用于Z箍缩诊断装置的快阀研制

Z箍缩实验滞止后期负载产生的微小碎片及其他飞溅物质会污染Z箍缩诊断系统内的光学器件,本文研制了一种基于电磁感应原理的快阀,其可用于遮断微小碎片及其他飞溅物质。根据能量守恒和电路方程,计算了快阀的运动速度、遮断时间及线圈放电电流等参数,并利用实验测量获得快阀运动速度为19 m/s,遮断时刻时间抖动为85 μs,实验测量与计算结果较为吻合。     

金属丝阵列Z箍缩装置中R-T不稳定性初步研究

近年来,对金属丝阵列Z箍缩的研究引起了Z箍缩物理界的极大兴趣。在这种位形中,能产生高密度和高温度的等离子体,甚至可能达到聚变条件。然而,等离子体内爆(Implosion)却受到R-T不稳定性的严重影响,因为等离子体受到无质量流体磁场的加速。Z箍缩内爆的效率主要取决于内爆的对称性和均匀性。但是,各种增加负载轴向和极向对称性的尝试用于减弱Reighlay-Taylor(R-T)不稳定性,只     

Z箍缩X射线源辐射场理论分析

利用Z箍缩等离子体辐射源产生X射线可开展脉冲X射线辐照材料动力学响应及热力学效应研究,而试验面处的辐射功率密度是热力学效应研究中最关心的参数。本文针对Z箍缩产生的软X射线辐射功率密度场分布,以理论分析和数值模拟为手段,将Z箍缩软X射线辐射源分别等效为线光源和朗伯辐射光源,获得了2种等效情况下X射线辐射功率密度场的分布。分析表明,在线光源等效情况下,远场分布为球面分布,符合距离平方反比关系,而近场则近似圆柱面分布,符合距离反比关系;在朗伯辐射光源等效情况下,远场分布为球面余弦调制分布,而近场分布近似圆柱面分布。等效模型分析结果均表明：对于长度为2 cm的Z箍缩软X射线辐射体,当试验样品放置位置距离Z箍缩光源大于5 cm后,试验面处的辐射功率密度即可视为远场情况,符合距离平方反比关系。     

Z箍缩强X射线源金属丝阵列负载

惯性约束聚变(ICF)运用强的能量介质轰击聚变燃料而实现聚变点火,具有明显的军事应用背景。作为ICF研究途径之一,Z箍缩装置在近年的实验中产生的X射线辐射的功率P_(x-ray)和能量E_(x-ray)均取得了突破性进展,得到了国际社会的广泛关注。1997年在美国Sandia国家实     

用于Ｚ箍缩的双层喷气负载设计

双层喷气负载作为减小瑞利-泰勒不稳定性的重要手段,在Z箍缩实验中得到广泛应用。本文主要阐述双层喷气负载的机械设计,包括整体结构以及密封、同步等。分析了影响内外气室气密性的主要因素及弹簧参数的选取。对由线圈、铁芯及拉杆组成的拉阀系统进行了验算。结果表明,在所选参数下,系统完全满足实验要求。最终在“强光一号”加速器上进行了结构验证性实验,获得了满意的效果。     

Wire-array Z箍缩工程与实验介绍

近年来,Z箍缩采用金属丝阵列作为负载用以产生超强X射线并已取得了令人鼓舞的成果。采用惯性约束聚变方式,这要的X射线可以点燃聚变燃料。采用这种方法获得的X射线在其他领域也有广泛的应用前景并已在国外装置上开展了相关的应用研究实验。金属丝阵列由20～300根柱状对称的金属丝组成,阵列长度为1～2cm,半径为8～20cm。金属丝采用W,     

