共查询到20条相似文献,搜索用时 31 毫秒
1.
Dollar F Matsuoka T Petrov GM Thomas AG Bulanov SS Chvykov V Davis J Kalinchenko G McGuffey C Willingale L Yanovsky V Maksimchuk A Krushelnick K 《Physical review letters》2011,107(6):065003
By using temporal pulse shaping of high-contrast, short pulse laser interactions with solid density targets at intensities of 2 × 10(21) W cm(-2) at a 45° incident angle, we show that it is possible to reproducibly generate quasimonoenergetic proton and ion energy spectra. The presence of a short pulse prepulse 33 ps prior to the main pulse produced proton spectra with an energy spread between 25% and 60% (ΔE/E) with energy of several MeV, with light ions becoming quasimonoenergetic for 50 nm targets. When the prepulse was removed, the energy spectra was broad. Numerical simulations suggest that expansion of the rear-side contaminant layer allowed for density conditions that prevented the protons from being screened from the sheath field, thus providing a low energy cutoff in the observed spectra normal to the target surface. 相似文献
2.
P.?Gibbon M.?Ma?ek U.?Teubner W.?Lu M.?Nicoul U.?Shymanovich A.?Tarasevitch P.?Zhou K.?Sokolowski-Tinten D.?von?der?Linde 《Applied Physics A: Materials Science & Processing》2009,96(1):23-31
Recent theoretical and numerical studies of laser-driven femtosecond K
α
sources are presented, aimed at understanding a recent experimental campaign to optimize emission from thin coating targets.
Particular attention is given to control over the laser–plasma interaction conditions defined by the interplay between a controlled
prepulse and the angle of incidence. It is found that the x-ray efficiency for poor-contrast laser systems in which a large
preplasma is suspected can be enhanced by using a near-normal incidence geometry even at high laser intensities. With high
laser contrast, similar efficiencies can be achieved by going to larger incidence angles, but only at the expense of larger
x-ray spot size. New developments in three-dimensional modelling are also reported with the goal of handling interactions
with geometrically complex targets and finite resistivity. 相似文献
3.
M. Manclossi A. Guemnie-Tafo D. Batani V. Malka S. Fritzler E. Lefebvre 《辐射效应与固体损伤》2013,168(10-12):631-637
We report on some recent experimental results on proton production from ultra-intense laser pulse interaction with thin aluminium and plastic foil targets. These results were obtained at Laboratoire d'Optique Appliquée with the 100 TW ‘salle jaune’ laser system, delivering 35 fs laser pulses at 0.8 μm, reaching a maximum intensity on target of a few 1019 W/cm2. In such extreme interaction conditions, an intense and collimated relativistic electron current is injected from the plasma created on the laser focal spot into the cold interior of the target. Its transport through dense matter, ruled by both collisions and self-induced (electro-magnetic) field effects, is the driving mechanism for proton acceleration from the rear side of thin foils: when reaching and leaving the foil rear-side, the fast electrons create a large charge separation and a huge electrostatic field with a maximum value of few TV/m, capable of accelerating protons. A parametric study as a function of the laser driver and target parameters indicates an optimal value for target thickness, which strongly depends on the laser prepulse duration. In our experiments, we did irradiate targets of various materials (CH, Al, Au) changing the prepulse duration by using fast Pockels cells in the laser chain. CR-39 nuclear track detectors with Al filters of different thickness and a Thomson parabola were used to detect proton generation. The best results were obtained for 2 μm Al targets, leading to the generation of proton energies with energies up to 12 MeV. 相似文献
4.
We report the generation of ultrashort, hard-x-ray pulses from a liquid mercury target irradiated by 5 kHz laser pulses. The new x-ray source is designed for time-resolved x-ray absorption spectroscopy as well as imaging applications. This marks the first laser-driven plasma x-ray source that continuously recycles the target material, facilitating maintenance-free operation. Theoretical calculations show mercury targets emit shorter x-ray pulses than targets of lighter elements under identical illumination and x-ray detection conditions. 相似文献
5.
