Scaling of rise time of drive current on development of magneto-Rayleigh–Taylor instabilities for single-shell Z-pinches

In fast Z-pinches,rise time of drive current plays an important role in development of magneto-Rayleigh–Taylor(MRT)instabilities.It is essential for applications of Z-pinch dynamic hohlraum(ZPDH),which could be used for driving inertial confinement fusion(ICF),to understand the scaling of rise time on MRTs.Therefore,a theoretical model for nonlinear development of MRTs is developed according to the numerical analysis.It is found from the model that the implosion distance L=r_(0)-r_(mc)determines the development of MRTs,where r_(0)is the initial radius and rmc is the position of the accelerating shell.The current rise timeτwould affect the MRT development because of its strong coupling with the r;.The amplitude of MRTs would increase with the rise time linearly if an implosion velocity is specified.The effects of the rise time on MRT,in addition,are studied by numerical simulation.The results are consistent with those of the theoretical model very well.Finally,the scaling of the rise time on amplitude of MRTs is obtained for a specified implosion velocity by the theoretical model and numerical simulations.

Radiation characteristics and implosion dynamics of tungsten wire array Z-pinches on the YANG accelerator

We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ～ 90 ns.The arrays are made up of（8-32）×5 μm wires 6/10 mm in diameter and 15 mm in height.The highest X-ray power obtained in the experiments was about 0.37 TW with the total radiation energy ～ 13 kJ and the energy conversion efficiency ～ 9%（24×5 μm wires,6 mm in diameter）.Most of the X-ray emissions from tungsten Z-pinch plasmas were distributed in the spectral band of 100-600 eV,peaked at 250 and 375 eV.The dominant wavelengths of the wire ablation and the magneto-Rayleigh-Taylor instability were found and analyzed through measuring the time-gated self-emission and laser interferometric images.Through analyzing the implosion trajectories obtained by an optical streak camera,the run-in velocities of the Z-pinch plasmas at the end of the implosion phase were determined to be about（1.3-2.1）×10 7 cm/s.

Z-pinch内爆等离子体时空分辨诊断技术

为了深入认识和理解Z-pinch物理机制并对物理实验进行优化设计，需要研究内爆等离子体及其辐射的时空分布特性诊断技术，建立诊断装置与设备，通过实验研究等离子体内爆时间过程及其空间分布特性，利用所获得的实验诊断数据校核数值模拟程序。简要介绍近几年开展的X光空间积分功率谱测量、X光时间积分针孔照相、X光时分幅针孔照相、X光时间分辨1维空同分布、紫外探针阴影照相等时空分辨诊断技术研究工作，并给出在1～3MA电流驱动装置上进行的喷气和丝阵内爆实验中获得的部分时空分辨诊断结果，包括辐射功率、拉链速度、内爆速度、收缩比等。

弹簧支撑自适应Z-pinch单层柱面丝阵负载研制

在靶室阴、阳电极呈水平放置的电磁内爆加速器中,抽真空时电极间距会收缩变短,电极间的丝阵负载无法维持预定的分布状态,为此,设计出了一套单层柱面状丝阵负载制备技术,通过弹簧预先压缩足够长度使负载能自动适应电极间距变化,并利用一套可以拆卸的辅助装置固定负载各部件。对制备出的多种单层柱面丝阵负载的测试及靶场实验结果表明,负载能自动适应电极间距变化,最大收缩量达3mm,负载丝仍保持预定的分布并且绷紧,制备技术也便于负载的装配、运输和安装。

Z-pinch X射线时间分辨多幅图像诊断系统

介绍了为"强光一号"设计的ns级时间分辨软X射线多幅图像诊断系统,分析了系统的主要性能指标,给出并分析了利用该系统诊断"强光一号"高功率脉冲Z pinch等离子体辐射源的最新的实验结果。

Z-pinch靶用氘代聚苯乙烯丝的研制及表征

为满足Z-pinch D-D出中子实验对固体燃料容器的要求,设计了1套简易的拉丝装置,并用聚苯乙烯(PS)为原料进行了工艺条件实验,确定出较佳的实验条件.以1 g氘代聚苯乙烯(DPS)为原料,在确定出的实验条件下,控制合适的拉丝速度,可拉出直径为30～100 μm、均匀、具有一定强度的DPS丝.所制备的DPS丝在Z-pinch D-D出中子实验中得到了应用,取得了最大中子产额为2×109 cm-1的实验结果.

