共查询到20条相似文献,搜索用时 25 毫秒
1.
G. Ferrante M. Zarcone S.A. Uryupin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):109-116
The reflection of a test electromagnetic wave normally impinging on a plasma surface is investigated within the formalism
of the surface impedance. The plasma is assumed to possess an anisotropic two-temperature bi-Maxwellian electron velocity
distribution function. The linearly polarized impinging wave during reflection transforms into an elliptically polarized one,
the degree of ellipticity depending on the electron temperature anisotropy. Polarization modifications of the reflected wave
are particularly important in the conditions of the anomalous skin-effect, when the influence of the wave magnetic field on
the electron kinetics in the skin layer is strong. Relations are reported connecting the reflected wave basic parameters to
those of the reflecting plasma surface, making possible, through the experimental determination of the reflected wave characteristics,
to find the plasma electron concentration and the two effective temperatures.
Received 21 May 2002 / Received in final form 21 August 2002 Published online 6 November 2002
RID="a"
ID="a"e-mail: zarcone@unipa.it 相似文献
2.
V. S. Lisitsa A. A. Skovoroda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(3):571-574
Perspectives of magnetic confinement for the increase of life times of laser
plasmas generated by femtosecond laser pulses are considered. Possibilities
that are provided by miniature magnetic cusp configurations with magnetic
fields of moderate intensities (of order of Teslas) are investigated. The
construction of micro-traps with permanent magnets, making it possible to
increase neutron yield, seems to be very simple and possible for most modern
“table top" laser experiments. 相似文献
3.
M.A. Lebeault J. Viallon J. Chevaleyre C. Ellert D. Normand M. Schmidt O. Sublemontier C. Guet B. Huber 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):233-242
We exposed small size-controlled lead clusters with a few hundreds of atoms to laser pulses with peak intensities up to 1015 W cm-2 and durations between 60 fs to 2.5 ps. We measured kinetic energies and ionic charge of fragments as a function of the laser
intensity and pulse duration. Highly charged Pbn+ ions up to n = 26 have been detected presenting kinetic energies up to 15 keV. For comparison with our experimental results, we have performed
simulations of the laser coupling with a cluster-sized lead nanoplasma using a qualitative model that was initially proposed
by Ditmire and co-workers at LLNL for the case of rare gas clusters. From these simulations we conclude that two mechanisms
are responsible for the explosion dynamics of small lead clusters. As already observed for large rare gas clusters (n = 106), fragments with charge states below +10 are driven by Coulomb forces, whereas the higher charged fragments are accelerated
by hydrodynamic forces. The latter mechanism is a direct consequence of the strong laser heating of the electron cloud in
the nanoplasma arising from a plasmon-like resonance occurring at n
e = 3n
c. In order to obtain an optimized laser-nanoplasma coupling, our results suggest that the plasma resonance should occur at
the peak intensity of the laser pulse. Due to inertial effects, even for such small-sized clusters, the observed optimum pulse
duration is in the order of 1 ps which is in good agreement with our theoretical results.
Received 18 March 2002 Published online 19 July 2002 相似文献
4.
D. Batani F. Strati B. Telaro Th. Löwer T. Hall A. Benuzzi-Mounaix M. Koenig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):99-107
In this paper we describe the quality requirements that a shock wave must fulfil to make equation of state (EOS) measurements
possible: planarity, no-preheating and stationarity of the shock. Experimental measurements have been performed at the Max
Planck Institut für Quantenoptik (Garching). We also present simple analytical models that allow to verify shock stationarity
and absence of preheating.
Received 17 June 2002 Published online 21 January 2003
RID="a"
ID="a"e-mail: batani@mib.infn.it
RID="b"
ID="b"Present address: Pro-beam, Behrinsta?e 6, 85152 Planegg b. München, Germany.
RID="c"
ID="c"UMR 7605 相似文献
5.
D. Batani C. Bleu Th. Löwer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):231-243
In this paper we analyze the use of phase plates to obtain homogeneous laser intensity profiles. We studied the dependence
of intensity distribution on phase plates characteristics, we obtained analytical solution for the intensity profile in the
focal plane for plane waves and developed a numerical simulator to calculate the intensity distribution with a generic initial
beam and at any propagation plane. We defined criteria to evaluate the quality of profiles produced by different phase plates.
Finally we compared experimental results obtained at the Max-Planck Institut für Quantenoptik of Garching with our numerical
simulations.
Received 23 July 2001 and Received in final form 8 January 2002 相似文献
6.
