Generation and characterization of a bright X-ray source using picosecond laser

High-resolution soft X-ray spectra of H-like and He-like ions were produced from laser irradiated silicon and aluminum targets. Plasma size was about 100 μm. X-ray spectra were analyzed to determine plasma parameters. We compared the line shape of resonance transitions and their intensity ratios to corresponding dielectronic satellites and the intensities of the inter combination lines of He-like ions, with the results of model calculations. Such comparison gave average values of the electron density N _e=(1?1.9)×10²¹ cm^?3 and the electron temperature T _e=460–560 eV for Si plasmas and about 560 eV for Al plasmas produced by the first and the second laser harmonics. According to our estimations, more than 10¹² photons were produced within the resonance line spectral width and in the solid angle 2π steredian during the total decay period.     

A low debris laser plasma soft X-ray source

Low debris laser plasma soft X-ray source is of great importance to micro-lithography and microscopy. In this paper, a 1.06 μm YAG laser with 2 J energy, 10 ns duration is employed to irradiate a CO₂ cryogenic target. Soft X-ray spectra from the CO₂ cryogenic target are obtained. Experimental results of debris measurement from both CO₂ cryogenic and Cu targets demonstrate that the light source based on the CO₂ cryogenic target shows great improvement over conventional metal targets in debris reduction.     

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。     

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。     

Plasma satellites of X-ray lines of ions in a picosecond laser plasma

We present the results of our measurements of the spectra for multicharged ions in a plasma produced by moderately intense (about 10¹⁷Wcm^?2) picosecond laser pulses. They suggest the existence of intense plasma oscillations with a frequency appreciably lower than the frequency of the laser radiation. The observed spectrum for the plasma satellites of the Lyman Ly_α doublet of the hydrogenic F IX ion in a dense plasma was modeled theoretically. The resulting doublet profile was shown to have a complex structure that depends non-trivially both on the plasma density and on the frequency and amplitude of the plasma oscillations. The positions of the satellites and their separations allowed them to be associated with intense electrostatic oscillations with an amplitude of (4–6)×10⁸Vcm^?1 and a frequency near (0.7–1)×10¹⁵s^?1. Assuming the oscillation frequency to be determined by the strength of the magnetic field B generated in the plasma, we obtained an estimate of B that is in reasonable agreement with other measurements and estimates of this quantity. Our theoretical analysis allowed explanation of the emission spectra observed when flat fluoroplastic targets were heated by intense picosecond laser pulses.     

均匀线状激光等离子体X光单色源和软X光胶片响应特性的标定

利用均匀线聚焦激光产生的等离子体和软X针孔透射光栅谱仪获得了均匀的线状软X光单色光源.在这一光源基础上,利用加阶梯膜的新方法首次标定了国产无保护层5F软X光胶片在软X光波段的响应特性.     

A picosecond near-infrared laser source based on a self-seeded optical parametric generator

We report on the design and development of a new type of near-IR laser source. The source comprises of an optical parametric generator (OPG) and a second harmonic generator (SHG) pumped by an 80-MHz, 1064-nm, 7-ps Nd:YVO₄ laser. The OPG is self-seeded with a fraction of its own signal output, which significantly enhances its conversion efficiency. The SHG doubles the frequency of OPG signal to produce a coherent output. The final output beam has a tunable wavelength near 800 nm, an average power of over 1 W, and a pulse duration around 5 ps. The M²-factor of the output beam can reach 1.1 after spatial filtering. With the new laser source, we have successfully demonstrated coherent anti-Stokes Raman scattering microscopy on 1 μm polystyrene beads, which shows that it has the potential to be a substitute for a picosecond optical parametric oscillator in certain microscopy or spectroscopy applications.     

Investigations on laser plasma soft X-ray sources generated with low energy laser systems

Spectra of laser-induced plasmas at low laser energies and intensities (around 100 mJ and 10¹⁰ W cm^–2 respectively) have been recorded in the spectral range of 20 to 100 nm for different target materials, laser intensities at the target and laser wavelengths. For heavy target materials, a broadband spectrum with a spectral maximum typically around 30 nm is obtained. This broadband radiation source is well suited for photoionization processes and the generation of short wavelength inner-shell photoionization lasers. For the cadmium-photoionization laser, the influence of different soft X-ray spectra on the laser energy has been investigated. The potential of laser plasma soft X-ray sources for scientific and technical applications is briefly reviewed.Dedicated to Prof. Dr. Herbert Welling on the occasion of his 60th birthday     

Space-resolved soft X-ray emission from laser produced lithium plasma

Space-resolved emission spectroscopy was used to study the evolution of 13.5 nm line intensity and electron temperature of the plasma generated by laser ablation of lithium target. Two emitting regions were observed, their intensities depending on laser fluency. Plasma image is discussed in the frame of a Gaussian model of particle expansion.     

激光等离子体软X光源8—20nm光谱辐射研究

研制了了一种脉冲重复频率为１０Ｈｚ的激光等离子软Ｘ射线源；傅波长０．５３μｍ和波长１．０６μｍ的激光脉冲，聚焦在不同的金属靶上，使之离子化。     

Design of capillary Z-pinch plasma for a soft X-ray laser

An analysis for designing capillary Z-pinch plasma as an alternative active medium of soft X-ray laser is presented. The validity of calculation results are verified by experiment. Namely, the specification of driving current as well as the predicted pinch time is in good agreement with the experimental results. This study also reveals the possibility of reducing the main charging voltage without degrading the performance of the X-ray laser.     