A. E. Bugrov S. Yu. Gus’kov V. B. Rozanov I. N. Burdonskii V. V. Gavrilov A. Yu. Gol’tsov E. V. Zhuzhukalo N. G. Koval’skii M. I. Pergament V. M. Petryakov 《Journal of Experimental and Theoretical Physics》1997,84(3):497-505
We have experimentally investigated the processes of laser light absorption and energy transfer in porous targets made of
“agar-agar” (C14H18O7) with an average density of 1–4 mg/cm3 illuminated by the focused beam of a neodymium laser with an intensity of 1014 W/cm2 within a pulse of duration 2.5 ns. Many important scientific and technical problems, e.g., inertial-confinement thermonuclear
fusion, the creation of lasers in the x-ray regime, and the modeling of astrophysical phenomena under laboratory conditions,
can be successfully addressed by using low-density porous media as components of such targets. In our experiments with porous
targets of variable density and thickness we used optical and x-ray diagnostic methods, which ensured that our measurements
were made with high temporal and spatial resolution. We show that a region forms within the porous target consisting of a
dense high-temperature plasma which effectively absorbs the laser radiation. Energy is transferred from the absorption region
to the surrounding layer of porous material at up to 2×107 cm/s. Experimental data are in good agreement with the predictions of our theoretical model, which takes into account the
specific features of absorption of laser radiation in a porous material and is based on representing the energy transfer within
the material as a hydrothermal wave.
Zh. éksp. Teor. Fiz. 111, 903–918 (March 1997) 相似文献
6.
A. É. Bugrov S. Yu. Gus’kov V. B. Rozanov I. N. Burdonskii V. V. Gavrilov A. Yu. Gol’tsov E. V. Zhuzhukalo N. G. Koval’skii V. N. Kondrashov M. I. Pergament V. M. Petryakov S. D. Tsoi 《Journal of Experimental and Theoretical Physics》1999,88(3):441-448
We have experimentally investigated the interaction of high-power neodymium laser pulses in the intensity range 1013–1014 W/cm2 with flat low-density (0.5–10 mg/cm3) agar-agar targets under conditions of interest for problems of inertial nuclear fusion. Optical and x-ray methods with high
temporal and spatial resolution were used to examine the dependence of absorption and scattering of the incident beam on the
initial mean density and thickness of the irradiated samples. We show that when a porous target is irradiated, a bulk absorption
layer of high-temperature plasma is produced inside the target whose dimensions are determined by the initial density of the
material. The time dependence and spectral composition of the harmonics 2ω
0 and 3ω
0/2 observed in the plasma-scattered radiation are measured. A theoretical model is developed that describes the interaction
of high-power laser pulses with a porous medium. Predictions of the model, based on the hypothesis of two stages of homogenization
of the target material—a fast stage (0.1–0.3 ns) and a slow stage (1–3 ns), are in good agreement with the experimental data.
Zh. éksp. Teor. Fiz. 115, 805–818 (March 1999) 相似文献
7.
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
8.
Theoretical study of Ni-like Ag 13.9nm TCE x-ray laser driven by two picosecond pulses 总被引:1,自引:0,他引:1
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The Ni-like Ag 13.9nm x-ray laser has been previously demonstrated
that the higher gain near critical surface contributes little to the
amplification of the x-ray laser because of severe refraction. In
this paper, the transient collision excitation (TCE) Ni-like Ag
13.9nm x-ray laser is simulated, driven by two 3ps short pulse
preceded by a 330ps long prepulse, optimization of the peak to
peak delay time of the two short pulses is made to get the best
results. Simulation indicates that by producing lowly ionized
preplasma with smoothly varying electron density, it is possible to
decrease electron density gradient in higher density region, and
thus higher gains near this region could be utilized, and if the
main short pulse is delayed by 900ps, local gains where electron
density larger than ~ 4×1020cm-3 could be utilized. 相似文献
9.
Kulcsar G AlMawlawi D Budnik FW Herman PR Moskovits M Zhao L Marjoribanks RS 《Physical review letters》2000,84(22):5149-5152
We describe the optical, radiative, and laser-plasma physics of a new type of nanostructured surface especially promising as a very high absorption target for high-peak-power subpicosecond laser-matter interaction. This oriented-nanowire material, irradiated by 1 ps pulses at intensities up to 10(17) W cm(-2), produces picosecond soft x-ray pulses 50x more efficiently than do solid targets. We compare this to "smoke" or metallic clusters, and solid nanogroove-grating surfaces; the "metal-velvet" targets combine the high yield of smoke targets with the brief emission of grating surfaces. 相似文献
10.
