丝阵Z箍缩可见光辐射区径向变化过程

 在“强光一号”上进行的Z箍缩实验中,利用1维可见光成像系统获取了丝阵内爆可见光辐射区径向变化过程图像。采用的负载包括单层钨丝阵、单层铝丝阵,驱动电流为1.3~1.5 MA,上升时间89~140 ns。实验结果表明:丝阵内爆产生轴向先驱等离子体柱,尺寸为0.3~0.5 mm;丝阵在内爆和内爆到芯及冷却飞散阶段,外围区域始终存在较弱的可见光辐射;获得的可见光条纹像提供了丝阵等离子体内爆可见光轨迹,内爆径向压缩比为2.84～7.84,丝阵内爆速度为4.60×10⁶～1.73×10⁷ cm/s。     

用离焦4f差分干涉仪测量等离子体壳层电子密度

 将环型横向剪切干涉仪置于两个镜头之间,由此设计出一种新型的离焦4f差分干涉仪,该干涉仪同时具有分离光路的剪切量和条纹空间频率分别可调的优点以及共光路结构的稳定性和易于调节的优点,使得在测量大密度梯度等离子体的密度分布时,可以在不降低空间分辨率的条件下仍保证干涉条纹可读。在DPF装置上进行了实验,获得了等离子体壳层的干涉图样,计算了等离子体的径向电子密度分布,在内电极端面上方测量到的最高电子密度约为1.2×10¹⁹ cm^-3,外围等离子体壳层的电子密度约为2×10¹⁸ cm^-3。     

激光等离子体脉冲软X光标定源

 利用神光Ⅱ上激光与等离子体相互作用得到的软X光,建立了基于多层镜的四通道软X光单色器系统。研究了光源的性能,测量了光源强度、单色器系统稳定性、相应通道的一致性。研究表明,采用多层镜作为脉冲光源的分光元件,可以得到具有较好单色性的强脉冲软X 光标定源。光源的光子能量为253 eV和820 eV,两能道的光源强度分别为1.8×10¹⁹ photon/(s·cm²)和3.2×10¹⁹ photon/(s·cm²)。在该标定源上可以实现XRD、平面镜、多层镜、透射光栅和滤片的标定。     

TiGen-(n=7~12)团簇的光电子能谱及密度泛函理论研究

利用光电子能谱及密度泛函理论计算对TiGe_n^-(n=7~12)团簇的几何结构及电子特性等进行了系统研究. 对于TiGe_n^-负离子及中性TiGe_n,在n=8时出现了钛原子半内嵌的船型结构;在n=9~11时,新增的锗原子加盖到这种船型结构上,逐步形成钛原子完全内嵌的结构. TiGe₁₂^- 团簇具有一种钛原子内嵌的变形六棱柱结构. 自然布居分析结果显示,对于n=8~12的TiGe_n^-/0 团簇,随着内嵌结构的形成,有电子从锗原子转移到钛原子,说明其电荷转移方式与结构演变密切相关.     

高通量中性原子氧束流的发生与控制

 采用微波同轴耦合氧气放电产生高密度氧等离子体, 经磁场约束后与一施加负偏压的金属板碰撞复合并反射, 得到通量在10¹³~10¹⁶atom/cm²×s范围可控, 动能约为6-10eV的中性氧原子束流。用双探针技术对生成的氧等离子体进行了诊断测量。根据聚酰亚胺在原子氧作用下的剥蚀率对原子氧束流进行了标定测量。     

射频电感耦合夹层等离子体中的模式转换

本文利用微波相位法和光谱诊断法, 研究了ICP放电等离子体在圆台状夹层等离子体中E模和H模相互转换的物理现象. E模和H模的之间转换过程是一个瞬间突变的, 转换点的输入功率随真空室压强的变化而变化. H模向E模转换的阈值功率低于E模向H模转换的值, 等离子体参数随输入功率变化曲线类似于铁磁物质中的磁滞回线. Ar II 408.2 nm谱线的强度的变化规律和电子密度随功率变化的规律基本一致. 通过本实验可以获得一种电子密度范围为3.85×10¹¹ cm^-3 < n_e < 4.68× 10¹¹ cm^-3, 外表面积为0.3 m², 厚度为2 cm稳定工作的等离子体源.     

