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1.
Eight beams 0.35μm laser with pulse duration of about 1.0ns and energy of 260J per beam was injected into a cylindrical cavity to generate intense x-ray radiation on the “Shengguang Ⅱ“ high power laser facility.Gold foils with a thickness in the range of 0.09-0.52μm were attached on the diagnostic hole of the cavity and ablated by the intense x-ray radiation.The propagating radiation heat wave in the high-Z gold plasma was observed clearly.For comparison,we also simulated the experimental results. 相似文献
2.
Experimental observation of ionization and shock fronts in foam targets driven by thermal radiation
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The behaviours of ionization and shock propagation in
radiatively heated material is crucial for the understanding of
indirect drive inertial confinement fusion as well as some
astrophysics phenomena. In this work, radiation field with a peak
temperature of up to 155 eV was generated in a gold cavity heated by
four laser beams on the SG-II laser system and was used to irradiate
a plastic foam cylinder at one end. The radiatively ablated foam
cylinder was then backlighted side-on by x-ray from a
laser-irradiated Ti disk. By observing the transmission decrease due
to the shock compression of the foam cylinder, the trajectories of shock
front were measured, and from the onset of the intense thermal
emission from the side of the cylinder, the propagations of
the ionization front were also observed on the same shot. The
experimental measurements were compared to predictions of the
radiation hydrodynamics code Multi-1D and reasonable agreements were
found. 相似文献
3.
Experimental Scaling for Mass Ablation Rate in Planar Targets Irradiated by Smoothed 0.351μm Laser Beam
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YANGJia-Min DINGYao-Nan ZHANGBao-Han YANGGuo-Hong ZHENGZhi-Jian ZHANGWen-Hai HUXin WANGYao-Mei ZHANGJi-Yan LIJun 《中国物理快报》2003,20(6):877-880
Layered planar targets, consists of al and Au layers, were irradiated by smoothed 0.351-μm-high power laser with relatively large focus spot on Xingguang Ⅱ laser facility. The burn-through time of laser ablation of Al sample has been obtained by measuring the delay time of Au N-Band x-ray emission with respect to the Al K-Band x-ray emission. The scaling law of mass ablation rate with the laser flux has been obtained by only varying the laser energy on the target surface on different shots. The experimental scaling law is greatly different from the results of Key et al. [Phys. Fluids 23 (1983) 2011] and is in good agreement with the analytical model. 相似文献
4.
With the highly optimized embedded-atom-method(EAM)potential and electron-phonon coupling factor obtained from experimental data,the dynamics of the formation of warm dense gold and the nuclear response of gold foils upon intense laser excitation were investigated using two-temperature molecular dynamics simulations.Considering laser energy densities ranging from 0.18 to 1.17 MJ/kg,we provide a microscopic picture of the formation of warm dense gold.A threshold(0.19 MJ/kg)for the laser energy density was determined,identifying two different melting mechanisms.For an energy density below 0.19 MJ/kg,the melting of the foil is controlled by the propagation of melt fronts from external surfaces,which results in heterogeneous melting on the time scale of hundreds of picoseconds.For an energy density above 0.19 MJ/kg,homogeneous nucleation and growth of liquid regions inside the foil play the leading role,and homogeneous melting occurs with several picoseconds.Compared with previous simulations and experimental measurements,the evaluated different threshold value indicates that the improvement in the electron heat capacity for the two-temperature model by including the kinetic information of electrons may predict better laser-matter interactions under such extreme non-equilibrium conditions. 相似文献
5.
There are two physical phenomena in a strong laser intensity. One is the high-order harmonic emission; the other is x-ray emission from optical-field ionized plasmas. The experiment of conversion from high-order harmonics to x-ray emissions was given with a 105fs Ti:sapphire laser by adjusting laser intensities. The ingredient in plasma was investigated by the numerical simulations.Our experimental results suggested that the free electrons have detrimental effects on harmonic generation but are favourable for x-ray emission from optical-field ionized plasmas. If we want to obtain more intense harmonic signals as a coherent light source in the soft x-ray region, we must avoid the production of free electrons in plasmas. At the same time, if we want to observe x-rays for the development of high-repetition-rate table-top soft x-ray lasers, we should strip all atoms in the plasmas to a necessary ionized stage by the optical-field-ionization in the field of a high-intensity laser pulse. 相似文献
6.