喷气Z-pinch高速扫描摄影技术研究

叙述了高速摄影在阳加速器喷气Z pinch实验中测量等离子体向心运动时的应用,用高速变像管扫描相机首次拍摄到阳加速器喷气负载为氖气状态下产生等离子体压缩过程的扫描像,该扫描像的时间分辨本领很高,可以观察到等离子体内爆压缩阶段整个过程,测得了该过程的直径随时间连续变化曲线。

Z-pinch装置轴向绝缘堆的设计和分析方法

通过分析比较国外Z pinch装置轴向绝缘堆的设计,对轴向绝缘堆设计中的关键问题进行了归纳与总结。在总体描述绝缘堆研制方法和思路的基础上,详细论述了静电场数值模拟、电感参数计算和电路模拟、闪络概率计算、结构稳定性力学分析以及材料选择等绝缘堆研制中的几个关键问题,并对闪络概率分析方法的完善和拓展应用进行了讨论。

分幅相机系统在丝阵Z-pinch实验中的应用

将皮秒分幅相机系统用于丝阵Z-pinch实验诊断中,获得了较好的实验结果,并对实验数据进行了初步的分析,利用皮秒分幅相机测得等离子体内爆速度达2×107cm/s,还测得了丝阵内爆的轴向不同时性及双区辐射现象。

预脉冲的抑制及Z-pinch实验可允许的预脉冲电压分析

分析了脉冲功率装置特别是使用Blumlein线装置的预脉冲电压的产生机理,提出了通过一个连接于Marx和地之间的附加电感来平衡充电电路以抑制预脉冲的方法。用Pspice计算的实例表明:使用该方法可以有效地减小预脉冲电压。使用金属丝的比作用量和汽化热两种计算方法分析了Z Pinch实验中丝阵负载可承受的预脉冲电压,计算结果与实验结果对比表明,实验中铝丝的预脉冲电流远大于计算结果的最大值,铝丝发生汽化,验证了计算方法的正确性。

一维时空分辨诊断技术在Z-pinch实验中的应用

在Angara-5-1装置上进行的丝阵Z-pinch实验中,红光塑料闪烁体薄膜将X光转换为可见光,通过光纤阵列、光纤传像束传输至可见光条纹像机(OSC),紧贴于像机屏幕的光纤锥将信号耦合至CCD进行记录,提供丝阵一维条纹像,观察丝阵负载Pinch区X射线辐射空间分布信息随时间的演化过程。实验中系统时间分辨4.3ns,空间分辨0.3mm。负载采用单层丝阵与双层丝阵。研究结果表明,X光辐射波形前沿上升时间越快,功率峰值越高;双层丝阵构形改善了内爆同步性;等离子体的内爆动能与电流成正比,电流愈大,等离子体的动能也愈大,X光辐射能量与电流成正比。

Z-Pinch驱动的次临界包层的初步热工分析

Z-Pinch产生高能脉冲中子驱动以压水堆乏燃料或天然铀为燃料的次临界包层,以能源输出为主要目标,是实现能源可持续发展的可行途径。本文通过理论计算,分析了次临界包层在连续中子脉冲作用下的材料温度和输出功率随时间的变化规律。结果表明,通过合理的设计可以使材料温度在可接受的范围内波动,系统输出功率在时间轴上可以得到稳定。

丝阵Z-pinch等离子体内爆过程单丝特性研究

研究了丝阵 Z-pinch 等离子体内爆过程中,单丝行为及其物理参数的匹配,X 射线的发射情况,并对单丝的内爆过程进行了数值模拟。利用丝阵 Z-pinch等离子体动力学—维模型,研制了相关的计算程序,对丝阵箍缩匹配关系进行了计算。给出了丝阵初始半径、电流脉冲宽度和峰值电流的匹配关系。还对丝阵内的最小丝间距,材料的选择等的等问题进行了优化研究。

用高灵敏度激光干涉仪测量Z-pinch喷气负载质量线密度

介绍了采用外差式记录系统和相位跟踪方法建立的高灵敏度(0.2°)迈克尔逊激光干涉系统对Z-pinch喷气负载质量线密度的测量。通过采用充气隔振光学平台和将干涉仪放置到喷气真空室内等隔振方法,有效地消除了机械振动对测量结果的影响,获得了拉瓦尔喷嘴产生的超音速Ar气喷气负载平均质量线密度随时间的变化曲线,为优化喷嘴理论设计程序提供了实验依据。气流稳态的建立时间可以用于精确控制喷气装置电磁阀门的打开时刻,保证喷气Z-pinch实验中脉冲功率装置提供的脉冲电流与喷气负载平顶之间的时间同步。

End-on x-ray backlighting experiments for axial diagnostics of wire-array Z-pinch plasma on PPG-1

An X-pinch axial backlighting system has been designed to quantitatively measure the density distribution of wirearray Z-pinch plasmas. End-on backlighting experiments were carried out on a 200 kA, 100 ns pulsed-power generator（PPG-1） at the Tsinghua University. Compared with side-on backlighting, end-on measurements provide an axial view of the evolution of Z-pinch plasmas. Early stages of 2-, 4-, and 8-wire Z-pinch plasmas were observed via point-projection backlighting radiography with a relatively high success rate. The density distribution of Z-pinch plasma on the r–θ plane was obtained directly from the images with the help of step wedges, and the inward radial velocity was calculated. The ablation rates obtained by X-pinch backlighting experiments are compared in detail with those calculated by the rocket model and the results show consistency.

