共查询到20条相似文献,搜索用时 31 毫秒
1.
V. A. Andronov S. A. Bel’kov A. V. Bessarab I. N. Voronich S. G. Garanin A. A. Gorbunov V. N. Derkach G. V. Dolgoleva A. I. Zaretskii V. M. Izgorodin B. N. Ilyushechkin G. A. Kirillov G. G. Kochemasov Yu. V. Kuratov V. I. Lazarchuk V. A. Lebedev V. M. Murugov L. S. Mkhitar’yan A. V. Okutin S. I. Petrov A. V. Pinegin N. N. Rukavishnikov A. N. Razin A. V. Ryadov A. V. Senik N. A. Suslov S. A. Sukharev V. A. Tokarev 《Journal of Experimental and Theoretical Physics》1997,84(3):485-488
The results of the first experiments devised to investigate the mixing of thin layers of Al and Au during the laser acceleration
of flat three-layer targets of Si (5 μm), Al (2 μm), and Au (0.05–0.26 μm) by radiation converted to the second harmonic from the Iskra-4 iodine laser with an intensity of 4×1013−7×1013 W/cm2 (τ
0.5∼1 ns), which acts on the Si side of the target. A method for detecting the occurrence of mixing is developed. It is established
that under the experimental conditions the thickness of the mixing region is at least ∼0.15 μm. The results of a theoretical analysis of the evolution of the disturbances leading to mixing are presented.
Zh. éksp. Teor. Fiz. 111, 882–888 (March 1997)
Deceased. 相似文献
2.
N. G. Borisenko A. A. Akunets A. M. Khalenkov D. Klir V. Kmetik E. Krousky J. Limpouch K. Masek Yu. A. Merkuliev M. Pfeifer V. G. Pimenov J. Ullschmied 《Journal of Russian Laser Research》2007,28(6):548-566
The velocities of energy transport in an undercritical plasma of polymer aerogel with and without copper nanoparticles were
measured. Transmission of the laser light through targets of different thicknesses such as submicron three-dimensional polymer
networks with densities below the critical value (0.13–0.52 N
cr) for a wavelength of 0.438 μm and intensity of (3–7)·1014 W/cm2 at a half-height pulse duration of 0.32 ns was studied. The transfer of a heating laser radiation was registered on the rear
side of the target. It ranged from a level of ∼0.5% for the thickness of a low-density layer of 400 μm and density of 9 mg/cm3 (mass per unit square of 0.36 mg/cm2) up to 50–60% for a thickness of 100 μm and density of 2.25 mg/cm3 (mass per unit square of 0.02 mg/cm2). The time dependences of the optical emission from the rear side of the targets were measured. They appear to be indicative
of the plasma dynamics in two-layer targets (polymer foam on Al foil) and enable the estimation of the absorption depth for
the laser light in an undercritical plasma.
__________
Translated from Preprint No. 8 of the P. N. Lebedev Physical Institute, Moscow (2007). 相似文献
3.
A. V. Andreev V. M. Gordienko A. B. Savel’ev E. V. Tkalya A. M. Dykhne 《JETP Letters》1997,66(5):331-335
It is shown that in a plasma produced on the surface of a sample consisting of a natural mixture of mercury isotopes, ∼104−105
201Hg nuclei can be excited into the low-lying isomeric level 1/2− (1.561 keV) by an ultrashort laser pulse with energy ≈1 J, duration ≈200 fs, and intensity ≈1016 W/cm2 and the lifetime of the level can be determined. Possible mechanisms leading to the excitation of 201Hg nuclei by photons and electrons in a dense, hot plasma are examined and the cross sections of the processes are estimated.
Schemes for detecting the effect are proposed.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 5, 312–316 (10 September 1997) 相似文献
4.
The nonlinear scattering of an ultrashort laser pulse by free electrons is considered. The pulse is described in the “Mexican
hat” wavelet basis. The equation of motion for a charged particle in the field of a plane electromagnetic wave has an exact
solution allowing, together with the instant spectrum approximation, the calculation of the intensity of nonlinear Thomson
scattering for a high-intensity laser pulse. The spectral distribution of scattered radiation for the entire pulse duration
is found by integrating with respect to time. The maximum of the emission spectrum of a free electron calculated in 1019–1021 W/cm2 fields lies in the UV spectral region between 3 and 12 eV. A part of the continuous spectrum achieves high photon energies.
One percent of the scattered energy for the field intensity 1020 W/cm2 is concentrated in the range ħω > 2.7 × 102 eV, for a field intensity of 1021 W/cm2 in the range ħΩ > 7.9 × 102 eV, and for an intensity of 1022 W/cm2 in the range ħΩ > 2.45 × 105 eV. These results allow us to estimate nonlinear scattering as a source of hard X-rays. 相似文献
5.