漂移热流与托卡马克等离子体径向箍缩

考虑到俘获粒子的极向分布不均匀性,在研究可能的等效外场引起的径向输运时,本文分析了漂移热流的影响。由于磁场的不均匀性,漂移热流可使磁面上离子平衡温度不再为常量,从而导致沿磁力线方向静电场的出现。当考虑到俘获粒子效应时,这种沿磁力线电场引起的粒子径向箍缩是一种新经典类型的箍缩机制。在反磁剪切引起的势垒处,由于温度梯度特别大,这一箍缩效应极为强烈,这有助于解释此处输运好于新经典输运的原因。     

环向非对称ICRF波情形下的波感应粒子箍缩的证据

在联合欧洲环（ＪＥＴ）的近轴高功率环向非对称ＩＣＲＲ（离子回旋频率范围）加热的实验中，首次观察到了射频（ｒｆ）波感应捕获离子的粒子箍缩。当波的方向在相反的环向时，放电中探测到了明显的差异。特别是发现快离子驱动的阿尔芬本征模活性、锯齿行为和质子分布函数受到强烈的影响。大量的放电分析表明，所观测到的差异与理论预言的ＩＣＲＦ感应粒子箍缩是一致的。     

Rod-pinch二极管箍缩特性的数值模拟

采用UNIPIC程序模拟Rod-pinch二极管(RPD)的工作过程,重点研究阳极等离子体和二极管结构参数对电子束箍缩的影响。模拟结果表明,在不考虑阳极离子流作用情况下,RPD无法在较低电压下(2MV)实现箍缩;当阳极离子流达到一定值后,进一步增加阳极表面发射离子流密度对二极管总电流和阳极杆尖端电流密度影响很小;阴极不同表面发射电子束的箍缩效果不同,各表面同时发射电子时,后表面发射的电子束箍缩效果最好,其次是中间表面,前表面最差;增大阴极厚度不能显著缩短电子束实现箍缩的时间。给出了阳极杆伸出阴极平面距离和阴阳极半径比等参数的选取范围,对模拟计算与实验结果间的偏差作出了解释。     

兆安级电流下Al丝阵的芯晕结构抑制研究

为了抑制丝阵Z箍缩中金属丝在电流早期电爆炸形成的芯晕结构,基于强光一号加速器,利用二级丝阵负载开展了Al丝阵早期物理状态的调控研究。通过陡化预脉冲和调整二级丝阵的参数,实现了负载Al丝的全部汽化,抑制了芯晕结构的产生,气态Al丝芯的平均直径约为1.80 mm,且沿轴向均匀分布,降低了丝阵消融引起的初始不稳定性。若丝长度和直径保持不变,反转型丝阵的关断时间主要取决于Al丝的丝数;反转型丝阵关断后,气态丝芯在主电流脉冲作用下迅速电离并开始内爆,磁瑞丽泰勒不稳定性迅速发展,内爆等离子体流沿轴向呈周期性调制分布,调制波长约为650 μm。Al丝阵初始状态的改变,有效抑制了丝的消融过程,消除了先驱等离子体,在内爆后期降低了拖尾质量,提高了箍缩品质。     

Al丝物理状态调控及对芯晕演化特性的影响

基于快直线脉冲变压器(FLTD)平台开展了数十kA电流下Al单丝芯晕演化特性研究,实验发现丝过早发生电压击穿会减少丝芯的能量沉积,而晕等离子体的迅速发展将约束丝芯的进一步膨胀,降低丝芯膨胀速度。通过调整负载两端的初始电压、丝长及增加闪络开关等手段,抑制了Al丝的过早击穿,增加了早期能量沉积,获得了不同的丝芯物理状态（部分气化或完全气化）。Al丝的气化提高了丝芯膨胀速度,最高达11~14 km/s,晕等离子体发展缓慢,延缓了边界处不稳定性的出现,降低了后期m=0的发展速度。FLTD负极性输出时,Al丝沿轴向的极性效应更加明显,靠近阴极处丝芯膨胀慢,边界处晕等离子体密度高,不稳定性的发展速度快。     

Preparation of ultrafine tungsten wire via electrochemical method in an ionic liquid

