross-section in divertor chamber. These probes are used to measure the profiles of the electron temperature, density and float potential in divertor chamber.     

HL-2A等离子体边缘的快速单探针测量

介绍了对HL-2A装置中平面边缘等离子体的单探针测量。单探针是安装在可径向移动、并可绕轴旋 转360o的传动杆上的。在1MHz的快速采样频率下,测量了主等离子体边缘的温度、密度、悬浮电位、空间电位、极 向等离子体流速的径向分布。测量的结果表明,利用单探针测量的主等离子体边缘参数与朗缪尔四探针测量结果 基本一致。     

Effects of Applied DC Radial Electric Fields on Particle Transport in a Bumpy Torus Plasma

The toroidal ring of plasma contained in the NASA Lewis Bumpy Torus may be biased to positive or negative potentials approaching 50 kilovolts by applying DC voltage to twelve or fewer midplane electrode rings. The electric fields, which are responsible for raising the ions to high energies by ExB/B2 drift, then point radially outward or inward. The profiles of plasma number density are observed to be flat or triangular across the plasma diameter. The absence of a second derivative in the density profile, combined with the flat electron temperature profiles which are observed, implies that the radial transport processes are not diffusional in nature and are dominated by the strong radial electric fields which are applied to the plasma. Evidence from a paired comparison test shows that the plasma number density and confinement time can increase more than an order of magnitude if the electric field acting along the minor radius of the toroidal plasma points inward, relative to the values observed when the electric field points radially outward. Some characteristic data taken under nonoptimized conditions yielded the highest plasma number density (2.7 × 1011/cc on axis) and the longest particle containment times (1.9 milliseconds) observed so far in this experiment.     

Density Fluctuation Measurements Using FIR Interferometer on HL-2A Tokamak

Density fluctuations were first measured in the core region of HL-2A tokamak plasma using a newly developed multi-channel FIR interferometer system. In divertor ohmic discharges, we measured the radial density fluctuation levels of 5%, which increase to 10-20% during the appearance of MHD activity. Most of the power density in the density fluctuation spectrum is directly associated with m = 2 tearing modes. The fluctuation levels reduce to 1/3 and plasma confinement is improved during off-axis electron-cyclotron-resonance heating （ECRH）.     

Inreased Power Concentration and its Effect on the Discharge Parameters on the Low Pressure Hg-Rare Gas Positive Column III. Effects of an Axial Rod

After the investigation of the influence of current and tube radius on the power concentration of the Hg-rare gas discharge in the two previous parts, part III deals with the corresponding effects of additional recombination surfaces. The plasma parameters (radiant flux of the resonance lines, field strength, electron density, electron energy distribution function) are measured in a discharge tube with an axial glass rod. With increasing rod diameter and increasing distance from the tube axis radial radiation intensity distribution becomes asymmetric. The field strength increases with the radius of the rod. The dependence of the field strength and that of the radiant flux on the parameters of the discharge do not basically change. The measured UV-radiation efficiency of the positive column is higher than that of discharges without axial rod for equal tube radius. This is attributed primarily to the changed radial electron density distribution and its effect on the collision processes.     

Two-dimensional, self-consistent, three-moment simulation of RFglow discharge

A two-dimensional self-consistent nonequilibrium fluid model is used to simulate radio frequency (RF) glow discharges to evaluate the quantitative effects of the radial and axial flow dynamics inside a cylindrically symmetric parallel-plate geometry. This model is based on the three moments of the Boltzmann equation and on Poisson's equation. Radial/axial flow dynamics of plasma in low-pressure parallel plate RF glow discharges are investigated. Instead of uniform profiles along the radial direction, which are assumed in one-dimensional models, nonplate profiles are obtained from the two-dimensional simulations. Ionization rate and three moment distributions of plasma density, average velocity, and mean energy are presented in a two-dimensional configuration. The maximum ionization rate occurs in the radial sheath region and agrees with experimental results. Variations in ion density distributions at different positions, various gas pressures frequencies, and applied fields are discussed     

Profile structures of TJ-II stellarator plasmas

Fine structures are found in the TJ-II stellarator electron temperature and density profiles, when they are measured using a high spatial resolution Thomson scattering system. These structures consist of peaks and valleys superimposed to a smooth average. Some irregularities remain in an ensemble average of discharges with similar macroscopic parameters such as line density, central temperature, and plasma current. They are found in all the magnetic configurations explored in plasmas heated by electron cyclotron waves. Their characteristics are shown and their possible origin is discussed.