超强激光与Ar团簇相互作用中X射线的研究

本文主要研究了超强超短激光与Ar团簇相互作用过程中X射线能谱、K壳层光子产额、能量转换效率以及激光对比度对X射线光子产额的影响.实验中得到K壳层的光子产额约为1× 10¹¹/发,能量转换效率约为2.8× 10^-5．同时观测到较强预脉冲离化团簇会导致预电离,产生膨胀等离子体,然而主脉冲与膨胀的等离子体相互作用的强度较未膨胀时降低了,从而导致K壳层光子产额降低,而使用高对比度的激光能增加X射线光子产额.     

氧氩比对SnO2/Ag/SnO2透明导电膜光电性能的影响

在室温及不同的氧氩比条件下,采用射频磁控溅射Ag层和直流磁控溅射SnO₂层,在载玻片衬底上制备出了SnO₂/Ag/SnO₂多层薄膜.用霍尔效应测试仪、四探针电阻测试仪和紫外-可见-近红外光谱仪等表征了薄膜的电学性质和光学性质.实验结果表明:当氧氩比为1:14时,所制得的薄膜的光电性质优良指数最大,为1.69×10^-2 Ω^-1;此时,薄膜的电阻率为9.8×10^-5 Ω·cm,方电阻为9.68 Ω/sq,在400~800 nm可见光区的平均光学透射率达85%;并且,在氧氩比为1:14时,利用射频磁控溅射Ag层和直流磁控溅射SnO₂层在PET柔性衬底上制备出了光电性质优良的柔性透明导电膜,其在可见光区的平均光学透过率达85%以上,电阻率为1.22×10^-4 Ωcm,方电阻为12.05 Ω/sq.     

对超短脉冲激光引雷产生的等离子体通道的特性分析

 利用隧道电离诱导闪电模型,对超短脉冲激光在大气中产生弱等离子体通道的电阻和阈值强度进行了分析和计算。结果显示：强度为10¹⁴ W/cm²量级的超短脉冲激光产生的气体等离子体通道有较好的导电性,所需激光能量很小, 说明在该模型下激光能量的利用效率很高。     

真空中微波等离子体喷流电子数密度分布规律实验研究

为了准确诊断真空中微波等离子体喷流的电子数密度，利用统一的发射和单郎缪尔探针测量等离子体的空间电位，再测量等离子体的电流-电压特性曲线.根据空间电位测量结果，在等离子体的电流-电压特性曲线上能准确地获取饱和电流，从而处理出电子数密度.最后的诊断实验表明，当真空环境压强为2—6 Pa、等离子体发生器以60 W以下的微波功率击穿流量范围是42—106 mg/s的氩气时，所产生的微波等离子体喷流中电子数密度分布在1×10¹⁶—7.2×10¹⁶/m³范围内.     

高密度氩等离子体电子密度的计算

用屏蔽氢离子模型计算了冲击压缩产生的温度T～2.0eV、密度ρ～0.01g/cm3～0.49g/cm3范围内氩等离子体的电子密度,探讨了不同温度、密度范围内的高密度氩等离子体中粒子之间相互作用对电子密度的影响.     

Analysis of hydrogen adsorption in the bulk and on the surface of magnesium nanoparticles

The stability of magnesium hydride (MgH _x ) nanoparticles (x = 0.5, …, 2) is investigated using ab initio calculations. It is shown that for a nanoparticle diameter of D ～ 5 nm, the internal pressure becomes lower than 3 kbar; for this reason, the structure of hydride nanoparticles coincides with the structure of this hydride in crystalline form. It is found that the phase of partly saturated MgH _x hydrides (x < 2) must decompose into the phase of pure hcp magnesium and the α phase of MgH₂. The frequencies of jumps of hydrogen atoms within the hcp phase of magnesium and in the α phase of MgH₂ are calculated; it is shown that slow diffusion of hydrogen in magnesium is due to the large height of potential barriers for motion of hydrogen within MgH₂. To attain high diffusion rates, the structures of Mg₅₃Sc and Mg₅₃Ti crystals and their hydrides are calculated. It is found that the frequency of jumps of H atoms in Mg₅₃ScH₁₀₈ near the Sc atoms does not noticeably change as compared to the frequency of jumps in the α phase of MgH₂, while the frequency of jumps in Mg₅₃TiH₁₀₈ near Ti atoms is higher by approximately a factor of 2.5 × 10⁶. This means that diffusion in manganese hydride with small admixtures of titanium atoms must be considerably eased. Chemical dissociation of hydrogen molecules on the (0001) surface of hcp magnesium, on the given surface with adjoined individual Ti atoms, and on the surface of a one-layer titanium cluster on the given surface of magnesium is investigated. It is found that dissociation of hydrogen at solitary titanium atoms, as well as on the surface of a Ti cluster, is facilitated to a considerable extent as compared to pure magnesium. This should also sharply increase the hydrogen adsorption rate in magnesium nanoparticles.     