Ultrafine tungsten wire less than 10 μm in diameter is often used as wire array load applied in Inertial Confinement Fusion (ICF) physical experiments. In order to obtain a higher yield of X-ray, both initial radius and line quality of metal wire were required to be of high quality simultaneously. This paper has studied the electrochemical method to corrode tungsten wires uniformly in an ionic liquid electrolyte containing 1 wt% sodium hydroxide. A three electrode system composed of a tungsten anode electrode, a stainless steel cathode and a saturated calomel electrode as a reference electrode, was used in the electrochemical experiments. Liner sweep voltammetry (LSV) and Tafel experiments were used to investigate the electrochemical behaviors of tungsten wires in ionic liquid and aqueous solution. Based on scanning electron microscope (SEM) observation, the morphologies of tungsten wire surface with uniform corrosion under different applied voltages have been demonstrated. X-ray diffraction (XRD) methods were employed to track the evolution of the crystal structure before and after corrosions, and there is an obvious difference in peak intensities. The ultrafine tungsten wire with a uniform diameter of 8.5 μm was obtained under the optimized electric potential (2.5 V) applied for decreasing diameter at 30 °C.     

超细钨丝连续电解抛光工艺参数优化

以直径低于10μm的超细钨丝作为Z-pinch实验丝阵负载材料,其制备常用到电解腐蚀技术。为定量控制每道次钨丝的减径量,并探索钨丝电解参数优化方法,根据法拉第定律推导并验证了在应用电解腐蚀技术制备超细钨丝的过程中单位长度钨丝的失重与电流强度和拉丝速率的比值存在正比关系。实验观测到,道次减径比超过25%时,断丝几率较减径比为20%时的高60%以上。基于实验结论,提出了每道次定量控制钨丝直径减少量的方法。在18～26℃、质量分数为15%的KOH溶液中,针对3μm钨丝采用了最小化腐蚀道次的电解参数。对用这种参数制得的钨丝进行SEM和力学性能测试,结果表明,钨丝表面质量与断裂强度更好。     

Distance for fragmentation of a simulated molten-core material discharged into a sodium pool

A series of experiments has been carried out to obtain experimental knowledge on the distance for fragmentation of a molten core material discharged into the sodium plenum during postulated core disruptive accidents of sodium-cooled fast reactors. In the current experiments, 0.9 kg of molten aluminum (initial temperature: around 1473 K) was discharged into a sodium pool (diameter: 0.11 m, depth: 1 m, initial temperature: 673 K) through a nozzle (inner diameter: 20 mm). Visual observation of the fragmentation behavior was performed using an X-ray imaging system. The following experimental results were obtained. (1) Liquid column of molten aluminum was intensively fragmented almost simultaneously with a rapid expansion of sodium vapor in the vicinity of the column. (2) Due to the intensive fragmentation, penetration of the liquid column was limited to approximately 100 mm or so from the sodium level. (3) The molten aluminum was rapidly cooled after the intensive fragmentation. Based on these results, the distance for fragmentation of the liquid column was estimated to be 100 mm in the experiments. Through the current experiment, useful knowledge was obtained for the future development of an evaluation method of the distance for fragmentation of the molten core material.     

Expansion of Plasma of Electrically Exploding Single Copper Wire Under 4.5kA～9.5kA/Wire

Abstract The experimental system for electrically exploding single metal wire has been de-signed and manufactured. Expansion of the dense plasma column formed from an electricallyexploding Cu wire of diameter 30 μm has been studied with a high-speed photographer to obtainthe time-dependent radius (R-t) curve. The experimental results demonstrate that the mean ex-pansion rate of the dense plasma column is 1.94 μm/ns, 2.6 μm/ns and 3.75 μm/ns according tothe peak pulse current 4.5 kA, 7 kA and 9.5 kA respectively. The results can be beneficial to givinga profound understanding of the early stage of wire-array Z-pinch physics and to improvement ontheir design.     

