第十五届全国原子与分子物理学术会议:非局域热动平衡等离子体K壳层电离平衡模型

发展了针对非局域热动平衡等离子体的K壳层电离平衡模型。模型中详细计算了各原子过程参数,并通过求解速率方程的稳态解得到各电离态的布居分布。在此基础之上,研究了谱线强度比值对等离子体温度、密度的依赖关系。最后,我们根据此模型的计算结果,分析了在神光II装置上获得的内爆靶丸掺Ar发射光谱实验数据,推断出靶丸芯区电子温度随时间的演化过程。     

非局域热动平衡等离子体K壳层电离平衡模型

发展了针对非局域热动平衡等离子体的K壳层电离平衡模型.模型中详细计算了各原子过程参数,并通过求解速率方程的稳态解得到各电离态的布居分布.在此基础之上,研究了谱线强度比值对等离子体温度、密度的依赖关系.最后,我们根据此模型的计算结果,分析了在神光Ⅱ装置上获得的内爆靶丸掺Ar发射光谱实验数据,推断出靶丸芯区电子温度随时间的演化过程.     

激光间接驱动内爆靶丸的X光诊断

 报道了神光Ⅱ激光聚变实验中内爆燃料靶丸区电子温度、电子密度以及燃料面密度的X光诊断结果。在电子温度诊断中，采用X射线光谱学方法，根据聚变靶丸燃料区的Ar示踪元素的Ly-β线与He-β线的强度比推断出靶丸燃料区电子温度为(950±100) eV；在电子密度诊断中，利用靶丸燃料区Ar元素的He-β线Stark展宽确定聚变靶丸芯部的电子密度为(0.9±0.2)×10²⁴ cm^-3；在燃料区面密度诊断中，利用X光单能照相技术获得了内爆靶丸的燃料面密度为（3.2±0.5） mg/cm²。     

“神光”Ⅱ内爆动力学研究

2003年“神光”Ⅱ内爆实验中，获得了靶丸燃料区空间分辨的Ar线谱—由此得到Heα等谱线发射区的尺寸，分别由线强比和谱线Stark宽推出了燃料区的电子温度和密度。     

激光应用 激光化学

TL816．1 2006065053激光间接驱动内爆靶丸的X光诊断=X-ray diagnostics of laser indirect-driven implosion pellet[刊,中]/张继彦(中物院激光聚变研究中心,四川,绵阳(621900)),杨国洪…//强激光与粒子束．-2006．18(6)．-939-943报道了神光Ⅱ激光聚变实验中内爆燃料靶丸区电子温度、电子密度以及燃料面密度的X光诊断结果。在电子温度诊断中,采用X射线光谱学方法,根据聚变靶丸燃料区的Ar示踪元素的Ly-β线与He-β线的强度比推断出靶丸燃料区电子温度为(950±100)eV；在电子密度诊断中,     

示踪材料在内爆X光诊断过程中的作用

 激光聚变内爆实验中,在燃料中掺杂少量比例的中高Z材料,用X光光谱和X光成像测量掺杂元素的发射信息,诊断燃料的温度、密度和压缩形状。用辐射流体力学数值计算和X光成像后处理程序综合分析方法,给出了内爆靶丸优化设计,并讨论示踪材料在X光诊断中的作用。结果表明:在靶丸燃料D2中掺原子分数约1.0％的氩,内爆压缩中子产额下降约15％。由于氩线发射使整个燃料区X光发射强度提高约50倍,X光成像区域增大约30％,有利于实验诊断测量燃料芯部。为了测量燃料区的边界,在CH内壳层涂厚度0.05 μm的硫,分析表明硫Ly-α单能成像大小与流体力学计算的燃料区大小一致,可用于诊断燃料最终压缩界面。数值分析结果得到了神光Ⅱ间接驱动内爆物理相关实验的验证。     

间接驱动内爆靶丸示踪元素Ar发射X光谱线的理论模拟研究

惯性约束聚变内爆物理研究中, 示踪元素X光谱线诊断方法是推测内爆压缩温度、密度以及燃料混合的有效办法, 因此, 对示踪元素X光发射的规律及其与内爆过程的关系的研究非常必要, 有助于通过谱线发射特征诊断内爆状态. 以SGIII原型装置的实验条件下的内爆过程为例, 对内爆靶丸示踪元素Ar发射X光谱线进行了理论模拟. 研究了谱线自吸收效应、Ar掺杂浓度、等离子体空间分布不均匀等对Ar发射的X光谱线分布的影响. 还对Ar发射X光谱线强度的时间演化及其与内爆过程的关系进行了研究. 结果表明, 增加掺杂浓度, 谱线强度增强, 但是谱线自吸收效应的影响也明显增强. 示踪元素Ar发射的X光谱线强度的峰值时刻与中子产生速率的峰值时刻接近(前者延迟约15 ps). 高温、高密度及合适的电离度是谱线发射的3个条件, 在X光谱线发射的峰值时刻, 由于燃料芯部Ar等离子体过电离, Ar等离子体发射的X光谱线的空间峰值区域靠近燃料边界区域, 占燃料总体积56%的薄壳(厚度～4 μm), 其发射的X光谱线强度约为总强度的72%. 因此, 对发射谱线分布拟合得到的空间平均的等离子体温度、密度主要反映这一区域的等离子体状态.     

