拉瓦尔喷嘴的气流线质量及密度分析

喷气负载是高功率Z箍缩的主要负载之一。应用一维等熵压缩气体动力学，分析了“强光一号”加速器拉瓦尔喷嘴的基本物理过程，获得了拉瓦尔喷嘴出口处气流的马赫数，Ma=4.6，并对其进行了修正，修正值为3.5。利用由雪耙模型导出的Z箍缩聚爆时间表达式，并结合“强光一号”Z箍缩实验结果，修正了由一维等熵气体动力学得到的喷嘴气流线质量表达式。最后根据已知气流的线质量40 μg/cm ，利用B-T模型初步估算了喷嘴的气流密度分布。估算结果为:在轴向2.5~40 mm，径向0~15 mm的区域内，气体分子密度基本在1016～1017/cm3，且在轴向2 cm内基本形成空心的气体壳层结构。     

单壳层喷气Z箍缩内爆特性分析

在“阳”加速器（电流峰值为500—850 kA,上升时间约为85 ns）上利用单壳层喷气负载开展了Z箍缩等离子体内爆实验,获得了等离子体的辐射产额、X光辐射图像等诊断结果.利用相应的诊断结果,定义了内爆时间,对内爆过程的主要阶段进行了划分,研究了等离子体位形、辐射强度分布等实验现象,同时对等离子体的内爆轨迹、内爆质量、径向收缩比、磁流体不稳定性等进行了初步分析. 关键词： Z箍缩')" href="#">喷气负载Z箍缩 等离子体内爆 X光辐射功率 “阳”加速器     

双层喷气Z箍缩氖等离子体K层辐射研究

报道了"强光一号"(1.6 MA,70 ns)加速器驱动双层喷Ne气Z箍缩负载产生K层辐射(光子能量约1 keV)的实验研究.喷气负载出口半径为1.5—1.4 cm和0.75—0.6 cm(半径比2 ∶1).充气压力相同情况下外层和内层质量比约2.8 ∶1.在内爆时间约120 ns、负载线质量估计值60—70 μg/cm时,获得K层辐射产额约7 kJ、峰值功率0.28 TW,脉冲宽度20 ns.X射线分幅图像表明内爆阶段的不稳定性影响较小,最终内爆速度超过25 cm/μs,等离 关键词： 双层喷气 Z箍缩等离子体 K层辐射')" href="#">K层辐射 雪耙内爆     

喷气Z箍缩负载的质量线密度确定

 喷气Z箍缩的负载参数（如质量线密度及半径）必须和脉冲驱动源的电流（幅值和上升时间）相匹配。作者利用微型快速电离规测量了喷气Z箍缩中超音速喷嘴产生的气体负载的密度分布，并由此得到了负载质量线密度为43μg/cm，这符合原定的喷嘴设计指标。     

测量喷气Z箍缩负载的气流马赫数

 利用双压力传感器的方法测量了喷气Z箍缩负载的气流马赫数。测量得到的气流马赫数最高可达到4.25，它和定常计算的结果4.8很接近，这表明可以用定常计算来估算喷气Z箍缩中超声速喷嘴产生的气流马赫数。     

Z箍缩等离子体K壳层X射线自辐射单色成像

采用针孔配接对数螺线柱面晶体方案,研制了一种小型、靶室内置X射线单色成像器,用于获取Z箍缩等离子体K壳层自辐射单色图像。在阳加速器上对该成像器进行了测试,成功地获取了铝丝阵负载Z箍缩等离子体K壳层自辐射的类氢线与类氦线单色图像。实验结果表明:该成像器具有优异的单色性（能谱带宽小于1 eV）,适合于中低原子序数Z箍缩内爆负载的特征谱线单色图像诊断。     

喷气Z箍缩高速扫描摄影

内爆Z箍缩是一种强的软X射线源，它在核武器物理、核武器效应模拟和惯性聚变等方面有重要的应用前景。喷气Z箍缩是以气体作为负载来产生等离子体，其内爆技术的研究主要集中在20世纪80年代及90年代早期，等离子体半径、压缩速度与时间关系是压缩过程中最为基本的参数。在本次实验研究中，用高速变像管扫描相机首次拍摄了阳加速器在负载为氖气状态下等离子内爆箍缩过程具有时间分辨的扫描像。     

快Z箍缩钨丝阵内爆物理研究

 通过理论和实验研究了快Z箍缩电磁内爆动力学物理过程及其辐射特性，完成了1维和2维辐射磁流体动力学数值模拟程序。利用阳加速器、强光一号脉冲功率装置、S-300装置和Angara-5-1装置，开展了实验研究，发展了一系列观察Z箍缩等离子体辐射的诊断系统。研制了单层、双层钨丝阵及单层丝阵加聚氘乙烯芯等负载。重点研究了能量耦合和内爆动力学规律。     