超短超强激光与不同厚度的铝膜作用加速质子的实验研究

介绍了功率密度4×10¹⁶W/cm²,脉宽120 fs情况下超短超强激光分别与5和2.1 μm薄膜铝靶作用加速质子的实验。采用CR-39固体径迹探测器和Thomson谱仪结合测量得到质子能谱,并对实验结果进行分析。测得的5 μm铝靶的质子最大能量约为140 keV,2.1 μm铝靶的质子最大能量约为170 keV。2.1 μm铝靶的质子产额较5 μm铝靶的高1个量级。     

A nanoparticle formation model considering layered motion based on an electrical explosion experiment with Al wires

To study the evolution of nanoparticles during Al wire electrical explosion, a nanoparticle formation model that considered layered motion was developed, and an experimental system was set up to carry out electrical explosion experiments using 0.1 mm and 0.2 mm Al wires. The characteristic parameters and evolution process during the formation of nanoparticles were calculated and analyzed. The results show that the maximum velocities of the innermost and outermost layers are about 1200 m·s−1 and 1600 m·s−1, and the velocity of the middle layer is about 1400 m·s−1, respectively. Most of the nanoparticles are formed in the temperature range of 2600 K‒2500 K. The characteristic temperature for the formation of Al nanoparticles is ∼2520 K, which is also the characteristic temperature of other parameters. The size distribution range of the formed nanoparticles is 18 to 110 nm, and most of them are around 22 nm. The variation of saturated vapor pressure determines the temperature distribution range of particle nucleation. There is a minimum critical diameter of particles (∼25 nm); particles smaller than the critical diameter can grow into larger particles during surface growth. Particle motion has an effect on the surface growth and aggregation process of particles, and also on the distribution area of larger-diameter particles. The simulation results are in good agreement with the experiments. We provide a method to estimate the size and distribution of nanoparticles, which is of great significance to understand the formation process of particles during the evolution of wire electrical explosion.     

0.18 μm CMOS电路瞬时剂量率效应实验研究

利用脉冲激光源及脉冲X射线源,开展了超深亚微米CMOS反相器及CMOS静态随机存储器的瞬时剂量率效应实验,测量了CMOS电路瞬时剂量率效应,并与微米级电路的瞬时剂量率效应进行了比较。结果表明,对于CMOS电路,特征尺寸的缩小对其抗瞬时剂量率性能的影响与电路的规模有关。0.18 μm CMOS反相器的抗瞬时剂量率性能远优于微米级反相器,而0.18 μm CMOS静态随机存储器的抗瞬时剂量率性能远低于微米级及亚微米级存储器。     

Thermal Shock Behavior of SiC Coatings for Fusion Reactor Applications

Graphite substrate ISEM-3 whose thermal expansion coefficient is close to that of SiC and graphite substrate AXF-5Q1 whose thermal expansion coefficient is larger than that of SiC were coated with 50–200 μm thick CVD-SiC. On the AXF-5Q1 graphite substrate SiC could not be completely coated. Additionally HSC-SiC, which has SiC conversion layer of 800 μm thickness and whose thermal expansion coefficient of the graphite substrate is close to that of SiC, was also tested. Thermal shock test was carried out by electron beam of accelerating voltage of 10 kV, beam current of 50–200 mA, beam diameter of about 10 mmø and heating time of a single pulse of 30 s. Crack was not observed on the CVD-SiC coating on the ISEM-3 graphite even at 200 mA (about 2.5kW/cm²) and hole of about 1 mm in diameter was observed and the graphite substrate was revealed. Additionally for thermal cycle test (1,000 times, ΔT=950°C), the crack or spalling was not observed on the CVD-SiC coating. It was found that for the HSC-SiC the hole was only observed with the single pulse of 200 mA and the crack was not observed. Thus the HSC-SiC also may be a candidate as the first wall of the fusion reactors.