强场下的Li-like氖复合机制X光激光的数值模拟

论述了隧道电离和阈上电离加热过程。并把此二过程加到一个non-LTE平均原子模型,用此模型来研究强场下光致电离类锂氖复合机制X射线激光。计算结果表明,当驱动激光脉冲为100fs、波长为0.248μm、功率密度为2×10¹⁷Wcm^-2,氖气的密度为10^-3gcm^-3时,类锂氖精细结构跃迁3d_5/2→2p_3/2(λ=98Å)的最大增益系数约为100cm^-1,其维持时间约为1.5ps。     

Enhancement of a 24.77-nm line emitted by the plasma of a boron nitride capillary discharge irradiated by a high-intensity ultrashort laser pulse

Investigations of plasma produced by a boron nitride capillary discharge irradiated with a guided 20-TW Ti: sapphire laser pulse at a peak intensity of 4 x 10(18) W/cm2 are presented. The guided laser radiation in the plasma channel generated He-like ions that, subject to suitable plasma temperature, recombined into Li-like nitrogen ions. Intense radiation at a wavelength of 24.77 nm was observed, indicating possible lasing at the 3d(5/2) - 2p(3/2) transition in Li-like nitrogen.     

类锂硅离子X射线激光谱线宽度和电子密度的空间分布

通过分析类锂硅离子X射线激光谱线宽度的空间分布特性,表明斯塔克展宽是主要的展宽机制;由此得到增益介质电子密度的空间分布显示增益区电子密度约在10¹⁹/cm³左右,对应最大增益处的线宽为0.21?,电子密度为2.9×10¹⁹/cm³。 关键词：     

Recombination scheme in lithium-like ions for X-UV amplification

Recombination in lithium-like ions in a fast cooling plasma is an alternative attractive approach to the X-ray laser because, at a given lasing wavelength, it requires the lowest pumping energy of the main pumping schemes. In this paper we give a status report on recent experiments concerning the Li-like X-ray laser, and we discuss the problem of lengthening of the active medium necessary to obtain a true X-ray laser.     

泵浦功率密度对复合类锂离子X射线激光特性的影响

本文通过分析不同泵浦功率密度下类钾硅离子X射线激光的实验结果以及有可能实现X射线激光的其它类锂离子的光谱特性,表明利用类锂离子复合方案,在现有驱动激光装置上实现“水窗”波段放大器有很大的可能性。     

类Li钙离子精细结构能级和软X射线光谱的理论计算

用多组态HFR方法计算了类Li等电子序列钙(Ca,Z=20)离子1s~2nl(n=2～6,l=0～5)组态的所有能级和电偶极跃迁的软X射线光谱,其中4f→3d,5f→3d及5d→3p、4d→3p由于其下能级跃迁速率较大,容易形成粒子数反转因而可作为激光跃迁,5f→3d、6f→3d跃迁已处于“水窗”波段,而4f→3d的激光跃迁(5.77nm)已为我们最近的实验所证实.并将我们的计算结果与其它理论计算和实验数据进行了比较.     

作为X激光增益介质的激光等离子体特性

本文报道利用具有空间分辨能力的透射光栅谱仪对以三体复合泵浦实现锂离子(Si~(11+)X光自发辐射放大的增益介质——硅激光等离子体特性的研究。结果表明,等离子体5～100A范围软X线辐射主要来自类氦离子(Si~(12+))到(S~(11+))复合辐射和Si~(11+)(n=3→n=2)跃迁发射的贡献,且它们辐射的最大强度距靶面130μm,对应的电子密度3×10~(20)cm~(-3)与Si~(11+)+1s~23d能级的粒子数相对丰度比36;实验中还观察到Si~(11+)(1s~23d-1s~22p)跃迁发射存在着明显的自吸收现象。     