“强光一号”装置上部分Z箍缩实验结果的物理分析

从原子的电离能和维持等离子体所需能量出发，给出了估算任一元素材料，要产生任一壳层的X射线辐射，每个离子(原子)所需要的基本能量和要达到的内爆箍缩速度的方法.对“强光一号”加速器上典型的氪喷气和部分钨丝阵Z箍缩实验的电流和电压波形所蕴涵的丰富物理信息进行了分析，得到了电感和洛伦兹(Lorentz)力做功等物理量的变化规律以及负载参数变化对它们的影响.该电感与基于壳层模型计算出的电感有较大的差异.前者随箍缩开始而缓慢增大，甚至在箍缩到心和飞散后还在增大，最后大致稳定在100 nH附近.差异可能是由于壳层模型过于简化和电流电压的测点同负载有一定的距离而造成的.当丝阵直径为8 mm时，洛伦兹力做功最大；当丝阵直径相同时，丝数较大时，洛伦兹力做功也较大.同时还对该加速器的喷气和丝阵负载的线质量进行了优化，表明也是直径为8 mm的钨丝阵为最佳负载，这同实验的优化结果也一致.     

“碰撞-辐射”模型在Z箍缩等离子体K壳层线辐射谱分析中的应用

介绍了由K壳层谱线强度比估算等离子体状态参数的"碰撞-辐射"模型的基本原理.详细描述了自行研制的基于该模型的Z箍缩等离子体K壳层线辐射谱分析程序——ZSPEC的基本情况.给出了氖等离子体的计算结果,包括不同电离态离子的相对含量随电子温度的变化曲线和K壳层谱线强度比在"电子密度-电子温度"平面内的等高线分布图.该程序已在"阳"加速器Z箍缩实验结果分析中得到应用,将椭圆晶体谱仪测得的氖等离子体K壳层谱线强度比与ZSPEC程序计算结果相比较,得出在该发实验 关键词： 碰撞-辐射模型 K壳层线辐射谱')" href="#">K壳层线辐射谱 氖气喷气Z箍缩 阳加速器     

Supersonic flow about a body exposed to electric and magnetic fields

The feasibility of using nonmechanical (electrogasdynamic, EGD, and magnetohydrodynamic, MHD) methods to control shock-wave configurations emerging in supersonic flows is investigated. In the EGD method, the flow is heated by a gas discharge; in the MHD one, the flow is influenced by a Lorentz force arising in a gas discharge upon applying a magnetic field. The influence of the gas discharge and MHD interaction on the position of a detached shock wave appearing in a supersonic xenon flow about a semicylindrical body is studied. A discharge is initiated in the immediate vicinity of the leading edge of the body, and the variation of the shock wave position with the intensity of the discharge (discharge current density) is traced when the influence of the EGD action increases and/or an external magnetic field is applied (the influence of the MHD action increases). Preliminary data for a supersonic air flow about a body are presented.     

Properties and applications of cold supersonic gas jet

By analyzing the formation mechanism of a supersonic gas jet, a set of equations which describe the atomic beam properties were established. The influence of initial temperature, initial pressure, background gas pressure and pumping speed was discussed in detail. A simulation program was developed based on the equations, and the results under different initial conditions were obtained. The results are in good agreement with the experimental data, and suggest that, in order to get much smaller transverse momentum in collision experiments, it is necessary to lower the initial temperature and the initial pressure of the supersonic gas jet, together with increasing the pumping speed. These results are very instructive for construction of a new generation of cold supersonic gas jets.     

Effects of gas pressure on plasma characteristics in dual frequency argon capacitive glow discharges at low pressure by a self-consistent fluid model

A self-consistent fluid model for dual radio frequency argon capacitive glow discharges at low pressure is established.Numerical results are obtained by using a finite difference method to solve the model numerically, and the results are analyzed to study the effect of gas pressure on the plasma characteristics. It shows that when the gas pressure increases from 0.3 Torr(1 Torr = 1.33322×10~2 Pa) to 1.5 Torr, the cycle-averaged plasma density and the ionization rate increase;the cycle-averaged ion current densities and ion energy densities on the electrodes electrode increase; the cycle-averaged electron temperature decreases. Also, the instantaneous electron density in the powered sheath region is presented and discussed. The cycle-averaged electric field has a complex behavior with the increasing of gas pressure, and its changes take place mainly in the two sheath regions. The cycle-averaged electron pressure heating, electron ohmic heating, electron heating, and electron energy loss are all influenced by the gas pressure. Two peaks of the electron heating appear in the sheath regions and the two peaks become larger and move to electrodes as the gas pressure increases.     