Rotating relativistic electron beam-plasma interaction and formation of a field-reversed configuration

Experimental results on interaction of a rotating relativistic electron beam with plasma and neutral gas are presented. The rotating relativistic electron beam has been propagated up to a distance of 150 cm in a plasma. The response of the plasma to the rotating electron beam is found to be of magnetic diffusion type over a plasma density range 10¹¹–10¹³ cm⁻³. Excitation of the axial and azimuthal return currents by the rotating beam and subsequent trapping of the azimuthal return current layer by the magnetic mirror field are observed. A field-reversed configuration has been formed by the rotating relativistic electron beam when injected into neutral hydrogen gas. We have observed field reversal up to three times the initial field in an axial length of 100 cm.     

An in situ neutron diffraction measurement of the pressure–temperature evolution of a MgD2:TiD2 mixture

The hydrogen storage capacity of Mg–Ti–H films is approximately five times that of conventional metal hydride electrodes in NiMH-batteries. Mg and Ti are considered to be immiscible in the bulk and the ambient pressure phase diagram of Mg and Ti indicates that no binary stable bulk compounds are formed. However, in the presence of hydrogen, an Mg–Ti–H phase has been obtained by Kyoi et al. using a high pressure synthesis – where magnesium hydride is compacted with different TM-hydrides in an anvil cell at pressures of the order several GPa (4–8 GPa) and at a temperature of 873 K. In this work, we have proved the feasibility of in situ powder diffraction using the Paris–Edinburgh high pressure cell for the observation of structural changes on this system and we propose modifications to improve the output of the experiment.     

HT-7超导托卡马克调制电流改善等离子体约束

 在HT-7超导托卡马克上进行了电流调制改善等离子体约束物理实验，获得了初步的实验结果。对电流调制时的径向电场进行了数值计算和讨论。当等离子体环向电流以适当的频率和幅值周期性调制时，低模数的磁流体不稳定性得到明显的抑制，等离子体中心电子温度增加了33%，等离子体电子密度分布明显陡化，能量约束时间增加了27%~45%。杂质辐射周期性减少,粒子约束时间增加了2倍。在等离子体边界产生更强的径向负电场。     

高功率微波窗内外表面闪络击穿流体模拟研究

建立理论模型,将电磁场时域有限差分方法与等离子体流体模型结合,编制一维电磁场与等离子流体耦合程序,数值研究了3 GHz高功率微波窗内外表面闪络击穿的不同物理过程.研究结果表明:外表面闪络击穿中,输出微波脉宽缩短(未完全截止),窗体前均方根场强呈驻波分布,波节与波腹位置不变,窗体外表面形成有一层高密(约10~(21)·m~(-3)量级)极薄(约mm量级)等离子体(扩散缓慢),入射波可部分透过该薄层等离子体,脉宽缩短主要源于等离子体吸收效应;降低初始等离子体密度、厚度、入射波场强及缩短入射波脉宽等方式,可不同程度地改善输出脉宽缩短效应.内表面闪络击穿中,窗体前均方根场强亦出现驻波分布f但波节与波腹位置随时间变化),等离子体向波源方向运动;强释气下,输出脉宽缩短(未完全截止),形成多丝状高密(约10~(21)·m~(-3)量级)极薄(约mm量级)等离子体区域(扩散缓慢),间距1/4微波波长,脉宽缩短主要源于等离子体吸收效应;弱释气、低场强下,脉宽缩短有所改善(但最终截止),形成多带状致密(约10~(18)·m~(-3)量级)略厚(mm-cm量级)等离子体区域(扩散较快),间距1/4波长,脉宽缩短主要源于等离子体吸收效应;弱释气、高场强下,脉宽缩短严重(很快截止),形成块状高密(约10~(21)·m~(-3)量级)较厚(约cm量级)等离子体区域(扩散迅速),脉宽缩短主要源于等离子体反射效应.     

