X-ray spectroscopy from variable,Z laser-produced plasmas

We have investigated the sensitivity of X-ray line intensities as a laser-plasma diagnostic by seeding Si in CH and PbO plasmas. The Si K X-ray spectrum is measured using both time-integrating and time-resolving spectrographs to investigate the effect of time averaging on the line intensities. The measured intensities are compared with theoretical estimates for an isothermal, isodensity plasma. Si line intensities vary with the Z of the plasma, as expected from simple scaling models, indicating the Si lines can be a good plasma diagnostic. The line intensities do not predict a unique temperature and density, but, instead, the inferred temperature and density vary, depending on the line ratio used. These variations are attributed to large spatial gradients of temperature and density in the plasmas. Problems in interpretation are discussed, as well as possible directions for future experiments.     

Broadband time-resolved elliptical crystal spectrometer for X-ray spectroscopic measurements in laser-produced plasmas

The X-ray spectrometer used in high-energy-density plasma experiments generally requires both broad X-ray energy coverage and high temporal, spatial, and spectral resolutions for overcoming the difficulties imposed by the X-ray background, debris, and mechanical shocks. By using an elliptical crystal together with a streak camera, we resolve this issue at the SG-II laser facility. The carefully designed elliptical crystal has a broad spectral coverage with high resolution, strong rejection of the diffuse and/or fluorescent background radiation, and negligible source broadening for extended sources.The spectra that are Bragg reflected(23?< θ < 38?) from the crystal are focused onto a streak camera slit 18 mm long and about 80 μm wide, to obtain a time-resolved spectrum. With experimental measurements, we demonstrate that the quartz(1011) elliptical analyzer at the SG-II laser facility has a single-shot spectral range of(4.64–6.45) keV, a typical spectral resolution of E/?E = 560, and an enhanced focusing power in the spectral dimension. For titanium(Ti) data, the lines of interest show a distribution as a function of time and the temporal variations of the He-α and Li-like Ti satellite lines and their spatial profiles show intensity peak red shifts. The spectrometer sensitivity is illustrated with a temporal resolution of better than 25 ps, which satisfies the near-term requirements of high-energy-density physics experiments.     

X-ray spectrometry of laser-produced aluminum plasmas

X-ray lines and continuum emission from a laser-produced aluminum plasma have been studied. The electron temperature variations during the laser pulse (30 ns) were deduced from time-dependent measurements of intensities of resonance lines (2.5 ns time-resolution). Comparison is made with electron temperature values deduced from ion emission measurements.     

Analysis of X-ray spectra emitted from laser-produced plasmas of uranium

In this paper, we used the multiconfiguration Dirac-Fock method to generate theoretical X-ray spectra for Co-, Ni-, Cu-, Zn-, Ga-, Ge-, As-, Se-, Br-, Kr-, and Rb-like uranium ions. Using the distribution of these ions in a laser-produced plasma, for different plasma temperatures, we generate theoretical spectra which are compared to experimental data. Electronic supplementary material  Supplementary Online Material The transition probabilities and energies calculated in this work are available in electronic form at http://www.epj.org     

激光等离子体软X射线辐射能谱时间分辨测量研究

利用(国内最近研制成功的)带聚酰亚胺膜底衬的金透射光栅与软X射线条纹相机相配合,(在LF11~#激光装置上)使用波长为0.53μm的激光打靶,测量了平面Au靶软X射线时间分辨能谱。测量结果观察到了金等离子体的O带辐射强度随时间增加的现象。文章计算了光栅的衍射效率,并讨论了影响测量谱的几个关键因素。     

Spatial-temporal measurements of magnetic fields in laser-produced plasmas

The results of an investigation of the electromagnetic wave polarization, probing high-temperature laser plasma, as well as spatial-temporal structure of the magnetic fields, electron density, current density, and electron drift velocity are presented. To create the plasma, plane massive Al targets were irradiated with the second harmonic of a phoenix Nd laser at intensities up to 5·10¹⁴ W/cm². It was shown that the magnetooptical Faraday effect is the main mechanism responsible for the changing polarization of the probing wave. Magnetic fields up to 0.4 MG with electron densities ∼10²⁰ cm⁻³ were measured. Analysis of the magnetic field spatial distribution showed that the current density achieved the value ∼90 MA/cm² on the laser axis. The radial structure of the magnetic field testified to the availability of the reversed current in the laser plasma. The spatial and temporal resolutions in these experiments were equaled to ∼5 μsec and ∼50 psec, respectively. Translated from Preprint No. 35 of the Lebedev Physics Institute, Moscow, 1993.     

X-ray gain in laser-produced carbon plasmas using double-layer targets

We investigate from a theoretical point of view the basic possibilities for the effect of ionizing radiation on the X-ray gain in recombining laser-produced plasmas, in particular with regard to recently performed experiments in which targets consisting of two different-material layers (double-layer targets) were used. We discuss an increase of the gain for the 3 2 transition in hydrogenic ions which is due to photoionization causing, mainly, a decrease of the Lyman- reabsorption and an increase of the population of higher levels. In our numerical simulations we consider single-material and double-layer targets, concentrating particularly on carbon and titanium. We obtain and discuss the time behaviour of the X-ray emission from the laser-produced plasma with regard to its application as pump radiation.     