Alternate oscillations of self-terminating and recombination lasers in univalent calcium and strontium ions
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The univalent calcium and strontium ions have been confirmed as ideal lasing substances both for self-terminating laser and recombination laser by theoretically analysing their energy level structures and lasing mechanisms. With the optimization of the excitation circuit and the improvement of the laser cavity as well as the laser discharge tube, thealternate laser oscillatlons of the two laser mechanisms were suceessfully realized by longitudinal pulsed discharge in mixture vapours of helium and univalent ions of calcium or strontium, respectively. The dependences of laser performance on working parameters, together with the characteristics of the photoelectric pulse waveforms were elementally studied and analysed. 相似文献
7.
X-Ray Radiation Characteristics of Nested-Wire Array Implosion in Sino-Russian Joint Z-pinch Experiments on Angara-5-1 总被引:3,自引:0,他引:3
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徐荣昆李正宏 宁佳敏郭存许泽平 杨建伦李林波夏广新 毕欣生丁宁刘强 顾元朝E.V.Grabovsky G.M.Oleynic S.L.Nedoseev V.V.Alexandrov K.N.Mitrofanov M.V.Zurin G.S.Volkov I.A.Porofeev I.N.Frolov V.P.Smirnov 《中国物理快报》2005,22(2):413-415
We report and discuss the results of x-ray radiation measurements in the Sino-Russian joint Z-Pinch experiments on Angara-5-1 facility with a load current of 2.5-3.6MA. The measurements were conducted by using an x-ray power meter (XRPM) and a time-resolved one-dimensional x-ray imaging system developed in China Academy of Engineering Physics. The experimental results indicate that an x-ray power-platform prior to a main peak and a less intensive sub-peak after the main peak in the waveform exist for the nested-wire array implosions, and the radiation process is relatively faster than that in the case of the single array. Laser shadowgraph of the imploding plasma suggests that the prior power-platform is a result of the collision of the inner-outer plasma layers. The faster radiation process of nested array implosion can be explained by analysing the corresponding result of the time-resolved one-dimensional imaging system, which demonstrates a better axial imploding uniformity and synchronization. In comparison with x-ray diode, the XRPM yields a higher height of x-ray power-platform due to its fiat energy response. The sub-peak after the main peak is proposed to be a result of the later-time additional implosion of plasma. 相似文献
8.
《中国物理 B》2015,(10)
Ultrashort multi-ke V x-ray pulses are generated by electron plasma produced by the irradiation of femtosecond pulses on metals. These sub-picosecond x-ray pulses have extended the field of x-ray spectroscopy into the femtosecond time domain. However, pulse-to-pulse instability and long data acquisition time restrict the application of ultrashort x-ray systems operating at low repetition rates. Here we report on the performance of a femtosecond laser plasma-induced hard x-ray source that operates at 1-k Hz repetition rate, and provides a flux of 2.0 × 1010 photons/s of Cu Kαradiation. Using this system for time-resolved x-ray diffraction experiments, we record in real time, the transient processes and structural changes induced by the interaction of 400-nm femtosecond pulse with the surface of a 200-nm thick Au(111) single crystal. 相似文献
9.
P. Xu Shining Zhu 《量子光学学报》2006,12(B08):85-85
An intense comb-shaped Raman spectra were obtained from a two-dimensional nonlinear x(2) photonic crystal - a hexagonally poled LiTaO3 crystal with lattice parameter 9 micros. The lowest Raman shift was down to 2 cm^-1 and the order of anti-stokes and stokes signals both achieved 11. The novel Raman spectra were mediated first by intense phonon-polariton fields, which were driven through the quasi-phase-matched coupling between the incident dual-beam both from an optical parametric oscillation laser, and further amplified greatly also by such quasi-phasematched nonlinear optical process. The dependence of the Raman spectra character on the wavelength and intensity of incident beams were studied in detail, which accordingly revealed information of the inelastic scattering and the elementary excitation in the nonlinear medium. These results on the other hand suggest technological importance for developing a novel Raman laser with the multi-wavelength output and a tunable frequency interval and for possible applications in quantum optics. 相似文献
10.