Akli KU Hansen SB Kemp AJ Freeman RR Beg FN Clark DC Chen SD Hey D Hatchett SP Highbarger K Giraldez E Green JS Gregori G Lancaster KL Ma T MacKinnon AJ Norreys P Patel N Pasley J Shearer C Stephens RB Stoeckl C Storm M Theobald W Van Woerkom LD Weber R Key MH 《Physical review letters》2008,100(16):165002
The heating of solid targets irradiated by 5 x 10(20) W cm(-2), 0.8 ps, 1.05 microm wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo, and V. A surface layer is heated to approximately 5 keV with an axial temperature gradient of 0.6 microm scale length. Images of Ni Ly(alpha) show the hot region has 100 G bar light pressure compresses the preformed plasma and drives a shock into the solid, heating a thin layer. 相似文献
11.
Pressed pepsin pellets used as targets were ablated with the pulses of the Nd-YAG laser. The activity of the pepsin thin layer, deposited on a glass substrate, was successfully detected by analyzing the proteolytic degradation areas on the polyacrylamide gel (PA-gel) copolymerized with albumin from the hen egg white (ovalbumin), used as an enzymatic substrate. 相似文献
12.
V. S. Belyaev V. I. Vinogradov A. S. Kurilov A. I. Magunov A. P. Matafonov T. A. Pikuz I. Yu. Skobelev A. Ya. Faenov 《Journal of Experimental and Theoretical Physics》2003,96(5):897-903
X-ray emission spectra of the plasma created at the surface of magnesium, aluminum, copper, and zinc targets heated by 1-ps laser pulses with a peak power density of up to 1016 W/cm2 were measured. The effect of a picosecond prepulse on the spectra was studied for various power densities and intensity contrasts of the main laser pulse. It is established that the emission spectra of laser plasmas are weakly affected by a change from 105 to 107 in the main pulse contrast relative to the first prepulse. Variations in the parameters of emission from aluminum and magnesium plasmas were calculated using relative intensities and widths of the resonance lines of H-and He-like ions and their two-electron satellite peaks. 相似文献
13.
P. V. Nickles M. Schnuerer M. P. Kalachnikov T. Schlegel A. Y. Faenov 《Optical and Quantum Electronics》1996,28(3):229-239
Highly intense picosecond and subpicosecond laser pulses interacting with solids can create hot and dense plasmas which emit x-ray pulses in a broad spectral range from 100 eV up to MeV. The duration of these x-ray pulses depends on the transient behaviour of the relaxation and recombination mechanisms, as well as on the lifetime of energetic electrons produced via nonlinear processes in the plasma. This paper reports experiments using a 1.5-ps laser pulse with high constrast ratio (up to 1010) and intensities up to 1018 W cm-2 irradiating solid targets. Both the line spectrum characteristics of a magnesium plasma, recorded using crystal spectrometers with high spectral resolution, and kinetic calculations have allowed the deduction of plasma parameters in the process of plasma evolution. In addition, hard x-ray pulses from a tantalum plasma were measured and their scaling was explained as bremsstrahlung emission from energetic electrons. Absolute dose values of x-ray pulses are given. 相似文献
14.
Mackinnon AJ Sentoku Y Patel PK Price DW Hatchett S Key MH Andersen C Snavely R Freeman RR 《Physical review letters》2002,88(21):215006
MeV-proton production from solid targets irradiated by 100-fs laser pulses at intensities above 1x10(20) W cm(-2) has been studied as a function of initial target thickness. For foils 100 microm thick the proton beam was characterized by an energy spectrum of temperature 1.4 MeV with a cutoff at 6.5 MeV. When the target thickness was reduced to 3 microm the temperature was 3.2+/-0.3 MeV with a cutoff at 24 MeV. These observations are consistent with modeling showing an enhanced density of MeV electrons at the rear surface for the thinnest targets, which predicts an increased acceleration and higher proton energies. 相似文献
15.
Zhengtao Qin Jinmyoung Joo Luo Gu Michael J. Sailor 《Particle & Particle Systems Characterization》2014,31(2):252-256
Size‐controlled porous silicon‐based nanoparticles are prepared by pulsed electrochemical etching of single crystal silicon wafers, followed by ultrasonic fracture of the freestanding porous layer. When high‐current density pulses are applied periodically during the porous layer etching process, a porous multilayer results in which porous layers are separated by thin layers of much higher porosity. Ultrasonic fracture selectively cleaves the porous film along these high‐porosity perforations, providing greater size control and improved yields (by 5x) of the resulting porous nanoparticles. The effect of pulse width and repetition rate is systematically studied: tunability of the average nanoparticle size in the range 160–350 nm is demonstrated. 相似文献
16.