间接驱动的内爆不对称性随腔长和时间变化的研究

在激光间接驱动惯性约束聚变中, 为达到高密度压缩以实现点火, 对靶丸内爆对称性和黑腔辐射场均匀性有严格的要求. 为了研究内爆不对称性随腔长和时间的变化, 实验中采用了三种不同尺寸的黑腔, 利用X光分幅相机观测了靶丸燃料区自发光, 获得了压缩变形过程和椭圆度变化规律, 初步判断了在三种腔型中腔长1700 μm 的黑腔较接近神光Ⅲ原型装置内爆对称性要求. 根据视角因子程序计算得到辐射流不对称性随时间变化情况, 通过一个简化的解析模型推导出内爆形变不对称性随时间变化过程, 与实验结果大致符合. 由此进一步分析了黑腔辐射场不均匀性的演化导致内爆不对称性随腔长和时间变化的物理机制. 关键词： 内爆不对称性 黑腔辐射场不均匀性 腔长 视角因子程序     

靶丸燃料容器制备技术

2003年，多层空心塑料微球的研制取得了实质性进展。具有聚苯乙烯-聚乙烯醇-CH烧蚀层结构的3层塑料微球首次用于“神光”Ⅲ物理实验，取得了较为满意的结果：获得了靶丸燃料区空间分辨的Ar线谱——得到Heα等线谱发射区的尺寸；利用针孔(分幅相机)、环孔诊断获得了靶丸芯部发光区图像。     

神光Ⅱ装置靶丸内爆过程X射线背光照相实验研究

在神光Ⅱ装置上,8路激光注入金柱腔靶产生X射线驱动位于柱腔中心的DD靶丸内爆,第9路激光辐照Pd背光靶产生的L线X射线透视内爆靶丸,用针孔成像方式获得靶丸的透视图像,高速X射线条纹相机记录靶丸透视图像,建立了间接驱动内爆靶丸背光照相的实验方法,清晰地观测到了靶丸内爆的过程,对透视图像分析获得了内爆靶丸壳层运动轨迹和速度的实验数据,所获实验结果可用于间接驱动靶丸优化设计,还可用于内爆动力学数值模拟建模和计算结果的验证。     

Emission spectrum from an Al/Mg tracer in the blow-off region of a radiatively ablated capsule

A study of X-ray emissions from Al/Mg tracers buried at two different depths in a plastic shell is presented. The X-rays originating from the K-shell transitions of the Al/Mg ions begin to irradiate after the ablative heating wave has passed through the trace layer and are recorded with a streaked crystal spectrometer. Only emissions from the capsule with the trace layer buried at a smaller depth are observed. Hydrodynamic simulations and a collisional—radiative model including detailed atomic physics are used to investigate the measured spectrum. It is found that the effects of the radiative heating play important roles in the formation of the K-shell emission. The time correlation between the simulations and the measurements is obtained by comparing the measured time profile of the He α emission with the calculated one. The line ratio of Ly α to He α is also calculated and is found to be in fairly good agreement with the experimental data. Finally, the relation between the time profile of the He α emission and the ablation velocity is also discussed.     

Microfield fluctuations and radiative transitions in laser-generated strongly coupled plasmas

Previously unaccessible plasma states of matter can be produced by irradiation with powerful lasers. The interactions within the plasma shift and distort the spectral lines corresponding to radiative transitions. The shape of the spectra is determined by two frequencies characterizing the fluctuations of the electric microfield in the plasma and the Stark splitting of the lines. Traditionally the fluctuations due to the motion of the ions are considered as sufficiently slow and weak to be treated in a linear quasi-static approximation, while the electrons are accounted for in an instantaneous impact approximation. Here also the intermediate regimes and strongly correlated ions are investigated. For that purpose the microfield fluctuations are calculated by molecular dynamics computer simulations. They are then used as input in a numerical solution of the time-dependent Schrödinger equation for the radiating electron. The shape of the Ly -line in H and in Al is investigated in the intermediate regime. The calculations are in agreement with recent experiments on the Ly and Ly lines in Al.Received: 7 January 2004, Published online: 15 April 2004PACS: 32.30.Rj X-ray spectra - 32.70.Jz Line shapes, widths, and shifts - 52.25.Os Emission, absorption, and scattering of electromagnetic radiation - 52.65.Yy Molecular dynamics methods     

