共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
YU Xuecai YE Yutang WU Yunfeng XIE Kang & CHENG Lin College of Opto-Electronic Information University of Electronic Science Technology of China Chengdu China 《中国科学G辑(英文版)》2005,48(5):521-528
It has been a long history to study Bose-Einstein condensation (BEC) of weakly in-teracting Bose gas, and several theoretical models have been developed to research uni-form and weakly interacting Bose gas. Ref. [1] summarized all of these models and the corresponding results, which gave a derivation of critical temperature from ideal case 1/30Tc c n,?T = α (1) with a wide spread of parameter c from 0.7 to 2.33, where α is the scattering length of s wave and n is atom number density. Due… 相似文献
3.
L. Giuggioli Z. Kalay V. M. Kenkre 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):341-348
We study the transient dynamics of single species reaction diffusion systems whose reaction terms f(u) vary nonlinearly near
u ≈ 0, specifically as f(u) ≈ u2 and f(u) ≈ u3. We consider three cases, calculate
their traveling wave fronts and speeds analytically and solve the equations numerically with different initial conditions to study the approach to the asymptotic front shape
and speed. Observed time evolution is found to be
quite sensitive to initial conditions and to display in some cases nonmonotonic behavior, ascribable to the disparity in time
scales between the evolution of the front interior and the front tail. 相似文献
4.
W. Holzer A. Penzkofer T. Pertsch N. Danz A. Bräuer E.B. Kley H. Tillmann C. Bader H.-H. Hörhold 《Applied physics. B, Lasers and optics》2002,74(4-5):333-342
Wave-guided thin-film distributed-feedback (DFB) polymer lasers are fabricated by spin coating a PPV-derived semiconducting
polymer, thianthrene-DOO-PPV, onto oxidised silicon wafers with corrugated second-order periodic gratings. The gratings are
written by reactive ion beam etching. Laser action is achieved by transverse pumping with picosecond laser pulses (wavelength
347.15 nm, duration 35 ps). The DFB-laser surface emission and edge emission are analysed. Outside the grating region the
polymer film is used for comparative wave-guided travelling wave laser (amplified spontaneous emission (ASE)) studies. The
pump pulse threshold energy density for wave-guided DFB-laser action (4–9 μJ cm-2) is found to be approximately a factor of two lower than the threshold for wave-guided travelling wave laser action. The
spectral width of the DFB laser (down to ΔλDFB≈0.07 nm) is considerably narrower than that of the travelling wave laser (ΔλTWL≈14 nm). The DFB-laser emission is highly linearly polarised transverse to the grating axis (TE mode). Only at high pump pulse
energy densities does an additional weak TM mode build up. The surface-emitted DFB-laser radiation has a low divergence along
the grating direction. For both the DFB lasers and the travelling wave lasers, gain saturation occurs at high excitation energy
densities.
Received: 7 January 2002 / Revised version: 15 February 2002 / Published online: 14 March 2002 相似文献
5.
Rault J Marchal J Judeinstein P Albouy PA 《The European physical journal. E, Soft matter》2006,21(3):243-261
Stress-induced crystallisation (SIC) and stress-induced melting (SIM) in natural rubbers (NR), unfilled and filled with carbon
black (CB) have been studied by 2H-NMR measurements. Various materials have been swollen with small amount (< 2%) of deuterated alkane chains. The orientation
of the amorphous chains, then the local deformation of the amorphous chains during deformation cycles and during stress relaxation,
permits to clarify the SIC and SIM processes during hardening and recovery. By mechanical, WAXS and NMR measurements one determines
the same critical draw ratio for appearance λA and disappearance λE of the crystallites. It is demonstrated that the hysteresis observed by the different techniques (stress σ, crystallinity
χ, NMR splitting Δν) are due to the supercooling effect ( λA > λE, at constant temperature). During hardening at constant strain rate it is found that the local draw ratio remains constant
and equal to λA, whereas the crystallinity increases linearly with the macroscopic draw ratio λ. The hardening σ ∼ (λ - λA)2 is then interpreted as a reinforcement effect due to the crystallites, which act as new crosslinks. This confirms the prediction
of Flory. In filled rubber the same effects are observed, and the stress amplification factor is determined as a function
of the CB content. It is found that the fillers act as nucleation centres for the NR crystallites. The reinforcement of such
materials is due principally to this nucleation effect and to the presence of a super network formed by both the NR crystallites
and the CB fillers. 相似文献
6.
