高温铝等离子体X光发射谱实验

 在神光-Ⅱ高功率激光装置上,以束匀滑的第九路钕玻璃二倍频激光均匀辐照薄层铝埋点靶,通过激光烧蚀作用产生较均匀的铝高温等离子体,用平面晶体谱仪在靶面前向和切向同时测量了X光发射谱信号,并将前向发射谱进行了定量化还原处理。利用辐射流体力学程序MULTI-1D首先对等离子体状态进行了模拟计算,然后采用基于碰撞辐射模型的光谱程序对该状态下的光谱开展了计算,并将实验测量光谱与理论计算光谱进行了比较和分析,符合得较好。     

金激光等离子体的空间分辨X射线发射谱及其应用

在星光II激光装置上,采用PET平面晶体谱仪与宽20μm的狭缝构成一维空间分辨光谱测量系统,对金平面靶激光等离子体进行观测,获得了沿靶面法向一维空间分辨的金M带发射谱。在实验谱中观察到了Au元素类Ni离子的电四极跃迁线3p63d10(1S0) 3p53d104d(3/2,5/2)J=1。利用电四极跃迁线对电子密度的敏感特性,开展了金激光等离子体电子密度诊断的尝试,确定出利用该谱线进行电子密度诊断的有效范围大致在1019～4.5×1021cm-3之间。     

Analysis of X-ray spectra emitted from a laser-produced lead plasma

X-ray spectra emitted by a laser produced plasma are analyzed using calculated X-ray energies for Co-, Ni-, Cu-, Zn-, Ga-, Ge-, As-, Se-, Br-, Kr-, Rb-, Sr-, Y-, and Zr-like lead ions. The charge state distribution in the plasma is studied and a functional dependence of this distribution as a function of the ionic charge, atomic number, free electron density and temperature in the plasma is proposed.     

Retrieval of currents of multiply charged ions emitted from laser-produced carbon plasma

The emission of ions from laser-produced carbon plasmas is investigated by a deconvolution of ion collector signals. The deconvolution is based on the use of Kelly and Dreyfus function expressing the time-resolved ion current to recover hidden peaks in an ion collector signal. The parameters of recovered C ^q+ (1?≤?q?≤?6) currents make possible the quantification of properties of laser-produced plasmas. The drift and peak velocities of C ^q+ ions, the abundance of ions and the plasma temperature are presented in the dependence on focused laser beam energy. The carbon plasma was generated employing either single 9-ns pulses of second harmonics (532 nm) of Nd:YAG laser or pulses repeated at a stable repetition rate of 30 Hz.     

Suppression of fast-ions from a laser-produced plasma

Fast-ion emission occurs when a target is irradiated with single 25 psec pulses from a Nd: YAG/glass laser but is suppressed when the same target is irradiated with a mode-locked pulse train at the same intensity. Possible explanations for this effect are given.     

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     

Observations of light back-scattered from a laser-produced plasma

The back scattered light from a laser-produced plasma has been investigated. The laser consisted of a ruby oscillator and one amplifier producing a 10-nsec pulse of 10 joules. Observations of a Doppler-shifted component and of satellite lines are reported.     

Imaging using hard X-rays from a laser-produced plasma

Imaging of technical and biological objects using hard X-rays from a laser-produced plasma source is demonstrated. Magnification radiography and single-shot imaging of biological samples are feasible with the source, which utilised focused radiation from a short-pulse terawatt laser. Differential imaging with element specificity and a new projection geometry for X-ray radiography are proposed.     

Magnetic-field confinement of a laser-produced plasma

Summary Ruby-laser pulses have been focused onto planar targets of beryllium in a magnetic field,B=17 kG. The field was oriented parallel to the direction of the incoming laser beam and perpendicular to the target surface. It was balancing the kinetic pressure of the plasma at a few millimeters from the target. Spectroscopic observations, both time integrated and time resolved, have shown the magnetic-confinement effect. In particular, a reduction of the transverse plasma-plume size and a density increase and slower expansion, in the presence of the magnetic field, have been observed. In the introduction, a short review of the most recent papers on the subject is reported.

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Riassunto Gli impulsi luminosi di un laser a rubino sono stati focalizzati su bersagli piani di berillio in un campo magnetico di 17 kG. Il campo era orientato parallelamente alla direzione del fascio laser incidente e perpendicolarmente alla superficie del bersaglio ed era tale da bilanciare la pressione cinetica del plasma a qualche millimetro dal bersaglio. Osservazioni spettroscopiche, sia integrate che risolte nel tempo, hanno mostrato l’effetto di confinamento magnetico. In particolare, sono stati rilevati, in presenza del campo magnetico, una riduzione delle dimensioni trasversali del pennacchio di plasma ed un incremento della densità con rallentamento dell’espansione del plasma. Nell’introduzione è riportata una breve rassegna dei lavori piú recenti sullo stesso argomento.

