共查询到20条相似文献,搜索用时 15 毫秒
1.
Cavalieri AL Fritz DM Lee SH Bucksbaum PH Reis DA Rudati J Mills DM Fuoss PH Stephenson GB Kao CC Siddons DP Lowney DP Macphee AG Weinstein D Falcone RW Pahl R Als-Nielsen J Blome C Düsterer S Ischebeck R Schlarb H Schulte-Schrepping H Tschentscher T Schneider J Hignette O Sette F Sokolowski-Tinten K Chapman HN Lee RW Hansen TN Synnergren O Larsson J Techert S Sheppard J Wark JS Bergh M Caleman C Huldt G van der Spoel D Timneanu N Hajdu J Akre RA Bong E Emma P Krejcik P Arthur J Brennan S 《Physical review letters》2005,94(11):114801
Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms. 相似文献
2.
X rays from optical-field ionized plasmas at low density 总被引:1,自引:0,他引:1
We present results of an experiment in which x rays from an optical-field ionized plasma are generated under well-controlled conditions in a low-pressure gas cell. In this way high-density effects such as electron heating, collisional ionization, and ionization defocusing are avoided. Using N(2) as the medium, we show that many features of the soft-x-ray emission follow theoretical predictions. In particular, higher x-ray intensity is observed on most lines for circularly than for linearly polarized light. However, several Li-like lines show anomalously strong emission for linear polarization. Mechanisms that may be responsible for this effect are discussed. 相似文献
3.
4.
J.F. Seely R.H. Dixon R.C. Elton J.G. Lunney 《Journal of Quantitative Spectroscopy & Radiative Transfer》1982,27(3):297-306
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 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 and 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. 相似文献
5.
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. 相似文献
6.
R.L. Kauffman R.W. Lee D.L. Matthews J.D. Kilkenny 《Journal of Quantitative Spectroscopy & Radiative Transfer》1984,32(4):335-342
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. 相似文献
7.
B. Luther-Davies 《Optics Communications》1977,23(1):98-104
Fast-ion and suprathermal electron energies have been measured from plasmas generated by 25 ps duration neodymium laser pulses focussed onto solid targets. The relationship between the fast-ion energy and the energy of the suprathermal electrons in the plasma has been demonstrated and these energies have been found to increase in proportion to I0.35±0.05 for targets of aluminum and copper, with I the laser intensity. 相似文献
8.
A general criterion is proposed predicting the onset of chaotic behavior for parametric processes in a laser-produced plasma. The conditions when the transition to the stochastic regime occur are determined for various parametric instabilities excited when a high intensity laser interacts with a plasma. The complicated temporal structure observed in 3/20, 20, 10, and fast electron emission in experiments using high-intensity (I1015–17 W/cm2), short (
L
40–200 psec) Nd laser pulses is attributed to the reflection seeded SBS instability being driven into this regime.Lebedev Physics Institute, Leninsky Prospect 53, Moscow 117924 Russia. 相似文献
9.
We describe a steady state density and temperature dependent atomic physics package TRIP (4) which we have incorporated into a 1-D lagrangian computer code MEDUSA. Using this modified version of the code we evaluate the degree of ionization and study the effect of atomic processes in laser-compression simulations of gas filled micro-balloons. 相似文献
10.
Microplasmas produced from 15 μm methanol droplets irradiated by 100 fs laser pulses in the intensity range 1014–1016 W cm?2 are investigated via measurements of the hot electron temperature and x-ray yields under different conditions of intensity, polarization state, and plasma scale-length. The scale length of the drop-let plasma is increased with an intentional prepulse that is 10 ns ahead of the main pulse. Hot electron temperatures up to 48 keV have been measured at intensities of 2.5 × 1015W cm?2 and the scaling of temperature as a function of intensity is determined for a long scale-length droplet plasma. The polarization and ellipticity dependence of the hard x-ray yield from the microdroplet plasmas are used to probe the shape of the droplet after irradiation by a prepulse. 相似文献
11.
《Optics Communications》1987,61(3):199-202
In line-focused laser-produced plasma experiments on planar and cylindrical targets, we have observed the line-focused laser beam breakup into filaments as well as small-scale plasma jet-like structures. These phenomena might become obstacles in achieving optimum X-ray lasing in the type of experiments using line-focused laser-produced plasmas as a gain medium. 相似文献
12.
The relative intensities of the blue- and red-shifted satellites of three-halves harmonic spectra backscattered from plasmas produced by irradiation of targets with a high power Nd laser pulse have been measured. These have been used to estimate the plasma density scalelength due to the different emergent paths of each satellite. 相似文献
13.
H. C. Pant S. Sharma T. P. S. Nathan T. Desai 《Applied Physics A: Materials Science & Processing》1980,23(2):183-187
Optical energy balance in plasmas produced by irradiating solid targets by highpower laser pulses, has been experimentally
determined. The total light scattered has been measured as a function of the laser intensity and the irratiated spot diameter.
It has been found that the net light absorption does not depend on the laser intensity alone, but is also affected by the
irradiated spot area. It has also been observed that diffuse back reflection becomes a dominant loss mechanism at high incident
flux and small irradiated spot area. 相似文献
14.
Axial magnetic fields in laser-produced plasmas 总被引:1,自引:0,他引:1
Briand J Adrian V El Tamer M Gomes A Quemener Y Dinguirard JP Kieffer JC 《Physical review letters》1985,54(1):38-41
15.
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. 相似文献
16.
Xiaochang Ni K. K. Anoop X. Wang D. Paparo S. Amoruso R. Bruzzese 《Applied Physics A: Materials Science & Processing》2014,117(1):111-115
We investigated the ion laser-produced plasma plume generated during ultrafast laser ablation of copper and silicon targets in high vacuum. The ablation plasma was induced by ≈50 fs, 800 nm Ti:Sa laser pulses irradiating the target surface at an angle of 45°. An ion probe was used to investigate the time-of-flight profiles of the emitted ions in a laser fluence range from the ablation threshold up to ≈10 J/cm2. The angular distribution of the ion flux and average velocity of the produced ions were studied by moving the ion probe on a circle around the ablation spot. The angular distribution of the ion flux is well described by an adiabatic and isentropic model of expansion of a plume produced by laser ablation of solid targets. The angular distribution of the ion flux narrows as the laser pulse fluence increases. Moreover, the ion average velocity reaches values of several tens of km/s, evidencing the presence of ions with kinetic energy of several hundred eV. Finally, the ion flux energy is confined in a narrow angular region around the target normal. 相似文献
17.
J. P. Marques P. Indelicato C. I. Szabo F. Parente 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):179-184
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 相似文献
18.
Fujioka S Nishimura H Nishihara K Sasaki A Sunahara A Okuno T Ueda N Ando T Tao Y Shimada Y Hashimoto K Yamaura M Shigemori K Nakai M Nagai K Norimatsu T Nishikawa T Miyanaga N Izawa Y Mima K 《Physical review letters》2005,95(23):235004
Opacity effects on extreme ultraviolet (EUV) emission from laser-produced tin (Sn) plasma have been experimentally investigated. An absorption spectrum of a uniform Sn plasma generated by thermal x rays has been measured in the EUV range (9-19 nm wavelength) for the first time. Experimental results indicate that control of the optical depth of the laser-produced Sn plasma is essential for obtaining high conversion to 13.5 nm-wavelength EUV radiation; 1.8% of the conversion efficiency was attained with the use of 2.2 ns laser pulses. 相似文献
19.