G. L. Chen H. Y. Lu C. Wang J. S. Liu R. X. Li G. Q. Ni Z. Z. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):303-307
We propose a plasma channel scheme to obtain an improved
table-top laser driven fusion neutron yield as a result of explosions of
large deuterium clusters irradiated by an intense laser pulse. A cylindrical
plasma channel is created by two moderate intensity laser prepulses at the
edge of a deuterium cluster jet along which an intense main laser pulse
propagates several nanoseconds later. With the aid of this plasma channel,
the main laser pulse will be allowed to deposit its energy into the central
region of the deuterium gas jet where the cluster sizes are larger and the
atomic density is higher. The plasma channel formation and its impact on the
deuterium ion energy spectrum and the consequent fusion neutron yield have
been investigated. The calculated results show that a remarkable increase of
the table-top laser driven fusion neutron yield would be expected. 相似文献
7.
D. Batani C. Botto M. Moret M. Milani G. Lucchini K. Eidmann F. Cotelli C. Lora Lamia Donin G. Poletti T. Ford A. Stead 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):167-179
In this paper the results of an experiment on soft X-ray contact microscopy using a laser-plasma source are presented. A resolution
of 50 nm has been achieved imaging pig sperm cells, while other specimens, such as algae and yeast cells, showed internal
details, proving the technique to be a powerful tool for biological investigations. Original biological information has been
obtained and the conditions for optimal image formation have been studied.
Received 5 June 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: batani@mib.infn.it 相似文献
8.
S. Borodziuk A. Kasperczuk T. Pisarczyk S. Yu. Gus'kov J. Ullschmied E. Krousky K. Masek M. Pfeifer K. Rohlena J. Skala M. Kalal J. Limpouch P. Pisarczyk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):311-317
Efficiency studies of laser driven thin metal disks
acceleration using the first harmonic (λ1=1.315 μm) of
the Prague Asterix Laser System (PALS) and subsequent craters creation
produced by collisions of these disks with massive targets are presented.
Several different disks made of aluminium and copper foils with diameters of
300 μm and 600 μm and thicknesses of 11 μm (Al) and 3.6 μ
m (Cu) were employed. Disks were placed at the distance of either 100 μ
m or 300 μm in front of aluminium massive targets. The following
irradiation conditions were used: the laser beam energy of 120 J, the focal
spot diameter of 200 μm, and the pulse duration of 0.4 ns (FWHM). A
three-frame interferometric system was employed to determine electron
density distributions in plasma corona. Shape and volume of craters were
obtained by crater replica technology and microscopy measurements. The aim
of these investigations was to analyse conditions leading to the most
effective energy transfer in the process of collision of the accelerated
disks with solid targets. The overall efficiency of these processes was
characterized by the volume of craters produced in such targets. 相似文献
9.
T. Döppner J. P. Müller A. Przystawik J. Tiggesbäumker K.-H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):261-266
Silver clusters embedded in helium nanodroplets are
exposed to intense femtosecond laser pulses (1013 - 1016 W/cm2).
The signal of highly charged (q≤11) atomic fragments is maximized by
delayed plasmon enhanced ionization using stretched laser pulses. Further
details with respect to the dynamics of the charging process can be obtained,
when the intensity distribution within the laser focus is taken into
account. For the first time, the z-scan method is applied to clusters
which offers a route to investigate the explicit dependence of the ion signals
with respect to the laser intensity. By taking advantage of the volumetric
weighting effect ionization thresholds are determined, yielding values well
below 1014 W/cm2 for Agq+ ions with q≤11. 相似文献
10.
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
11.
B. Ziaja A. R.B. de Castro E. Weckert T. Möller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):465-480
We apply Boltzmann equations for modelling the radiation damage in samples
irradiated by photons from free electron lasers (FELs). We test this method
in a study case of a spherically symmetric xenon cluster irradiated with
VUV FEL photons. Qualitative agreement between the model predictions and experimental data is found. The results obtained
demonstrate the potential of the Boltzmann method for describing the complex and non-equilibrium dynamics of samples exposed
to FEL radiation. 相似文献
12.
T. Döppner S. Teuber Th. Diederich Th. Fennel P. Radcliffe J. Tiggesbäumker K. H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):157-160
Lead clusters are exposed to strong femtosecond light
pulses. The dependence of the recoil energy on the charge state
of the atomic ion is now investigated using a new detection
setup, i.e., a Thomson
analyser. First results show that in contrast to laser-induced
overdense plasmas at surfaces the recoil energy distribution
appears much narrower. Comparing free lead clusters with lead
clusters embedded in large helium droplets, the charging
dynamics show distinct differences on the femtosecond time
scale. In the embedded case the maximum ionization enhancement
is reached earlier. 相似文献
13.