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Резюме Импульсы рубинового лазера фолусируются на плоские мишени бериллия в мапитном поле,B=17 кГс. Магнитное поле ориентировано параллельно направлению падающего лазерного лучка и перпендикулярно поверхности мишени. Кинетическое давление плазмы уравновешивается в нескольких миллиметрах от мишени. Спектроскопические наблюдения указывют на зффект мапнитнопо В частности, наблюдаются умеиьшение поперечнопо поперечнопо размера плазмы, увеличение плотности и расшение расширения в присутствии мапнитнопо поля. Во введении предлапается краткий обзор недавних работ на эту тему.

     

天体等离子体中铝发射谱线的研究

结合天体等离子体中铝发射谱和某些能级寿命的测量,对束箔光谱技术可为天体物理学研究提供重要信息和重要性进行了简述     

Ultimate efficiency of extreme ultraviolet radiation from a laser-produced plasma

An analytical formula for maximizing radiation efficiency from a laser-produced plasma is derived. The maximum efficiency is achieved when the plasma expansion distance during laser heating is equal to the laser absorption length. The dependence of the radiation efficiency on the plasma density is confirmed by experiments using a particle-cluster target. By creating a relatively uniform density plasma with a 300 microm diameter by dispersing SnO(2) particles coated on a Si wafer, the conversion efficiency at 14 nm, as high as 4 times as that for a Sn plate target, is achieved.     

Surface modification of platinum by laser-produced X-rays

Laser-induced plasma is used as an X-ray source for the growth of hillocks like nanostructures on platinum surface. To generate X-rays, plasma is produced by Nd:YAG laser, which is operated at second harmonics (λ?=?532?nm, E?=?400?mJ). Analytical grade 5?N pure Al, Cu and W are used as laser targets for X-rays production. X-rays produced from Al, Cu and W plasmas are used to irradiate three analytical grade (5?N pure) platinum substrates, respectively, under the vacuum ～10^?4 torr. XRD analysis shows considerable structural changes in the exposed platinum. The decrement in reflection intensities, increment in dislocation line density, change in d-spacing and disturbance in the periodicity of planes evidently prove these structural changes. Atomic force microscope AFM topographic analysis of the platinum exposed to X-rays emitted from Al, Cu and W targets showed that nanometer-size hillocks are produced on the platinum surface irrespective of the source. It has also been observed that due to these hillocks, the roughness of the surface has increased. Conductivity of hillocks produced from X-rays produced by Al, Cu and W targets is compared and it is shown that the hillocks produced by Al target X-rays have better conductivity compared to the hillocks produced by X-rays from Cu and W targets.     

Optimization of EUV radiation yield from laser-produced plasma

We optimize the conversion of laser energy into extreme ultraviolet (EUV) radiation by tailoring the laser parameters for a laser-produced plasma generated from 20 μm diameter water droplets. It is shown that mass-limited targets require careful adaption of laser-pulse energy and laser-pulse duration separately, rather than laser intensity, which seems to be adequate for bulk targets. The optimal pulse duration scales with the droplet radius, and the optimal pulse energy with the droplet volume. With optimized parameters, we obtain a conversion efficiency of 0.23% in 4π and 2.5% bandwidth for 13 nm radiation, the future EUV lithography light. Received: 16 July 2001 / Revised version: 25 September 2001 / Published online: 7 November 2001     

Relativistic second-harmonic generation in a laser-produced plasma

Summary In this paper the relativistic second-harmonic generation of a high-power laser radiation in a laser-produced plasma has been studied theoretically in the presence of a self-generated magnetic field. The relativistic Vlasov equation has been employed for the nonlinear response of the electrons in the hot magnetized plasma. It is observed that the power conversion efficiency of the generated second harmonic wave is much higher for relativistic calculations than that for nonrelativistic calculations. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Mechanisms for three-halves harmonic emission from laser-produced plasma

Three halves harmonic emission from thin foil targets irradiated with high power ( > 10¹⁶ W cm^-2) Nd laser pulses is reported. Spectral differences between forward and backscattered 3ω₀/2 emission are seen, explained by plasmon/photon and three plasmon recombination.     

Time-resolved studies of deuteron beams emitted from a plasma focus

Fast (0.3—2.5 MeV) deuterons are registered with scintillator-photomultiplier detectors placed behind a Thomson analyzer. Time delays of deuteron signals (minimum FWHM ? 8 ns) in relation to X-ray signals are consistent with times of flight and show that the ions are emitted with a jitter smaller than 5 ns. Longer multi-spike ion pulses sometimes observed are interpreted.     

Observations of MeV ions emitted from a laser produced plasma

Fast-ion emission from tungsten plasmas has been studied with neodymium laser intensities from 5x10¹² to 2x10¹⁵ W/cm². Ion energies into the MeV region have been observed. The variation of ion energy (E_I) with laser intensity (I) was found to be of the form E_I∞I^0.65.