Ion and X-ray techniques used for study of laser-produced plasmas

This review article describes apparatus for ion and X-ray diagnostics, which were used in experimental studies of laser-produced plasmas performed by the IPPLM's team in collaboration with other researchers at IPPLM and PALS Research Centre in Prague (the Czech Republic). The investigations of expanding laser-produced plasma properties in dependence on laser beam parameters were done by means of ion diagnostics devices: ion collectors (ICs), cylindrical ion energy analyzer (IEA) and the mass spectrograph of the Thomson type. At IPPLM, different types of detectors have been developed for measurement of X-ray emission. Properties of laser-produced beams of ions and X-ray radiation were analysed in the cooperative experiments performed with the use of a high-energy iodine laser PALS at the PALS Research Centre ASCR in the Czech Republic and the low-energy repetitive laser at IPPLM.     

Reflectance measurements on laser-produced plasmas at 0.26 μm

Total and specular reflection from planar Al-targets was measured with a frequency-quadrupled (λ = 0.26 μm) Nd-YAG laser. The intensity on target was 4 × 10¹³ W/cm² with pulse duration 20 ps. Total absorption for near normal incidence was 80%, very little dependence on intensity and pulse duration was found. By varying the polarization and angle of incidence (0°–80°) the characteristic behaviour of resonance absorption was observed.     

Elliptically-bent crystal spectrograph for X-ray diagnosis of laser-produced plasmas

In order to measure spatially and temporarily resolved laser-produced plasma X-ray spectra in 0.2 - 2nm region, a novel two-channel elliptically-bent crystal spectrograph has been developed. Dispersive elements are LiF, PET, Mica, and KAP crystals, which cover Bragg angles in the range of 30 - 67.5degrees. Eccentricity and focal distance of twin ellipses are 0.9586 and 1350 mm, respectively. Spatially resolved spectrum is photographically recorded with an X-ray film or X-CCD camera in one channel, and temporarily resolved one is photographically recorded with an X-ray streak camera in another channel,thus spatially and temporarily resolved spectra can be simultaneously obtained. Spectral images were acquired with X-CCD and PET in SHENGUANG-Ⅱ laser facility, and experimental results show that the spectral resolution of the spectrograph is about 0.002 nm.     

基于激光等离子体研究的高性能扫描晶体谱仪（英）

在激光等离子体研究中,电磁脉冲干扰对实验结果影响很大,为了减小这一影响,设计一款新的扫描晶体谱仪,整个机身设计成几乎全密闭的良导体。该晶体谱仪通过更换晶体和调整入射角可以获得较宽范围的测量窗口。在X光光谱为2.5~3.5 keV范围内的测量试验中,该扫描晶体谱仪的谱分辨能力为13（在2960 eV）,时间分辨率为10 ps。其谱分辨和时间分辨可以满足对激光等离子体的研究。     

基于激光等离子体研究的高性能扫描晶体谱仪（英）

在激光等离子体研究中,电磁脉冲干扰对实验结果影响很大,为了减小这一影响,设计一款新的扫描晶体谱仪,整个机身设计成几乎全密闭的良导体。该晶体谱仪通过更换晶体和调整入射角可以获得较宽范围的测量窗口。在X光光谱为2.5~3.5 keV范围内的测量试验中,该扫描晶体谱仪的谱分辨能力为13（在2960 eV）,时间分辨率为10 ps。其谱分辨和时间分辨可以满足对激光等离子体的研究。     

Evidence of suprathermal electron fluxes in laser-produced plasma from the polarization and anisotropy of X-ray bremsstrahlung emission

Polarization and angular distribution of suprathermal X-ray emission from plasma produced by picosecond ruby laser pulses have been measured. Polarization of 12 ± 3 percent and anisotropy of X-ray angular distribution evidence the existence of suprathermal electron fluxes in plasma. Their direction corresponds to resonance absorption mechanism.     

Dielectronic satellite spectra from dense laser-produced plasmas

The Lyman-α and adjacent dielectronic satellite lines have been observed in the spectra from laser-irradiated solid targets. In a carbon plasma from a planar target, the relative intensity of the $\text{2p}{}^2{}^3\text{P?1s2p}{}^3\text{P}$ satellite line of C(V) increases as a function of electron density in the range 8 × 10¹⁹ to 2 × 10²⁰ cm^?3. As analysis of a series of imploded microballoon experiments indicates that the $\text{2p}{}^2{}^3\text{P?1s2p}{}^3\text{P}$ and $\text{2s2p}{}^3\text{P?1s2s}{}^3\text{S}$ satellite radiation of Si(XIII) increases for electron densities 1 × 10²²?2 × 10²³ cm^?3. The satellite intensity distributions have been numerically simulated using a rate equation model. It is shown that the carbon and silicon satellite data may be interpreted in a consistent manner, and the extension to higher atomic numbers Z and higher electron densities is considered.     

Au等离子体M带5f-3d跃迁透射谱的理论模拟

基于细致组态(DCA)方法和跃迁系列群 (UTA) 模型,采用全相对论处理并结合量子亏损理论,计算了金Au激光等离子体的M带5f-3d跃迁的透射谱, 给出了金等离子体在不同电子温度和电子密度的时空电离态特性,平均电离度,离子丰度和离子内各能级的布居数,并模拟出Au等离子体的M 带5f-3d跃迁的细致谱线,其计算结果可对激光等离子体透射谱的电子温度和电子密度进行精密诊断.