At the Prague Asterix Laser System Center (PALS) the Asterix iodine laser delivering up to 700 J/0.5 ns is used as a pump
source for X-ray laser experiments and applications. The prepulse technique was applied which is known to improve the neon-like
X-ray laser output at the J = 0-1 transition dramatically. Since Zn slab targets were used the operating wavelength was 21.2 nm. A prepulse having up
to 20 J precedes the main pulse by 10 ns. The main beam and the prepulse beam are focussed by two different optical systems
separately and their foci are superimposed at the target surface. By implementing a half-cavity set-up for double-pass amplification
using a Mo/Si multilayer mirror - which can be used for more than 100 shots - the X-ray laser output was more than 10 times
stronger than at the single pass in a 30 mm long plasma. Double-pass amplification was observed to be most efficient when
the pump pulse duration was at least 150 ps longer than the round trip time ( ≈ 260 ps) in the half-cavity. Under this fundamental
condition the X-ray laser reached saturation in the double-pass regime containing approx. 4 mJ energy which has been proved
to be enough for future applications. In this contribution, the X-ray laser features like divergence in two dimensions, the
beam quality (symmetry), the pointing angle and the integrated intensity giving an estimation of the output energy are investigated
over 110 shots. To characterize the stability of the X-ray laser the shot distribution, the mean value and the standard deviation
for these parameters are evaluated. For 18 shots in a series - what was achievable during one day - the corresponding values
are given, and a statistical analysis carrying out a chi-squared test characterize the Zn X-ray laser as a robust tool suitable
for applications. In the future it is planned to allocate X-ray laser beam time to external research groups.
Received 17 May 2002 / Received in final form 10 September 2002 Published online 6 November 2002
RID="a"
ID="a"e-mail: praeg@fzu.cz 相似文献
14.
K. Shigemori D. Ichinose T. Irifune K. Otani T. Shiota T. Sakaiya H. Azechi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):301-305
We present a novel scheme to measure sound velocity of
shock-compressed iron of geophysical interest. The sound velocity of
laser-irradiated iron foils was obtained with side-on X-ray radiograph
technique from measured rarefaction wave velocity of shocked iron. Iron
foils were irradiated with a two-stepped square laser pulse to reach Earth's
core condition by double compression. The experimental parameters of
temperature and pressure were very close to the Earth's core condition. 相似文献
15.
T. Mocek B. Rus M. Kozlová J. Polan P. Homer K. Jakubczak M. Stupka D. Snopek J. Nejdl M. H. Edwards D. S. Whittaker G. J. Tallents P. Mistry G. J. Pert N. Booth Z. Zhai M. Fajardo P. Zeitoun J. Chalupsky V. Hájková L. Juha 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):439-444
An overview of recent advances in applications of currently the most energetic X-ray laser at 21 nm is given. The unique parameters
of this half-cavity based X-ray laser such as record output energy of 10 mJ, highly symmetric beam, robustness and reproducibility,
have made it possible to carry out a number of multidisciplinary scientific projects featuring novel applications of intense
coherent X-ray radiation. Selected results obtained in these experiments are reviewed, including X-ray laser probing of dense
plasmas, measurements of transmission of focused soft X-ray radiation at intensities of up to 1012 W cm-2, measurements of infrared laser ablation rates of thin foils, and ablative microstructuring of solids. 相似文献
16.
S. Teuber T. Döppner T. Fennel J. Tiggesbäumker K.H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):59-63
The photoionization of metal clusters in intense femtosecond laser fields has been studied. In contrast to an experiment on
atoms, the interaction in this case leads to a very efficient and high charging of the particle where tens of electrons per
atom are ejected from the cluster. The recoil energy distribution of the atomic fragment ions was measured which in the case
of lead clusters exceeds 180 keV. Enhanced charging efficiency which we observed earlier for specific pulse conditions is
not reflected in the recoil energy spectra. Both the average and the maximum energies decrease with increasing laser pulse
width. This is in good agreement with molecular dynamics calculations.
Received 20 December 2000 相似文献
17.