Scope of plasma focus with argon as a soft X-ray source

The X-radiation emission from a low energy plasma focus with argon as a filling gas is investigated. Specifically, the attention is paid to determine the system efficiency for argon K-lines and Cu-K/sub /spl alpha// line emission at different filling pressures, and identify the radiation emission region. The highest argon line emission found at 1.5 mbar is about 30 mJ and the corresponding efficiency is 0.0015%. The same pressure is suitable for high Cu-K/sub /spl alpha// emission, which is about 70 mJ in 4/spl pi/ geometry and the system efficiency is 0.003%. The bulk of X-radiation is emitted from the region close to the anode tip, whereas some radiation emission takes place from the formed hot spots along the focus axis. These radiations are found suitable for backlighting in Al (1-1.56 keV) and Ti (2.9-4.96 keV) energy transmission bands.     

激光-近临界等离子体高能高亮度X射线的产生

基于激光驱动超热电子产生的高品质X射线源是高能量密度实验中有效的诊断技术手段,对辐射源亮度、穿透性和时空分辨率等特性具有极高的要求。结合粒子模拟和蒙特卡罗模拟研究,首先利用近临界密度等离子体实现了激光自聚焦通道中的大电量高能电子加速,通过直接加速机制产生了电量超过600 nC、有效温度可达15 MeV的高能电子;以此为基础提高电子-光子能量转换率,有效优化了光子能量和产额,并通过一定的转换靶参数优化方案产生了微焦点(FWHM小于200 m)、高能、高亮度X射线,为高空间分辨(小于200 m)成像诊断提供了很好的途径,有望早日实现激光等离子体轫致辐射单脉冲瞬态照相的实际应用。     

软X射线激光探针诊断高$lt;i$gt;Z$lt;/i$gt;材料等离子体

激光辐照靶产生的等离子体电子密度的诊断对于惯性约束聚变、高能量密度物理等相关领域的研究具有重要意义,特别是高Z材料等离子体临界面附近的电子密度分布信息的测量. 利用软X射线激光作为探针是诊断等离子体电子密度分布的一种重要方法,但在诊断激光辐照高Z材料产生的等离子体研究中,遇到了高Z材料等离子体自发辐射过大的问题,难以开展. 为此,针对软X射线激光的特点,发展了多种具体的实验技术. 通过综合利用这些技术,大大的抑制了待测等离子体自发辐射对信号的影响,使得软X射线激光探针诊断高Z材料等离子体成为可能. 作为典型例子,实验诊断了激光辐照金平面靶的等离子体,获得了清晰的实验图像,表明相关的技术是有效和可行的. 关键词： 等离子体诊断 激光探针技术 软X射线激光 Z材料等离子体')" href="#">高Z材料等离子体     

激光-近临界等离子体高能高亮度X射线的产生

基于激光驱动超热电子产生的高品质X射线源是高能量密度实验中有效的诊断技术手段,对辐射源亮度、穿透性和时空分辨率等特性具有极高的要求。结合粒子模拟和蒙特卡罗模拟研究,首先利用近临界密度等离子体实现了激光自聚焦通道中的大电量高能电子加速,通过直接加速机制产生了电量超过600 nC、有效温度可达15 MeV的高能电子;以此为基础提高电子-光子能量转换率,有效优化了光子能量和产额,并通过一定的转换靶参数优化方案产生了微焦点(FWHM小于200 m)、高能、高亮度X射线,为高空间分辨(小于200 m)成像诊断提供了很好的途径,有望早日实现激光等离子体轫致辐射单脉冲瞬态照相的实际应用。     

X-ray source based on a compact electron linear accelerator with a thin anode

An experiment confirming the possibility of extracting a narrow energy band from a wide spectrum produced by a compact electron linear accelerator with a thin transmission anode is described. A flat crystal of pyrolytic graphite was used as a monochromator.     

皮秒脉冲激光产生的X射线源能谱精密诊断

针对皮秒脉冲激光产生的X射线能谱精密诊断需求,提出了一种晶体谱仪,该谱仪使用曲率为200 mm的透射式石英弯晶作为色散元件,测谱范围可覆盖8～60 keV。使用该谱仪在星光III和神光II升级装置进行了应用,成功获得了铜、钼、银等元素的特征线能谱,以及金的L壳层特征线,测量获得的能谱信噪比较高,显示了谱仪在测量皮秒激光产生的X射线能谱上的良好性能。     

软X射线激光偏折法测量激光等离子体电子密度分布

利用脉宽约为50ps的类镍银139nm软X射线激光作为探针,探测由脉宽80ps的驱动激光打C8H8靶产生的等离子体在1ns后的电子密度分布信息,获得了清晰的莫尔条纹图像.对结果的处理,给出了峰值电子密度为11×1021cm-3,并对在靶面附近莫尔条纹的消失现象作了初步解释 关键词： 软X射线激光探针 莫尔条纹 等离子体电子密度     

基于自相似模型的二维X射线激光等离子体流体力学

从自相似方法出发,建立了简化的二维X射线激光等离子体流体动力学模型. 利用该模型研究了平板靶X射线激光的二维流体力学行为. 研究表明,当激光作用结束后,经过一段时间的演化电子密度和温度沿线聚焦方向逐渐达到平衡,该结果对X射线激光的优化设计具有重要意义. 关键词： X射线激光 二维流体力学计算 自相似方法