MinhuaJiang YuliaTian JianhuaJiang WanxiaHuang JiyangWang Xiao 《北京同步辐射装置》2001,(2):131-137,
Pure and neodymium-doped gadolinium calcium oxoborate crystals of high quality were grown by the Czochralski method.The orientation of crystal was precisely determined,and the samples for measurements were prepared.Through synchrotron x-ray topography and high-resolution x-ray diffractometry,the twin structure was discovered.Some properties such as the figure of merit value,and dielectric,piezoelectric,and elastic constants were meausured along with a discussion of the anisotropy of the laser properties. 相似文献
11.
《中国光学快报(英文版)》2015,(7)
<正>With the rapid development of ultrafast intense laser technologies,the interaction of intense laser radiation with matter has been a frontier for few decades.The International Conference on Multiphoton Processes(ICOMP).initiated in 1977,covers the latest advances in the field every three years.The special issue is based on the spirit of the 13th International Conference on Multi-Photon Processes,ICOMP13.which was held in Shanghai,organized by Shanghai 相似文献
12.
Characteristics of ultrafast K line hard x—ray source from femtosecond terawatt laser—produced plasma
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Theoretical studies and analytical scalings were carried out to find the optimized laser parameters and target conditions so that ultrashort hard x-ray pulses and high x-ray power could be achieved.The dependence of laser intensity and wavelength on the yield of K-shell x-ray emission was studied.We propose an optimal design for a foil target for producing high-yield hard x-ray pulses of customizing duration. 相似文献
13.
Displacement sensor based on the polarization mixture and the cavity tuning of the orthogonal polarized He-Ne laser 1.15μm is presented.The power tuning curves of He-Ne laser are irregular,and it is difficult to measure the change in cavity length.The distortion of the curves is caused by the higher relative excitation compared with the He-Ne laser at 633 nm.In view of its potential for the wider displacement measuring range,a new method of displacement sensing is developed.Experiments show that displacement measuring stability based on the method of the polarization mixture is better than that of the power tuning curves. The displacement sensor achieves the measuring range of 100 mm,resolution of 144 nm,and linearity of 7×10-6 . 相似文献
14.
MA Yan-Liang OUYANG Xiao-Ping ZHANG Jing-Wen ZHANG Zhong-Bing PAN Hong-Bo CHEN Liang LIU Lin-Yue 《中国物理C(英文版)》2010,34(3)
In this paper, properties on pulsed radiation detections of ZnO:Ga crystal grew by a magnetron sputtering method were studied. The time response to pulsed laser,pulsed hard X rays and single α particles, the energy response to pulsed hard X ray, the scintillation efficiency to γ rays, the response to pulsed proton, and the relations of the light intensity varied with the proton energy were measured and analyzed in detail. Results show that the ZnO:Ga crystal has potential applications in the regime of pulse radiation detection . 相似文献
15.
In this paper, properties on pulsed radiation detections of ZnO:Ga crystal grew by a magnetron sputtering method were studied. The time response to pulsed laser, pulsed hard X rays and single α particles, the energy response to pulsed hard X ray, the scintillation efficiency to γ rays, the response to pulsed proton, and the relations of the light intensity varied with the proton energy were measured and analyzed in detail. Results show that the ZnO:Ga crystal has potential applications in the regime of pulse radiation detection. 相似文献
16.