M. Temporal S. Atzeni D. Batani M. Koenig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):509-511
The impedance mismatch effect in a two-layer (low density plastic foam, and solid aluminum, respectively) plane target compressed
by a laser driven shock wave is considered. In such targets the ablative pressure generated by absorption of laser light in
the foam layer is amplified when crossing the foam-aluminum interface. In this paper an analytical model is developed to evaluate
the shock pressure in the aluminum layer as a function of the density and thickness of the foam layer and of the laser parameters.
The model is in good agreement with previously published experimental results [A. Benuzzi et al., Phys. Plasmas 5, 2827 (1998)].
Received 20 January 2000 and Received in final form 16 May 2000 相似文献
18.
G. M. Petrov J. Davis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):629-639
The dynamics of clusters irradiated by a high-intensity ultrashort pulse
laser has been studied using a fully relativistic three-dimensional
Molecular Dynamics Model. A fast three-dimensional tree algorithm for
computing the electrostatic force has been developed and compared with the
conventional particle-particle method. The particle-particle method requires
computation time, which scales as O(Np
2), and it is faster for small
number of particles Np <103. In the opposite case of relatively large
ensemble of particles Np >103, the preferred method is the tree
algorithm whose computation time scales as O(Np log Np). The tree
algorithm has been benchmarked against the particle-particle method for
clusters composed of xenon and deuterium atoms and its accuracy and
computation time have been analyzed. The optimum free parameter of the tree
method has been determined to be θ≈0.5. We addressed the
effects of boundary conditions by studying the contribution of adjacent
clusters to the total electromagnetic force exerted on individual particles.
We found that the adjacent clusters play a minor role in the overall cluster
dynamics. 相似文献
19.
J. A. Pomarico D. I. Iriarte H. O. Di Rocco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):65-72
In this paper we analyze the variations in line intensities ratios due to a non-equilibrium situation and to optical depth
effects. A four level model is proposed and the two particular situations for the possible transitions are considered. Electron
density and temperature as well as the source thickness are used as independent parameters to find out in which way and extent
they modify the ratios of levels populations compared with the ideal case of an equilibrium state and optically thin source.
Accordingly with the ion of interest, electron temperatures ranging from I/20 to I/7 eV (I being the ionization energy), whereas electron densities in the interval from 1014 to 1020 cm-3 will be considered. These ranges are of special interest for diverse applications such as LIBS and measurement of transition
probabilities. Some results are presented for real ions and a new expression for the escape factor is also proposed for general
plasma conditions.
Received 12 June 2001 and Received in final form 24 October 2001 相似文献
20.
Progress in direct-drive inertial confinement fusion research at the
laboratory for laser energetics
R. L. McCrory D. D. Meyerhofer S. J. Loucks S. Skupsky R. Betti T. R. Boehly T. J.B. Collins R. S. Craxton J. A. Delettrez D. H. Edgell R. Epstein K. A. Fletcher C. Freeman J. A. Frenje V. Yu. Glebov V. N. Goncharov D. R. Harding I. V. Igumenshchev R. L. Keck J. D. Kilkenny J. P. Knauer C. K. Li J. Marciante J. A. Marozas F. J. Marshall A. V. Maximov P. W. McKenty S. F.B. Morse J. Myatt S. Padalino R. D. Petrasso P. B. Radha S. P. Regan T. C. Sangster F. H. Séguin W. Seka V. A. Smalyuk J. M. Soures C. Stoeckl B. Yaakobi J. D. Zuegel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):233-238
Direct-drive inertial confinement fusion (ICF) is
expected to demonstrate high gain on the National Ignition Facility (NIF) in
the next decade and is a leading candidate for inertial fusion energy
production. The demonstration of high areal densities in hydrodynamically
scaled cryogenic DT or D2 implosions with neutron yields that are a
significant fraction of the “clean” 1-D predictions will validate the
ignition-equivalent direct-drive target performance on the OMEGA laser at
the Laboratory for Laser Energetics (LLE). This paper highlights the
recent experimental and theoretical progress leading toward achieving this
validation in the next few years.
The NIF will initially be configured for X-ray drive and with no beams
placed at the target equator to provide a symmetric irradiation of a
direct-drive capsule. LLE is developing the “polar-direct-drive” (PDD)
approach that repoints beams toward the target equator. Initial 2-D
simulations have shown ignition. A unique “Saturn-like” plastic ring
around the equator refracts the laser light incident near the equator toward
the target, improving the drive uniformity.
LLE is currently constructing the multibeam, 2.6-kJ/beam, petawatt laser
system OMEGA EP. Integrated fast-ignition experiments, combining the OMEGA
EP and OMEGA Laser Systems, will begin in FY08. 相似文献