We describe a laser system that readily provides radiation tunable from 2 μm in the infra-red to 35 nm in the extreme ultraviolet
spectral range. The broad spectral range is covered through a range of non-linear processes such as Raman shifting and high-order
harmonic generation. Pulses with duration of tens of picoseconds are obtained. The relative bandwidth of the radiation is
δλ/λ=10-4, comparable with what can be achieved by using high-resolution monochromators at state-of-the-art synchrotron beamlines.
We discuss different methods for characterising the radiation in this wide wavelength regime. We also discuss the capabilities
of the system from the measured parameters.
Received: 12 December 2000 / Revised version: 8 March 2001 / Published online: 27 April 2001 相似文献
7.
A. Bolshakova I. Boyko G. Chelkov D. Dedovitch A. Elagin M. Gostkin S. Grishin A. Guskov Z. Kroumchtein Yu. Nefedov K. Nikolaev A. Zhemchugov F. Dydak J. Wotschack A. De Min V. Ammosov V. Gapienko V. Koreshev A. Semak Yu. Sviridov E. Usenko V. Zaets 《The European Physical Journal C - Particles and Fields》2009,62(2):293-317
We report on double-differential inclusive cross-sections of the production of secondary protons, deuterons, and charged pions
and kaons, in the interactions with a 5% λ
abs thick stationary beryllium target, of a +8.9 GeV/c proton and pion beam, and a −8.0 GeV/c pion beam. Results are given for secondary particles with production angles 20○<θ<125○.
On leave of absence at Ecole Polytechnique Fédérale, Lausanne, Switzerland. 相似文献
8.
C. de Lisio C. Altucci R. Bruzzese F. De Filippo S. Solimeno M. Bellini P. Foggi 《Applied physics. B, Lasers and optics》1997,64(3):323-330
We report the realization of a vacuum-ultraviolet radiation source based on high-order harmonic generation in noble-gas samples,
operating at high repetition rate. In particular, we observed up to the 13th harmonic (λ=61 nm) of the fundamental frequency
of a short pulse, high repetition rate titanium–sapphire laser after its interaction with a Xe gas jet. The effects of the
propagation of the fundamental and harmonic beams through an ionized medium are studied by analysing the spectral profile
of the 9th and 7th harmonics. Finally, we report a study of the dependence of the harmonic conversion efficiency on relative
position of the focus and the gas target.
Received: 29 March 1996/Revised version: 25 July 1996 相似文献
9.
M. Uebernickel C. Fiebig G. Blume K. Paschke B. Eppich R. Güther G. Erbert 《Applied physics. B, Lasers and optics》2008,93(4):823-827
Continuous wave power of more than 400 mW at 488 nm has been generated by frequency doubling of 2.45 W at 976 nm obtained
from a distributed Bragg reflector tapered diode laser. This results in a wavelength conversion efficiency of 16.5% and an
electrical-to-optical efficiency of more than 4.5%. We used a 50 mm long periodically poled MgO:LiNbO3 bulk crystal in single-pass configuration for the second harmonic generation. This is to the author’s knowledge the highest
output power and the highest wavelength conversion efficiency at 488 nm generated by a monolithic semiconductor laser device
in single pass configuration with a bulk crystal. A deviation from the quadratic dependency of the frequency doubling is explained
by the decrease of the beam quality of the fundamental wave. 相似文献
10.
We have theoretically and experimentally investigated the focusing properties of a detuned pulsed standing wave onto a beam
of neutral atoms. In close analogy to the continuous-wave situation the dipole force leads to a periodic focusing of atoms
with a period of λ/2, provided an adiabatic condition is fulfilled. Pulsed laser light is conveniently converted to short
wavelengths and hence offers advantages in the application of atom lithography with elements of technological interest having
blue or UV resonance lines.
Received: 6 October 1999 / Revised version: 3 February 2000 / Published online: 5 April 2000 相似文献
11.
Using a scaling approach we consider a 2D comb copolymer brush under bending deformations. We show that the rectilinear brush
is locally stable and can be characterized by a persistence length λ increasing with the molecular weight of grafting side
chains as λ ∼ M3. A bending instability due to redistribution of the side chains appears in the non-linear regime where bending is strong.