S. I. Yushchuk 《Technical Physics》1999,44(12):1454-1456
The layered structure of yttrium iron garnet films, ranging in thickness from 0.7 to 4.1 μm, grown epitaxially on single-crystal
gallium-gadolinium garnet substrates, was investigated by x-ray spectral microanalysis. The ferrite films were chemically
etched layer by layer in a mixture of orthophosphoric and sulfuric acids at T=353–423 K. It was established that the chemical composition of the films varies over the thickness because of the nonuniform
distribution of gadolinium, gallium, lead, and platinum ions; the film-substrate transitional layer and the surface layer
of the film differ most greatly with respect to the composition and magnetic properties. It was shown that the thickness of
the transitional layers and their negative effect on the magnetic characteristics of ferrite films decrease appreciably if
at the time of immersion of the substrate and pulling of epitaxial structure out of the fluxed solution the substrate holder
together with a special mixer rotate at a rate of 50 rpm and the pulling velocity is 20 cm/min.
Zh. Tekh. Fiz. 69, 62–64 (December 1999) 相似文献
17.
A tunable XUV monochromatic light source based on the time preserving grating selection of high-order harmonic generation
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We accomplish a laboratory facility for producing a femtosecond XUV coherent monochromatic radiation with a broad tunable spectral range of 20 eV-75 eV. It is based on spectral selected single-order harmonics from intense laser driven high harmonic generation in gas phase. The time preserving for the selected harmonic radiation is achieved by a Czerny-Turner type monochromator designed with a conical diffraction grating mount for minimizing the time broadening caused by grating diffraction and keeping a relatively high diffraction efficiency. Our measurement shows that the photon flux of the 23-order harmonic(H23) centered at 35.7 eV is 1×10~9 photons/s approximately with a resolving power E/?E ≈ 36.This source provides an ultrashort tunable monochromatic XUV beam for ultrafast studies of electronic and structural dynamics in a large variety of matters. 相似文献
18.
Radiation Temperature Scaling Law for Gold Hohlraum Heated with Lasers at 0.35 mm Wavelength
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We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ (SG- Ⅱ) laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J. The reradiated x-ray flux through the laser entrance hole was measured using a soft x-ray spectrometer. The measured peak radiation temperature was 170eV for the standard hohlraum and 150 eV for the 1.5-scaled one. We have derived the radiation temperature scaling law, in which the laser hohlraum coupling efficiency is included. With an appropriate coupling efficiency, the coincidences between experimental and scaling hohlraum radiation temperatures are rather good. 相似文献
19.
RF excited CO2 waveguide laser arrays with three different structures (one-dimension and two-dimension) are reported in this paper. The output character of far-field and near-field of those lasers have studies and the phase locking between the waveguide elements has discussed. The cavity length of waveguide laser array is 380 mm and the resonator is formed by placing a plane germanium coated gold mirror and a plane ZnSe output coupler. The laser is operated with filling static gas of He∶N2∶CO2∶Xe=3∶1∶1∶0.1 mixture at 1.06×104 Pa total pressure. High output power density is achieved and the output power is 30-w with an efficiency η=10%. The output power is limited by the maximum power of RF transmitter. 相似文献
20.
Effect of sheath potential on electromagnetic radiation emitted from the rear surface of a metallic foil target
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In ultra-intense laser--matter interactions, intense electric fields
formed at the rear surface of a foil target may have strong
influences on the motion of energetic electrons, and thereby affect
the electromagnetic emissions from the rear surface, usually ascribed
to transition radiation. Due to the electric fields, transition
radiation occurs twice and bremsstrahlung radiation also happens
because the electrons will cross the rear surface twice and have
large accelerations. In the optic region, transition radiation is
dominant. The radiation spectrum depends on the electric field only
when the electrons are monochromatic, and becomes independent of the
electric field when the electrons have a broadband momentum
distribution. Therefore, in an actual experiment, the electric field
at the rear surface of a foil could not be studied just with the
measurement of optic emissions. In the terahertz region, both
bremsstrahlung and transition radiations should be taken into
account, and the radiation power could be enhanced in comparison with
that without the inclusion of bremsstrahlung radiation. The frequency
at which the maximum terahertz radiation appears depends on the
electric field. 相似文献