Synthesis of ZnO films with a special texture and enhanced field emission properties

ZnO films with special textures are fabricated on Mo-coated Al₂O₃ ceramic substrates by the catalyst-free electron beam evaporation method, and the as-deposited films are treated by hydrogen plasma. It is found that the surface morphologies of the films are changed significantly after hydrogen plasma treatment and that the films consist of vertically standing and intersecting nanosheets. A lower turn-on field of 1.2 V/μm and an enhanced current density ～0.11 mA/cm² at 2.47 V/μm are achieved. The low threshold field and the high emission current density are attributed primarily to the unique shape and smaller resistivity of the ZnO nanosheet films.     

超短脉冲准分子激光淀积类金刚石薄膜的实验研究

利用ＫｒＦ超短脉冲激光器开展了超短脉冲激光淀积金刚石薄膜实验研究,薄膜生长速率０．０２ｎｍ／ｐｕｌｓｅ,厚度０．５－０．６μｍ,显微硬度５５ＧＰａ,光学透过率优于９０％,采用等离子本的时间－空间分辨的发射光谱技术,给出了等离子体的粒子成份以及等离子体的时间－空间的演化图像,以及在不同激光参数条件下等离子体特性的变化,发现超短脉冲激光的等离子体有能量高、持续时间短（高通量）的特点,适合类金刚石薄膜的     

Anomalously deep penetration of hydrogen and deuterium in assemblies from Nb foils and deuterated polyethylene (CD<Subscript>2</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> under the pulse high temperature hydrogen plasma

Studies of the storage and redistribution of hydrogen atoms under pulse high temperature hydrogen plasma that was obtained using a PF-4 Plasma Focus facility in a multilayered structure (sandwich) which consists of two high-purity niobium foils and a deuterium polyethylene film pressed between them have been carried out using the method for elastic recoil detection (ERD). It was established that, with an increase in pulses of the PF-4 facility, the redistribution of implanted hydrogen atoms for large depths occurs in the two Nb foils and deuterated polyethylene. The depths substantially exceed the projective range of paths of hydrogen ions (at their maximum velocity of ∼10⁸ cm/s). A maximum hydrogen concentration of 45 at % is reached in the nearest surface of the second Nb foil to the PF-4 at 20 pulses of hydrogen plasma. An X-ray diffraction analysis showed the presence of a niobium hydride phase in both Nb foils. The redistribution of deuterium atoms from the bound state of deuterated polyethylene into the near-surface layer and the bulk material of the second Nb foil was detected as well. This phenomenon can be attributed to the transfer of implanted hydrogen atoms through the foil assembly and the transfer of deuterium from deuterated polyethylene into the near-surface layer of the second foil under the effect of powerful shock waves that are created by pulse hydrogen plasma and by acceleration in the diffusion of hydrogen and deuterium in the strain field induced by the shock wave.     

Effect of hydrogen on phase and microstructure of Ti600 alloy

Effects of hydrogen on microstructure characteristics and precipitation behavior have been investigated in Ti600 alloy hydrogenated at 750°C. Due to the precipitation of δ hydride and α″ martensite, X-ray diffraction (XRD) peaks of α phase shifted to lower angles and became broadened. XRD data showed that the addition of hydrogen expanded crystal lattice of α phase and lattice volume increased linearly in the range of 0?C _H?″ martensite and δ hydride. Compared to as-received one, microstructure of hydrogenated Ti600 alloy changed obviously. Equiaxed α phase decreased and even vanished with hydrogen contents increasing. Parallel fine lamellar structure appeared and the colonies were constructed by different orientation. Micro-hardness of hydrogenated Ti600 alloy increased with the increase of hydrogen concentration, and it was considered that interstitial solution strengthening, precipitation of δ hydride, and generation of defects were the major factors.