Arguments are presented that the brush conformations consist of alternating rectilinear and bent sections corresponding to
the different free-energy minima. 相似文献
12.
We have examined a number of candidates for the minimum-surface-energy arrangement of two-dimensional clusters composed of
N bubbles of area 1 and N bubbles of area λ ( λ≤1). These include hexagonal bubbles sorted into two monodisperse honeycomb tilings, and various mixed
periodic tilings with at most four bubbles per unit cell. We identify, as a function of λ, the minimal configuration for N → ∞. For finite N, the energy of the external (i.e., cluster-gas) boundary and that of the interface between honeycombs in “phase-separated” clusters have to be taken into account.
We estimate these contributions and find the lowest total energy configuration for each pair (N,λ). As λ is varied, this alternates between a circular cluster of one of the mixed tilings, and “partial wetting” of the
monodisperse honeycomb of bubble area 1 by the monodisperse honeycomb of bubble area λ.
Received 1 August 2002
RID="a"
ID="a"e-mail: paulo@ist.utl.pt 相似文献
13.
L. G. Moyano A. P. Majtey C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):493-500
We introduce, and numerically study, a system of N symplectically and globally coupled
standard maps localized in a d=1 lattice array. The global coupling is modulated
through a factor r-α, being
r the distance between maps. Thus, interactions are long-range (nonintegrable) when
0≤α≤1, and short-range (integrable) when α>1.
We verify that the largest Lyapunov exponent λM scales as λM ∝
N-κ(α), where κ(α) is positive when interactions are
long-range, yielding weak chaos in the thermodynamic
limit N↦∞ (hence λM→0). In the short-range case,
κ(α) appears to vanish,
and the behaviour corresponds to strong chaos. We show that, for certain
values of the control parameters of the system, long-lasting metastable states
can be present. Their duration tc scales as tc ∝Nβ(α),
where β(α) appears to be numerically in agreement with the following
behavior: β>0 for 0 ≤α< 1, and zero for α≥1.
These results are consistent with features typically found in nonextensive statistical mechanics.
Moreover, they exhibit strong similarity between the present
discrete-time system, and the α-XY Hamiltonian ferromagnetic model. 相似文献
14.
C.M. Horowitz E.V. Albano 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):563-569
The relationship between a microscopic parameter p, that is related to the probability of choosing a mechanism of deposition, and the stochastic equation for the interface's
evolution is studied for two different models. It is found that in one model, that is similar to ballistic deposition, the
corresponding stochastic equation can be represented by a Kardar-Parisi-Zhang (KPZ) equation where both λ and ν depend on
p in the following way: ν(p) = νp and λ(p) = λp
3/2. Furthermore, in the other studied model, which is similar to random deposition with relaxation, the stochastic equation
can be represented by an Edwards-Wilkinson (EW) equation where ν depends on p according to ν(p) = νp
2. It is expected that these results will help to find a framework for the development of stochastic equations starting from
microscopic details of growth models.
Received 26 August 2002 / Received in final form 20 November 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: ealbano@inifta.unlp.edu.ar 相似文献
15.
Etienne Shaffer Amr S. Helmy Dominique Drouin Jan J. Dubowski 《Applied Physics A: Materials Science & Processing》2008,93(4):869-874
We have investigated ArF (λ=193 nm) excimer laser-induced crystallization of amorphous CdSe semiconductor thin films. The crystallization has been monitored
by a related photoluminescence emission in the free-exciton and defect-band transition regions. For different irradiation
conditions, we have observed formation of nanorods, up to 2 μm long, as well as the formation of arrays of CdSe nanobeads
with a narrow size distribution and characteristic dimensions corresponding to λ/2 and λ/8. The successful crystallization has also been confirmed by confocal Raman spectroscopy. 相似文献
16.