Short-laser-pulse-driven emission of energetic ions into a solid target from a surface layer spalled by a laser prepulse 总被引:1,自引:0,他引:1
A.G. Zhidkov L.V. Zhigilei A. Sasaki T. Tajima 《Applied Physics A: Materials Science & Processing》2001,73(6):741-747
An efficient emission of picosecond bunches of energetic protons and carbon ions from a thin layer spalled from a organic
solid by a laser prepulse is demonstrated numerically. We combine the molecular dynamics technique and multi-component collisional
particle-in-cell method with plasma ionization to simulate the laser spallation and ejection of a thin (∼20–30 nm) solid layer
from an organic target and its further interaction with an intense femtosecond laser pulse. In spite of its small thickness,
a layer produced by laser spallation efficiently absorbs ultrashort laser pulses with the generation of hot electrons that
convert their energy to ion energy. The efficiency of the conversion of the laser energy to ions can be as high as 20%, and
10% to MeV ions. A transient electrostatic field created between the layer and surface of the target is up to 10 GV/cm.
Received: 13 March 2001 / Accepted: 20 March 2001 / Published online: 20 June 2001 相似文献
17.
X-ray spectroscopic observations of a superdense plasma in nanoparticles irradiated by superintense femtosecond laser radiation 总被引:1,自引:0,他引:1
A. Ya. Faenov T. A. Pikuz I. Yu. Skobelev A. I. Magunov V. P. Efremov M. Servol F. Quéré M. Bougeard P. Monot Ph. Martin M. Francucci G. Petrocelli P. Audebert 《JETP Letters》2004,80(12):730-733
The interaction of femtosecond laser pulses with SiO2 aerogel targets has been analyzed by x-ray spectroscopic methods. The use of an aerogel target with transparent grains makes it possible to considerably reduce the requirements on laser-pulse contrasts for which heating occurs without the formation of a preplasma. A nanoplasma with a density sevenfold higher than the solid-state density has been detected. 相似文献
18.
Brown CR Hoarty DJ James SF Swatton D Hughes SJ Morton JW Guymer TM Hill MP Chapman DA Andrew JE Comley AJ Shepherd R Dunn J Chen H Schneider M Brown G Beiersdorfer P Emig J 《Physical review letters》2011,106(18):185003
The heating of solid foils by a picosecond time scale laser pulse has been studied by using x-ray emission spectroscopy. The target material was plastic foil with a buried layer of a spectroscopic tracer material. The laser pulse length was either 0.5 or 2 ps, which resulted in a laser irradiance that varied over the range 10(16)-10(19) W/cm(2). Time-resolved measurements of the buried layer emission spectra using an ultrafast x-ray streak camera were used to infer the density and temperature conditions as a function of laser parameters and depth of the buried layer. Comparison of the data to different models of electron transport showed that they are consistent with a model of electron transport that predicts the bulk of the target heating is due to return currents. 相似文献
19.
Pulse forming networks for high current particle beam fusion accelerators must produce fast rise time, low jitter, low prepulse, and high voltage power pulses. Conventional water dielectric switching can provide the required rise time and jitter, but has limitations on prepulse and output voltage. A high power density, low prepulse, pulse forming line (PFL) configuration with self-breakdown water dielectric switches is presented. The design parameters and the results of switching experiments are described. 相似文献
20.
K. V. Khishchenko A. A. Charakhch’yan V. V. Milyavskii V. E. Fortov A. A. Frolova L. V. Shurshalov 《Russian Journal of Physical Chemistry B, Focus on Physics》2007,1(6):612-622
The effect of amplification of moderate-intensity converging shock waves in porous media with decreasing initial density, revealed by numerically solving the hydrodynamics equations, was demonstrated for ID converging waves and for a 2D problem of the compression of porous material in conical solid targets. The latter problem was also treated within the framework of the simplest model of dynamic deformation of solids, with consideration given to shear stresses. The calculation results for porous graphite, aluminum, and Teflon samples are presented. Both closed targets and targets with an outlet orifice were considered. When modeling the intense shock loading of graphite, its transformation into diamond was taken into account. 相似文献