We report here an experimental study of the ionic keV X-ray line emission from magnesium plasma produced by laser pulses of
three widely different pulse durations (FWHM) of 45 fs, 25 ps and 3 ns, at a constant laser fluence of ∼1.5 × 104 J cm − 2. It is observed that the X-ray yield of the resonance lines from the higher ionization states such as H- and He-like ions
decreases on decreasing the laser pulse duration, even though the peak laser intensities of 3.5 × 1017 W cm − 2 for the 45 fs pulses and 6.2 × 1014 W cm − 2 for the 25 ps pulses are much higher than 5 × 1012 W cm − 2 for the 3 ns laser pulse. The results were explained in terms of the ionization equilibrium time for different ionization
states in the heated plasma. The study can be useful to make optimum choice of the laser pulse duration to produce short pulse
intense X-ray line emission from the plasma and to get the knowledge of the degree of ionization in the plasma. 相似文献
6.
A. Ya. Faenov S. A. Pikuz A. G. Zidkov I. Yu. Skobelev P. S. Komarov O. V. Chefonov S. V. Gasilov A. V. Ovchinnikov 《JETP Letters》2010,92(6):375-378
The characteristics of X rays of a laser plasma generated in the interaction of a femtosecond pulse with solid targets in
an air atmosphere have been investigated. It has been shown that the mechanism for the generation of X rays in the interaction
of short intense laser pulses with solid targets in a gas atmosphere is attributed to the generation of fast electrons in
the region of the filamentation of a laser pulse. It has been proven experimentally that under such conditions, the solid
target irradiated by laser radiation of even a low density of about 1015 W/cm2 very efficiently emits ∼10-keV photons. It has been shown theoretically that the maximum energy of accelerated electrons
can reach ɛmax ∼ 100–200 keV under these conditions. This means that the proposed method can provide characteristic radiation with the energy
of photons much higher than 10 keV. 相似文献
7.
Z. Tóth B. Hopp J. Klebniczki N. Kresz Z. Bor D. Anglos C. Kalpouzos C. Fotakis 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1287-1290
High gradient laser plasma is formed by focused KrF laser pulses (248.3 nm, 450 fs, 1013 W/cm2) on liquids (water, styrene) and solids (silicon, aluminum, and polyimide). The hydrodynamic expansion of the plasma was studied by measuring the blue Doppler-shift of reflected probe pulses which was produced by a delayed dye laser (496.6 nm, 450 fs). The Doppler-shift corresponds to the velocity of the reflecting surface of the plasma which is defined by the critical electron density. Expansion is investigated as a function of delay time and laser intensity. The reflecting surface of the plasma accelerates over 1–2 ps after the onset of the ablating laser pulse. With increasing intensity up to 2×1013 W/cm2 the maximum average velocities are monotonously increasing up to 1–2×105 m/s. PACS 52.38.Kd; 52.50.Jm, 52.70.Kz 相似文献
8.
Md. Salimullah R. R. Sharma V. K. Tripathi 《Applied Physics A: Materials Science & Processing》1981,25(3):361-365
Using the fluid model for the nonlinear response of ions, we have studied the nonlinear scattering of an electromagnetic ion
cyclotron wave off the ion acoustic wave in a plasma. The low frequency nonlinearity arises through the parallel ponderomotive
force on ions and the high frequency nonlinearity arises through the nonlinear current density of ions. For a typical nonisothermal
plasma (T
e/T
i∼10) the threshold for this instability in a uniform plasma is ∼1mW/cm2. At power densities ≳102 W/cm2, the growth rate for backscatter turns out to be ∼104s−1. 相似文献
9.
M. Schnürer S. Ter-Avetisyan H. Stiel U. Vogt W. Radloff M. Kalashnikov W. Sandner P.V. Nickles 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):331-335
Using 50 fs ( ∼ 2×1018 W/cm2) and 2 ps ( ∼ 5×1016 W/cm2) pulses from a Ti:Sa multi-TW laser at 800 nm wavelength large Xe-clusters ( 105...106 atoms per cluster) have been excited. Absolute yield measurements of EUV-emission in a wavelength range between 10 nm and
15 nm in combination with cluster target variation were carried out. The ps-laser pulse has resulted in about 30% enhanced
and spatially more uniform EUV-emission compared to fs-laser excitation. Circularly polarized laser light instead of linear
polarization results in enhanced emission which is probably caused by electrons gaining higher energies by the polarization
dependent optical field ionization process. An absolute emission efficiency at 13.4 nm of up to 0.8% in 2π sr and 2.2% bandwidth
has been obtained.
Received 11 January 2001 and Received in final form 27 March 2001 相似文献
10.
