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1.
Effects of non-local thermodynamic equilibrium (non-LTE) condition on emission and hydrodynamics of typical inertial confinement
fusion (ICF) plasmas are studied. The average degree of ionization at high temperatures is seen to be much lower compared
to the values obtained from Thomas-Fermi scaling or Saha equation for high-Z element like gold. LTE and non-LTE predictions for emitted radiation from laser-driven gold foil are compared with the experimental
results and it is seen that non-LTE simulations show a marked improvement over LTE results. The effects of one group and multigroup,
LTE and non-LTE approximations of radiation transport on hydrodynamic parameters are studied for laser-driven aluminium and
gold foils. It is further seen that non-LTE and multigroup effects play an important role in predicting conversion efficiency
of laser light to X-rays. 相似文献
2.
Yu. K. Zemtsov A. Yu. Sechin A. N. Starostin A. G. Leonov A. A. Rudenko D. I. Chekhov 《Journal of Experimental and Theoretical Physics》1998,87(1):76-86
The purely thermal visible and infrared radiation emitted by a dense resonant medium (sodium vapor) heated nonuniformly to
temperatures of 600–1200 K was investigated experimentally for the first time under conditions where the photon mean free
path is comparable with the emission wavelength. The profile of the recorded spectra and the absolute luminescence intensities
in the different spectral ranges show good agreement with the results of a numerical simulation using a previously developed
theory of resonance radiation transport which assumes a Boltzmann spectral distribution of the resonant level population proportional
to exp(−ℏω/T). The self-reversed resonant sodium line exhibited strong asymmetry and it was shown that under certain conditions, the luminescence
spectrum of the medium may exhibit an additional broad peak on the far “red” limb of the resonance line. Calculations and
measurements demonstrated that the intensity of the thermal emission of sodium vapor at this red peak is several orders of
magnitude higher than that obtained from the standard theory of resonance radiation transport. This effect is arbitrarily
termed an infrared “ catastrophe.” It is noted that in a solar corona plasma and in gas-discharge lamps, the far red limbs
of the resonant lines may make a substantial contribution to the total luminescence intensity and in some cases, considerably
exceed the intensity of the photorecombination and bremsstrahlung continuum.
Zh. éksp. Teor. Fiz. 114, 135–154 (July 1998) 相似文献
3.
ICF内爆物理研究中,示踪元素X射线谱诊断方法是推测内爆压缩温度、 密度以及燃料混合状态的有效方法.针对其中的非平衡物理过程, 研制了非局域热动平衡(non-LTE)下一维谱线输运程序Alpha.程序以辐射流体计算给出的温度、 密度等量为输入条件,求解细致组态(DCA)模型下的原子动力学方程和辐射输运方程, 自洽给出谱线不透明度,和成像面上的X射线谱分布.利用该程序,模拟了神光Ⅱ装置上的掺Ar靶丸内爆示踪元素X射线谱诊断实验, 研究结果表明,谱线的自吸收效应影响发射的X射线谱的强度和形状, 谱线的宽度对自吸收效应的强弱也有影响.因此,在对X射线谱的数值模拟中应该考虑自吸收效应. 另外,与LTE近似下的发射谱的比较表明, LTE近似下,等离子体电离度大~1, 发射谱的形状与non-LTE的结果不同,且LTE近似下,谱线的强度比non-LTE的谱线强度大5-10倍, 采用LTE近似是不合适的. 相似文献
4.
The spatial field distribution is determined for the transition radiation generated by a particle passing through the apex
of a cone along its axis. Expressions for the angular distribution of the radiation intensity are obtained for apex angles
between 0 and π. Characteristics of transition radiation emitted into a “funnel” and a dihedral angle are compared. 相似文献
5.
H. Satz 《The European physical journal. Special topics》2008,155(1):167-175
Multihadron production in high energy collisions, from e+e-
annihilation to heavy ion interactions, shows remarkable thermal
behaviour, specified by a universal “Hagedorn” temperature.
We argue that this hadronic radiation is formed by tunneling
through the event horizon of colour confinement, i.e., that it
is the QCD counterpart of Hawking-Unruh radiation from black holes.
It is shown to be emitted at a universal temperature TH ≃
(σ/2 π)1/2, where σ denotes the string tension.
Since the event horizon does not allow information transfer,
the radiation is thermal “at birth”. 相似文献
6.
N. Mukunda 《Pramana》1998,51(5):643-649
The conventional separation of states of the quantised radiation field into “classical” and “nonclassical” types is expressed
in a dual operator form and then refined. This is based on new features of the normal ordering rule for passage from classical
to quantum dynamical variables. The cases of single and two-mode radiation fields are discussed 相似文献
7.
在间接驱动惯性约束聚变的黑腔中,辐射烧蚀的高Z等离子体的流体力学运动过程对激光注入黑腔的效率、辐射场均匀性和通过诊断口的黑腔辐射温度诊断都有显著影响。为研究诊断口在黑腔辐射场中的等离子体缩口过程,用激光产生X光辐射加热低Z泡沫填充的金黑腔诊断口,以激光辐照钛平面靶产生的2~5 keV高能段窄能区X光作为背光源,用X光分幅相机获得了源靶和小孔靶两种靶型的小孔等离子体运动过程图像,研究了X光烧蚀的小孔等离子体的流体力学运动过程,探索了定量测量小孔等离子体面密度的空间分布与时间演化过程的实验诊断方法,初步给出小孔等离子体的面密度。 相似文献
8.