时间分辨晶体谱仪在Z箍缩等离子体中的应用

在装置阳加速器上,使用椭圆弯晶谱仪对Al丝阵Z箍缩实验的X射线辐射特性进行了研究。在谱仪结构中,使用椭圆面的晶体作为分光元件,采用PIN阵列作为记录元件实现时间分辨测量,同时用成像板记录时间积分结果。在Al丝阵Ｚ箍缩实验中,获得了时间分辨的Al等离子体Ｋ壳层辐射谱,用基于碰撞-辐射模型的K壳层线辐射谱分析程序对Al丝阵Z箍缩的实验数据进行了分析,获得了Al丝阵等离子体的时间分辨的电子温度和时空平均的电子数密度参数。     

Sodium satellite structure

A sample of sodium was bombarded by proton, helium, and oxygen beams and the subsequentK X-ray spectra measured. The spectra exhibit a preponderance of structure which is speculated upon in light of HFS calculations. The strongest lines are ascertained to be the normalKα satellite spectra produced by multiple electron vacancies in single ion-atom collisions.     

实验室晶体积分衍射效率标定方法研究

基于X射线衍射仪运行的稳定性和角度的精密控制能力,以平面季戊四醇(PET)晶体为样品,对晶体的积分衍射效率标定方法进行了实验研究。实验的光源是Cu靶X射线管,通过适当选取镍滤片和精细控制管电压,极大地抑制了Kβ线谱和韧致辐射,实现了Kα线能量单色化。正比计数器前端的狭缝是0.05mm,采用0.001°的步进角度对源强和Kα线衍射峰分别进行扫描。数据处理后得出在Cu的Kα线能点(8047.823eV)处,该平面PET晶体的积分衍射效率是(1.759±0.002)×10-4 rad。实验结果表明该方法可以在实验室条件下快速、方便地完成平面晶体积分衍射效率的标定。     

Experimental evidence for strong plasmon coupling in the soft X-ray appearance potential spectrum of graphite

Plasmon satellite structure is known to be weak in X-ray absorption experiments because of the effective cancellation between the couplings to the conduction electrons of the excited electron and core hole. Data on the soft X-ray appearance potential spectrum for the K-shell excitation of graphite however are shown to exhibit strong plasmon effects illustrating the enhanced coupling that results from the creation of an additional conduction electron.     

He and Ar post-bombardment effects on carbonitrides formed in a Cr-rich steel

The effects of He and Ar bombardment on carbon produced in a N-implanted Cr-rich steel are studied by means of conversion electron Mössbauer spectroscopy, glancing X-ray and nuclear reaction analysis techniques. The results show two main features: dissolution and reprecipitation of the produced carbonitrides and modification of the thermal behavior of the precipitates. Comparison with similar experiments performed on Fe and on low-carbon steel show that the matrix composition plays an important role in the above processes.     

Experimental core-hole ground state energies for the elements 41Nb to 52Te

Photoelectron spectra from metallic systems always show asymmetric core lines. One effect of this asymmetry is to shift the peak position of a core level spectrum away from the ground state energy of the core hole state. In this letter, M and N core level binding energies for the 5th period elements are reported which have been corrected for the effect of the asymmetry. In some cases the relative energy positions have been compared to accurate X-ray data. The results indicate that even when fairly broad core electron lines are involved, accurate core level separations can be determined.     

靶材料杂质影响新谱线产生的实验验证

 为了验证氢气放电源打靶产生的新谱线不是靶杂质的特征谱线,完成了5项检验实验。其中屏蔽实验和强电子辐照靶的实验证实了新谱线不是来自放电室中的杂质形成的;靶的打磨实验表明靶表面的污染杂质也不能产生新谱线,形成共振峰的实验和新谱线强度随放电电压变化规律的实验结果都证明靶的总杂质不影响新谱线的测量。     

Electron density in Si2 and Cl2

Self consistent field-Xα molecular orbital calculations have been performed for Si₂ and Cl₂ using both the scattered-wave (SW) and LCAO discrete-variational (DV) versions of the method. For Si₂ an SW calculation including f partial waves yields orbital densities in good agreement with those from methods which do not involve the muffin-tin approximation for the potential. The present results afford a further comparison relevant to the recent discussion (see, M. Schlüter et al. [9]) of the relative accuracy of various pseudocharge densities compared with real charge densities. The deformation density from the Xα-SW calculation is in good agreement with that from the DV-Xα method and also with that from the linear muffin tin orbital method (J. Harris and R. O. Jones [8]). Differences between the valence electron distribution which is usually discussed in connection with pseudopotential schemes, and the density distribution including the 2s and 2p core electrons are delineated. For Cl₂, the Xα-SW deformation density shows positive lobes along lines through the atoms perpendicular to the bond axis, is negative for most of the area between the atoms and also shows negative lobes behind the atoms. This deformation map is in good qualitative agreement with the DV-Xα map and also with recent ab initio results with the exception of a small region at the centre of the bond in which the DV-Xα and ab initio results show an excess of electrons compared with the promolecule whereas the Xα-SW results show a deficiency. Comparisons with X-ray results on solid chlorine are inconclusive so that experimental electron scattering data on gas phase chlorine will be required to resolve this difference.