T. Palchan S. Eisenmann A. Zigler D. Kaganovich R.F. Hubbard M. Fraenkel D. Fisher Z. Henis 《Applied physics. B, Lasers and optics》2006,83(2):219-223
Energetic electron bunches were generated by irradiating a solid tungsten wire 13 μm wide with 50 femtosecond pulses at an intensity of ∼3×1018 W/cm2. The electron yield, energy spectrum and angular distribution were measured. These energetic electron bunches are suitable for injection into a laser driven plasma accelerator. An all-optical electron injector based on this approach could simplify timing and alignment in future laser-plasma accelerator experiments. PACS 41.75.Ht; 41.75.Lx; 52.38.Kd; 52.38.Ph 相似文献
11.
Amin Abdolvand Robert W. Lloyd Marc J. J. Schmidt David J. Whitehead Zhu Liu Lin Li 《Applied Physics A: Materials Science & Processing》2009,95(2):447-452
We present results on the growth of highly organised, reproducible, periodic microstructure arrays on a stainless steel substrate
using multi-pulsed Nd:YAG (wavelength of 1064 nm, pulse duration of 7 ns, repetition rate of 25 kHz, beam quality factor of
M
2∼1.5) laser irradiation in standard atmospheric environment (room temperature and normal pressure) with laser spot diameter
of the target being ∼50 μm. The target surface was irradiated at laser fluence of ∼2.2 J/cm2 and intensity of ∼0.31×109 W/cm2, resulting in the controllable generation of arrays of microstructures with average periods ranging from ∼30 to ∼70 μm, depending
on the hatching overlap between the consecutive scans. The received tips of the structures were either below or at the level
of the original substrate surface, depending on the experimental conditions. The peculiarity of our work is on the utilised
approach for scanning the laser beam over the surface. A possible mechanism for the formation of the structures is proposed. 相似文献
12.
The mechanism of generation of terahertz radiation upon irradiation of a target by short (∼ 0.1 ns) high-intensity laser pulses
(I ∼ 1018−1019 W cm−2) is investigated by numerical simulation using the relativistic electromagnetic PIC code. The interaction of such a pulse
with the target, a plasma is formed on it. Electrons emitted from the plasma form a virtual cathode whose oscillations are
determined not only by their self-field, but also by the field of ions of the plasma. Generation occurs in the terahertz frequency
range with the efficiency thrice as high as in the absence of ions (i.e., with traditional reditron generation mechanism).
The explanation for this effect is also given. 相似文献
13.
A sequential three-dimensional (3D) particle-in-cell simulation code PICPSI-3D with a user friendly graphical user interface
(GUI) has been developed and used to study the interaction of plasma with ultrahigh intensity laser radiation. A case study
of laser–plasma-based electron acceleration has been carried out to assess the performance of this code. Simulations have
been performed for a Gaussian laser beam of peak intensity 5 × 1019 W/cm2 propagating through an underdense plasma of uniform density 1 × 1019 cm − 3, and for a Gaussian laser beam of peak intensity 1.5 × 1019 W/cm2 propagating through an underdense plasma of uniform density 3.5 × 1019 cm − 3. The electron energy spectrum has been evaluated at different time-steps during the propagation of the laser beam. When the
plasma density is 1 × 1019 cm − 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~14 MeV, with an energy spread of ±7 MeV.
On the other hand, when the plasma density is 3.5 × 1019 cm − 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~23 MeV, with an energy spread of ±7.5 MeV. 相似文献
14.
This paper presents the results of experiments on the generation of pulsed γ radiation of average photon energy ∼1.2 MeV and
duration ≤20 ns on the MIG system with a plasma opening switch. Operating modes with a maximum dose downstream of the anode
of (1–2)·1013 and 1012 R/s over an area of 2–3 and 100 cm2 are obtained, respectively.
Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh
Uchebnykh Zavedenii, Fizika, No. 12, pp. 26–30, December, 1999. 相似文献
15.
An experimental study is presented on measurements of optical spectrum of the laser light scattered from solid surface irradiated
by Ti:sapphire laser pulses up to an intensity of 1.2 × 1018 W cm−2. The spectrum has well-defined peaks at wavelengths corresponding to 2ω and 3/2ω radiations. The spectral features vary with the laser intensity and show blue-shift with increasing laser intensity. At a
constant laser fluence, the spectrum is red-shifted with increasing laser pulse duration. The observed results are explained
in terms of the density scale length variation of the plasma and laser chirp. 相似文献
16.