Progress in the applicability of plasma X-ray lasers

Proposed as satellite-based weapons during the 1980s, X-ray lasing was for a long time only achieved with enormous amounts of pump energy in either nuclear explosions or at kilojoule-class laser installations. During the last few years a tremendous development was achieved, most visible in the realisation of the FEL lasers at DESY and SLAC. As important for a wider applicability is the enormous reduction in pump energy for laser pumped plasma X-ray lasers, which now brings such devices into the range of applications for diagnostics and spectroscopy even in smaller laboratories. Main developments were the transient excitation scheme and the optimized pumping concepts. This paper concentrates on developments at the GSI Helmholtzcenter at Darmstadt aiming towards reliable X-ray laser sources in the range from 50 to several 100 eV. The main driving forces for the laser development at GSI are the possible application for the spectroscopy of Li-like ions in the storage ring ESR and the future storage ring NESR at FAIR, and the interest in novel plasma diagnostics.     

复合X射线激光空间特性的研究

本文研究了类锂硅离子和类钠铜离子两种复合X射线激光的增益空间分布,结果表明复合X射线激光的增益出现在离靶面一定距离的中等等离子体电子密度区,而近靶面高密度区存在自吸收现象.     

Sc^18＋和Ti^19＋的辐射跃迁几率

计算表明,Sc~(18+)和Ti~(19+)的5f—3d和5d—3p跃迁波长处于水窗当中.进而,详尽地计算了这两个元素类锂离子的精细能级(n≤12,l≤5)及它们间的辐射跃迁几率.     

类锂硅离子软X射线激光的空间特性

本文报道类锂硅离子软X射线激光的空间分布特性,研究表明软X射线激光的最佳增益在离靶面约300μm的中等等离子体密度区,而临近靶面的高密度区增益则较小.     

类锂硅软X射线激光模拟

对１１６ｐｓ，功率密度为５．４×１０（１２）Ｗ／ｃｍ２的激光脉冲和硅平板靶的相互作用进行了数值模拟，得到了类锂硅离子４ｆ粒子波居数和４ｆ－３ｄ跃迁增益系数的时空变化，并与实验结果进行了比较。     

气体靶激光等离子体软X-射线源实验研究

介绍了一种无碎屑、高亮度、高工作频率的气体靶激光等离子体软X 射线源。其喷气阀门由压电陶瓷驱动 ,工作频率可达到 40 0Hz。与金属靶激光等离子体软X 射线源相比 ,此光源无碎屑。与喷嘴由电磁阀控制的气体靶激光等离子体软X 射线源相比 ,它有较高的工作频率。一工作在模拟模式的通道电子倍增器被用于探测来自光源的软X 射线辐射 ,其输出信号经过一电荷灵敏前置放大器进一步放大变成电压脉冲信号 ,脉冲幅度与输入电荷灵敏前置放大器的电量成正比。实验测得CO2 ,Xe和Kr在 8～ 2 2nm软X 射线投影光刻常用波段的光谱辐射特性。CO2 光谱包括类锂和类铍离子跃迁形成的线谱 ,Xe光谱是多电荷氙离子 4d 5f,4d 4f,4d 6p和 4d 5p跃迁所形成的光谱。Kr气体靶光谱包括类铜离子、类镍离子、类钴离子和类铁离子跃迁形成的线谱和连续谱。     

辐射输运实验中的Al等离子体发射光谱研究

SGII装置上用八路激光注入金腔产生高温辐射源,然后利用该辐射源来加热输运腔中的掺Al泡沫样品.从测量得到的Al类氦离子发射光谱可以观察到a—d,qr伴线的强度明显高于jkl伴线的强度,由此可以确定出光子激发和电离过程对输运腔中等离子体的形成不可忽略.除此之外,还观察到较强的互组合线发射,这表明存在一个低密度区域.最后考虑到实验测量得到的Al类氦离子发射光谱是时间、空间积分,利用两个状态等离子体的发射光谱合成再现了实验光谱. 关键词： 发射光谱 辐射加热 光谱诊断     