电子回旋共振等离子体密度均匀性的数值研究

基于漂移扩散近似,在轴对称假设下,对电子回旋共振等离子体源腔室内的等离子体建立了二维流体模型.采用有限差分法对所建立的模型进行了自洽数值模拟,得到了等离子体密度均匀性随时间演化的数值结果.通过对数值结果的分析,研究了背景气体压强、微波功率和磁场线圈电流对等离子体密度均匀性的影响.研究表明,在电离初期,电子密度的均匀性好于离子密度的均匀性.在电离后期,离子密度的均匀性好于电子密度的均匀性.随着背景气体压强的增大,电子密度和离子密度的均匀性都在增加,且离子密度的均匀性增加的更快.随着微波功率的增大,电子密度和 关键词： 等离子体密度均匀性 背景气体压强 微波功率 磁场线圈电流     

Acoustic disturbance from gas non-uniformities convected through a nozzle

The non-steady flow generated by convection of gas containing non-uniform temperature regions or “entropy spots” through a nozzle is examined analytically as a source of acoustic disturbance. The first portion of the investigation treats the “compact nozzle”, the case where all wave lengths are much longer than the nozzle. Strengths of transmitted and reflected one-dimensional waves are given for supersonic and subsonic nozzles and for one configuration of supersonic nozzle with normal shock at the outlet. In addition to a wave reflected from the nozzle inlet, the supersonic nozzle discharges two waves, one facing upstream and the other facing downstream. For reasonable values of the nozzle inlet Mach number, the pressure amplitude of each wave increases directly as the discharge Mach number.The acoustic perturbations from a supercritical nozzle of finite length, in which the undisturbed gas velocity increases linearly through the nozzle, are analyzed for several inlet and discharge Mach number values and over a wide frequency range. The results which agree with the compact analysis for low frequency, deviate considerably as the frequency rises, achieving pressure fluctuation levels of several times the compact values. It is shown that this result originates in a phase shift between the two waves emitted downstream and that the pressure fluctuations for moderate frequencies may be approximated from the compact analysis with an appropriate phase shift.In all cases, the pressure fluctuations caused by a 2% fluctuation in absolute inlet temperature are large enough to require consideration in acoustic analysis of nozzles or turbine blade channels.     

Supersonic CO2 laser excited by RF discharge in closed cycle

A supersonic gas flow having a Mach number of 2 has been realized in a closed-cycle radio-frequency (RF)-discharge-excited supersonic CO₂ laser system. Stable RF discharge at a high CO₂ gas concentration has become possible using supersonic gas flow and RF discharge generated between dielectric electrodes. As a result, high RF input power density has been obtained. In addition, a high small-signal gain has been obtained in the supersonic section through decreases in gas pressure and gas temperature due to supersonic gas flow.This revised version was published online in August 2005 with a corrected cover date.     

Plasma acceleration by area expansion

As the area of a plasma increases, the plasma can accelerate smoothly from subsonic to supersonic velocity. The singularity which ordinarily occurs at the sonic velocity is resolved not by charge separation, as is the case for a sheath, but rather by a zero in the numerator at the same spatial position as the zero in the denominator, the sonic point. That is, at the sonic point, the acceleration due to expansion just cancels out the deceleration due to ion and electron neutral collisions. It turns out that, in this configuration, the plasma can accelerate to about three times the ion sound speed. The electron temperature is determined by the geometry, gas species, and, mostly, by the gas pressure. Applications to the production of a stream of neutrals for etching, and to space plasma propulsion are discussed     

Enhanced Raman-scattering measurements in low-density supersonic flows

Raman scattering, enhanced by a light trapping cell, has been used to measure temperature and density in the inviscid and viscous regions of the flow from an open-jet supersonic nozzle. Raman temperatures and densities in the inviscid regions are in excellent agreement with static temperatures and densities calculated from measurements of stagnation temperature, stagnation pressure and Pitot pressure.     

多普勒漂移对超音速燃气流光辐射特性计算的影响

分析了超音速射流由于高速相对运动产生多普勒谱线漂移效应对光辐射特性计算的影响。通过采用逐线计算法对不同环境压力、气流温度、气流速度条件下超音速燃气射流在不同的红外光谱区(2.7微米谱带和4.3微米谱带)光辐射谱带积分强度的计算结果比较表明:多普勒漂移效应受环境总压影响最大,压力越大多普勒漂移的影响越小;随着温度升高多普勒漂移效应的影响降低;随着相对速度的增加,多普勒漂移效应的影响多数情况下是增加的。     

GAS DYNAMIC PROBLEMS CAUSED BY THE GENERATION OF THE RADICALS IN A SUPERSONIC JET

A simplified one-dimensional model was proposed to treat the gas dynamic problems in a supersonic jet, which was used to produce radicals cooled by supersonic expansion, Based on this model, the gas dynamic equations can be integrated directly to obtain the evolution or the translational temperature and the rotational temperature of free radicals as well as the molecule density. The results show that the heating position where the radicals are generated and the initial rotational temperature of radicals have little effect on the rotational temperature at the down stream detection point, if the heating position is close to the nozzle orifice.