A new mechanism of a “Coulomb explosion,” where ions are accelerated by the electric field separating charges at the magnetic
Debye radius r
B∼B/4πen
e, is proposed on the basis of a nonquasineutral model of electronic vortices in a magnetic field. It is shown by means of
numerical calculations that in the process of acceleration of the ions a collisionless shock wave, whose front has an effective
width of the order of δ∼r
B, determined by the breakdown of quasineutrality, is formed in a time of the order of ω
pi
−1
, where ωpi is the ion plasma frequency. The origin of such explosive dynamics is the formation of “holes” in the electron density at
characteristic times of the order of ω
pe
−1
(ωpe is the electronic plasma frequency) as a result of the generation of electronic vorticity by the Weibel instability of an
electromagnetic wave. Calculations for a laser pulse with intensity J∼6×1018 W/cm2 show that the ions expand in the radial direction with velocities up to 3.5×108 cm/s.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 10, 669–674 (25 November 1999) 相似文献
17.
A.R. Präg F. Löwenthal R. Tommasini J.E. Balmer 《Applied physics. B, Lasers and optics》1998,66(5):561-566
2 . By using a 0.7% prepulse that precedes the main pulse by 5 ns and applying a total pump energy of 100 J or less, the J=0-1
lasing is at least one order of magnitude higher than the non-lasing background. For the 32.6-nm line of Ti, the 25.5-nm line
of Fe, and the 23.1-nm line of Ni, gain coefficients of (±) 4.20.4cm-1, (±) 3.90.3cm-1, and (±) 3.60.6cm-1, respectively, were measured for 2.4-cm-long curved targets, resulting in gain–length products of ∼10. Angle-resolved spectra
indicate a beam divergence of 3 mrad (FWHM), typically. The space-resolved spectra show that the J=0-1 lasing lines are emitted
from an approximately 60-μm-wide (FWHM) plasma region, whereas the nearby continuum emission is produced in a considerably
broader plasma region of ∼250 μm. Lasing at 25.5 nm in neon-like iron was observed at a pump power as low as 180 GW (∼9 TW/cm2), with, however, considerable shot-to-shot scatter in the absolute laser output.
Received: 5 September 1997/Revised version: 10 November 1997 相似文献
18.
The spatial characteristic of an aluminum laser-induced plasma are studied at a laser radiation intensity of (3.8–4.8) × 108 W/cm2 and an air residual pressure of 6.7–133.3 Pa. It is found that the duration of the aluminum plasma glow is 50 μs and decreases
with decreasing laser power output. The glow intensity reaches a maximum at t = 1.4 μs and rises with laser energy. Typical sizes of the emitting area on the laser torch are determined. 相似文献
19.
T. Gasmi H.A. Zeaiter G. Ropero A. González Urena 《Applied physics. B, Lasers and optics》2000,71(2):169-175
This paper presents the construction, use and characterisation of a laser-induced sealed plasma shutter to clip off the nitrogen
pulse tail of a CO2-TEA laser-based lidar dial system. Investigation of the optimum gas filling pressure, temporal profile of the clipped pulse,
and the laser threshold power intensities to achieve ionisation growth and breakdown in helium, argon, and nitrogen are also
presented. Values of these power density thresholds lie between 3×1011 W cm-2–5×1012 W cm-2, 2×1011 W cm-2–2×1012 W cm-2 and 3×1013 W cm-2–2×1014 W cm-2 for helium, argon, and nitrogen, respectively. The range resolution attainable with the present clipped pulses is 15 m, which
is 30 times better than that readily obtained with the nitrogen-tailed pulses. Field measurements of the lidar returns with
the clipped pulse from a co-operative target are presented.
Received: 27 December 1999 / Revised version: 11 February 2000 / Published online: 27 April 2000 相似文献
20.
K. G. Shaynurova S. A. Bakhramov A. M. Kokhkharov U. K. Makhmanov E. A. Zakhidov 《Journal of Applied Spectroscopy》2012,78(6):802-810
Features of light pulse propagation and nonlinear optical transformation of the spectrum generated by titanium-sapphire laser
pulses (τ0.5 = 27 fs, λ0 = 790 nm) have been studied experimentally in a 50-cm cylindrical hollow waveguide (microcapillary with 280-μm diameter core)
filled with gaseous molecular nitrogen and helium. Stable guided propagation of light pulses with an intensity of ~1.5⋅1014 W/cm2 in the fundamental EH11 mode of the gas-filled capillary has been demonstrated. Exact focusing of the laser light made it possible to obtain rather
high relative (≥95%) and absolute (~60%) energy transmission efficiencies for the pulses at gas pressures equal to or lower
than 760 Torr. A method to determine the nonlinear phase shift of the pulses has been proposed. Values of the nonlinear refractive
index n2 ≈ 4.5⋅10–23 cm2/(W⋅Torr) (N2) and n2 ≈ 2.8⋅10–23 cm2/(W⋅Torr) (He) have been found. A short-wavelength shift in addition to the Kerr nonlinearity has been shown to be contributed
by the generated electron plasma at high pulse intensities (≥1014 W/cm2). 相似文献