单丝Z-Pinch等离子体Thomson散射诊断系统设计

介绍了根据"阳"加速器现场环境设计Thomson散射诊断系统的方法和思路。由本底辐射出发,研究了诊断系统的重要参数,如探针光的能量、脉宽以及各光学元件的参数;同时,给出探针光和收光系统光路的设计安排;最后,讨论了杂散光及噪声的来源,并给出抑制或降低其影响的方法。

X-ray observations of tungsten wire array Z-pinch implosions on QiangGuang-1 facility

Z-pinch experiments with two arrays consisting, respectively, of 32 4-μm- and 6-μm-diameter tungsten wires have been carried out on QiangGuang-1 facility with a current rising up to 1.5 MA in 80 ns. At early time of implosion, x-ray framing images show that the initial emission comes from the central part of arrays, and double clear emission rings, drifting to the anode and the cathode at 5×10^6 cm/s and 2.4×10^7 cm/s respectively, are often produced near the electrodes. Later, in a 4-μm-diameter tungsten wire array, filamentation caused by ohmic heating is prominent, and more than ten filaments have been observed. A radial inward shift of arrays starts at about 30 ns earlier than the occurrence of the x-ray peak power for both kinds of arrays, and the shrinkage rate of emission region is as high as 1.7×107 cm/s in a 4-μm-diameter tungsten wire array, which is two times higher than that in a 6-μm one. Emission from precursor plasmas is observed in implosion of 6-μm-diameter tungsten wire arrays, but not in implosion of a 4- μm-diameter tungsten wire array. Whereas, in a 4-μm-diameter tungsten wire array, the soft x-ray emission shows the growth of m=l instability in the plasma column, which is caused by current. The reasons for the discrepancy between implosions of 4-μm- and 6-μm-diameter tungsten wire arrays are explained.

Theoretical and numerical research of wire array Z-pinch and dynamic hohlraum at IAPCM

Dense Z-pinch plasmas are powerful and energy-efficient laboratory sources of X-rays,and show the possibility to drive inertial confinement fusion(ICF).Recent advances in wire-array Z-pinch and Z-pinch dynamic hohlraum(ZPDH)researches at the Institute of Applied Physics and Computational Mathematics are presented in this paper.Models are setup to study different physical processes.A full circuit model(FCM)was used to study the coupling between Z-pinch implosion and generator discharge.A mass injection model with azimuthal modulation was setup to simulate the wire-array plasma initiation,and the two-dimensional MHD code MARED was developed to investigate the Z-pinch implosion,MRT instability,stagnation and radiation.Implosions of nested and quasi-spherical wire arrays were also investigated theoretically and numerically.Key processes of ZPDH,such as the arrayefoam interaction,formation of the hohlraum radiation,as well as the following capsule ablation and implosion,were analyzed with different radiation magneto-hydrodynamics(RMHD)codes.An integrated 2D RMHD simulation of dynamic hohlraum driven capsule implosion provides us the physical insights of wire-array plasma acceleration,shock generation and propagation,hohlraum formation,radiation ablation,and fuel compression.

Electron temperature diagnostics of aluminium plasma in a z-pinch experiment at the "QiangGuang-1" facility

Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several ＂bright spots＂ indicate electron temperatures between （450 eV- 520 eV） ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV±30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a - 1 MA facility.

Simulations on the multi-shell target ignition driven by radiation pulse in Z-pinch dynamic hohlraum

We present the first simulation results of a multi-shell target ignition driven by Z-pinch dynamic hohlraum radiation pulse.The radiation pulse is produced with a special Z-pinch dynamic hohlraum configuration,where the hohlraum is composed of a single metal liner,a low-Z plastic foam,and a high-Z metallic foam.The implosion dynamics of a hohlraum and a multi-shell target are investigated separately by the one-dimensional code MULTI-IFE.When the peak drive current is 50 MA,simulations suggest that an x-ray pulse with nearly constant radiation temperature(-310 eV)and a duration about 9 ns can be obtained.A small multi-shell target with a radius of 1.35 mm driven by this radiation pulse is able to achieve volumetric ignition with an energy gain(G)about 6.19,where G is the ratio of the yield to the absorbed radiation.Through this research,we better understand the effects of non-uniformities and hydrodynamics instabilities in Z-pinch dynamic hohlraum.