L. R. Nie D. C. Mei 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):475-481
The properties of the underdamped Josephson junction subjected to
colored noises were investigated with large and small phase
difference (φ). For the case of the large φ, we found
numerically that: (i) the probability distribution function of
φ exhibits monostability → bistability → monostability
transitions as the autocorrelation rate (λ) of a colored
noise increases; (ii) in the bistability region the multiplicative
noise drives the phase difference to turn over periodically; (iii)
the slope K of the linear response of the junction potential
difference (〈V 〉) can be somewhat reduced by means of tuning an
optimal λ; (iv) the amplitude of φ in response to
external sinusoidal signals changes with λ. For the case of
small φ, after deriving the analytical expressions of the
potential difference amplitude (〈V 〉max) and the K in the
presence of a dichotomous noise, we found nonmonotonic behavior of
〈V 〉max and the slope K as a function of λ. 相似文献
17.
Igor Loutsenko Oksana Yermolayeva Michel Zinsmeister 《Journal of statistical physics》2011,145(4):919-931
We introduce a competitive model of Laplacian growth in both stochastic and deterministic versions. This defines two different
aggregation laws with probabilities λ and 1−λ. The parameter λ varying from 0 to 1 is used to weight a ratio between the inner and outer harmonic measures that leads to a competition between
the Eden-like process and the DLA solved with site-sticking conditions. We perform numerical and qualitative analysis of the
competitive growth. 相似文献
18.
Ito S. Ishikawa H. Miura T. Takasago K. Endo A. Torizuka K. 《Applied physics. B, Lasers and optics》2003,76(5):497-503
We present a 7-TW Ti:sapphire laser system operating at 50 Hz for laser Compton femtosecond X-ray generation. This laser system
delivers 8.4 W of average output power at a repetition rate of 50 Hz with a pulse width of 24 fs. It demonstrates successful
management using a dynamically stable resonator in the regenerative amplifier and compensation for thermal lensing by a convex
mirror in a ring-type four-pass power amplifier. We also present the results of closed-loop corrections for distorted wavefronts
of amplified and compressed laser pulses, using an adaptive optical system consisting of a Shack–Hartmann-type wavefront sensor
and a deformable mirror. This closed-loop correction results in dramatic improvements, reducing wavefront distortions below
0.05 λ rms.
Received: 31 October 2002 / Revised version: 3 March 2003 / Published online: 5 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/61-3349, E-mail: ito@festa.or.jp 相似文献
19.
H. Shu S.-Z. Fu X.-G. Huang M.-X. Ma J. Wu J.-J. Ye J.-H. He Y. Gu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):367-370
Using the ninth laser beam (converted to 2ω) of
“Shenguang-II” laser facility and the beam smoothing technology of
lens-array [Appl. Opt. 25, 377 (1986); Phys. Plasmas. 9, 3201 (1995)],
a shock wave with 700 μm (the root-mean-square of
shock breakout time (RMS) RMS ≈ 6.32 ps) flat top was created. An Al-Al
four-step target was designed to do research on shock wave stability in an
Al target. And the shock stability experiment with the Al-Al four-step
target indicated that the shock wave steadily propagated in the Al target of
thickness of about 20–45 μm under the power density of ~ 1.0×1014 W/cm2. 相似文献
20.
M. Kubkowska P. Gasior M. Rosinski J. Wolowski M. J. Sadowski K. Malinowski E. Skladnik-Sadowska 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):463-466
This paper describes results of spectroscopic investigation of laser-produced tungsten plasma. The laser intensity on the
target surface reached up to 30 GW/cm2 depending on the focusing conditions. Optical spectra emitted from plasma plumes which were formed under vacuum conditions
in front of the tungsten target due to the interaction of Nd-YAG laser pulses (1.06 μm, 0.5 J), were characterised by means
of an optical spectrometer (λ/Δλ= 900) in the wavelength range from 300 to 1100 nm. The spectra were recorded automatically
with the use of a CCD detector with exposition time varied from 100 ns to 50 ms. On the basis of WI and WII lines it was possible
to estimate electron temperature and electron density which corresponded to the expansion phase of the plasma. Te and Ne were measured as 1.1 eV and 8×1016 cm-3, respectively. The spectra collected by the ion energy analyser showed that the plasma included tungsten ions up to 6+ ion
charge. Signals from the ion collector allowed to estimate the average value of ion energy of tungsten as 4.6 keV. Basing
on this value the electron temperature corresponding to the initial stage of the plasma formation was estimated to be about
320 eV. Optical microscope investigation showed that laser irradiation caused structural changes on the surface of the target. 相似文献