Soft X-ray amplification by Li-like Al10+ and Si11+ ions in recombining plasmas

Experimental studies of soft X-ray lasers were carried out on the six-beam laser facility and the LF 12 laser facility of SIOM. Using a home-made one-dimensional spatially resolved grazing incidence grating spectrograph, XUV amplification has been observed in Li-like aluminum and silicon ions, by irradiation of slab targets with a line-focused laser. Based on time-integrated measurement, gain coefficients are 3.1 cm^–1 for the 105.7 Å 5f–3d transition in Li-like Al ions, and 1.5 cm^–1 and 1.4 cm^–1 for the 88.9 Å 5f–3d and the 87.3 Å 5d–3p transitions in Li-like Si ions, respectively. The maximum gain × length products (GL) are about 2.5.     

Formation of conical microstructures upon laser evaporation of solids

The formation and development of the large-scale periodic structures on a single crystal Si surface are studied upon its evaporation by pulsed radiation of a copper vapor laser (wavelength of 510.6 nm, pulse duration of 20 ns). The development of structures occurs at a high number of laser shots (∼10⁴) at laser fluence of 1–2 J/cm² below optical breakdown in a wide pressure range of surrounding atmosphere from 1 to 10⁵ Pa. The structures are cones with angles of 25, which grow towards the laser beam and protrude above the initial surface for 20–30 μm. It is suggested that the spatial period of the structures (10–20 μm) is determined by the capillary waves period on the molten surface. The X-ray diffractometry reveals that the modified area of the Si substrate has a polycrystalline structure and consists of Si nanoparticles with a size of 40–70 nm, depending on the pressure of surrounding gas. Similar structures are also observed on Ge and Ti. Received: 12 February 2000 / Accepted: 28 March 2000 / Published online: 20 June 2001     

超相对论强度激光与薄膜靶作用中0.4 nm以下X射线阿秒脉冲的产生

用一维粒子模拟程序对功率密度在10²² W/cm²以上的超强激光驱动薄膜靶产生的相对论电子层及其经过汤姆孙散射产生的阿秒X射线进行了研究. 结果表明, 在超相对论强度范围下增大驱动激光强度, 相应减小等离子体密度及厚度可使电子层获得更高纵向动量, 使汤姆孙散射光明显向更短波长移动. 优化相关参数得到了波长为 1.168 nm的阿秒脉冲. 经过对倍频探测光方案与驱动光以及薄膜靶参数进行综合考虑和优化, 得到的X射线相干辐射波长有效减小到0.4 nm以下, 产生的光子能量达到2 keV以上. 关键词： 超相对论强度激光 阿秒X射线 相对论电子层 汤姆孙后向散射     

Capillary discharge tabletop soft X-ray lasers reach new wavelengths and applications

For many years, researchers have envisioned the development of compact high repetition rate tabletop soft X-ray lasers that could be routinely used in application in numerous disciplines. With demonstrated average powers of several mW and mJ-level pulse energy at 46.9 nm, capillary discharge-pumped lasers are the first compact lasers to reach this goal. In this paper we summarize the development status of high repetition rate tabletop soft X-ray lasers based on capillary discharge excitation, and give examples of their successful use in several applications. Results of the use of a capillary discharge pumped 46.9 nm laser in dense plasma interferometry, soft X-ray reflectometry for the determination of optical constants, and laser ablation are described. The observation of lasing at 53 nm line in Ne-like Cl with output pulse energy up to 10 μJ is also reported.     

120TW/30fs激光产生的Al等离子体X射线发射谱分析

在SILEX激光装置上利用超强超短激光(120TW/30fs)与Al靶相互作用产生热稠密等离子体.采用类氢共振线与类氦共振线线强比诊断得到电子温度在480～670eV之间,采用类锂jkl伴线与类氦共振线强度比得到电子温度在430～610eV之间,两种诊断方法得到的结果基本一致.用类氦互组合线与类氦共振线强度比方法获得电...