The theory of X-ray radiation from relativistic channeled electrons at the Bragg angles—parametric X-ray radiation (PXR) during channeling (PXRC)—is developed while accounting for two quantum effects: the initial population of bound states of transverse motion and the transverse “form-factor” of channeled electrons. An experiment was conducted using a 255 MeV electron beam from a linac at the SAGA Light Source. We have identified a difference in the angular distributions of PXR and PXRC and obtained a fairly good agreement between the theoretical and experimental results. 相似文献
9.
O. V. Ovodova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》1997,85(2):257-263
A one-dimensional model of a helium atom in an intense field of a femtosecond electromagnetic pulse has been constructed using
the Hartree technique. “Exact” calculations have been compared to the approximations of “frozen” and “passive” electrons.
A nonmonotonic dependence of the single-electron ionization probability on the radiation intensity has been detected. Minima
in the ionization probability are due to multiphoton resonances between different atomic states due to the dynamic Stark effect.
We suggest that the ionization suppression is due to the interference stabilization in this case.
Zh. éksp. Teor. Fiz. 112, 470–482 (August 1997) 相似文献
10.
J.-J. Shin D. R. Ermer S. C. Langford J. T. Dickinson 《Applied Physics A: Materials Science & Processing》1996,64(1):7-17
Visible fluorescent “plumes” are readily produced when nominally transparent ionic materials are exposed to pulsed UV laser
irradiation. Over a wide range of laser fluences where plumes are observed, however, the photon and electron densities are
inadequate to support multiphoton ionization and inverse bremsstrahlung, which are often used to explain plasma production
and excitation of atomic spectral lines. We present evidence that the great majority of charged particles (electrons and positive
ions) comprising the plume at the onset of formation in defect-laden NaNO3 are emitted directly from the surface. A model is described wherein the required electron energy to excite and eventually
ionize neutral atoms is provided by electrostatic interactions in the expanding plume. The time evolution of the “overlap”
between the expanding charge cloud and thermally emitted neutrals accounts for the time evolution of the atomic line emissions
after the laser pulse.
Received: 15 August 1996/Accepted: 16 August 1996 相似文献
11.
D. V. Yanin A. V. Kostrov A. I. Smirnov M. E. Gushchin S. V. Korobkov A. V. Strikovskii V. I. Gundorin V. V. Nazarov M. V. Starodubtsev 《Technical Physics》2012,57(4):468-477
A method of resonant near-field microwave probing is developed for contactless diagnostics of a high-pressure plasma. The
efficiency of this method in measuring the parameters of the plasma of an rf capacitive discharge in argon under atmospheric
pressure is demonstrated. The experimental results are compared with the data obtained using the independent method, the microwave
radiation “cutoff,” and with theoretical estimates. 相似文献
12.
Harel Primack Reinhold Blümel 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):299-301
With respect to a “hot”, non-crystallized beam the synchrotron radiation of a cold crystallized beam is considerably modified.
We predict suppression of synchrotron radiation emitted by a crystallized beam in a storage ring. We also propose experiments
to detect this effect.
Received: 19 June 1998 / Revised version: 10 August 1998 相似文献
13.
间接驱动激光聚变过程中,黑腔内物质处于非局域热动平衡(non-LTE)状态,而且辐射传输具有非平衡、各向异性等特点。为了精确描述黑腔辐射场的演化及其与物质的相互作用,最新研制的激光聚变二维总体LARED集成程序,基于non-LTE的多群辐射输运建模,首次实现了激光黑腔靶实验的全过程数值模拟。数值结果表明,辐射输运计算较好地反映了黑腔辐射场均匀性变化,腔壁光斑区与非光斑区X光发射强度比与实验测量值接近,靶丸压缩形状与实验图像定性一致。 相似文献
14.
A.A. Andreev U. Teubner I.V. Kurnin E. Förster 《Applied physics. B, Lasers and optics》2000,70(4):505-515
Soft-X-radiation in the “water-window” region (23.3–43.6 ?) mainly from carbon laser plasmas generated by subpicosecond (700 fs)
0.248-μm laser pulses is studied as a function of angle of incidence and intensity (up to 1018 W/cm2) for p-polarized laser light. Furthermore, comparison is made between plasmas generated from massive and foil targets. Numerical
calculations are performed using a hydrocode coupled to X-ray line and continuum emission calculations including radiation
transport. The optimized conditions to achieve maximum water-window X-ray emissivity and, in particular, carbon Lyman-α line
emission are investigated. In addition, analytical scalings are presented. These theoretical results are essentially confirmed
by previous experiments. It is found that at optimized conditions, picosecond or subpicosecond laser plasma X-ray sources
with a power of the order of 1–10 GW in a spectral window of 1 ? could be developed.
Received: 6 August 1998 / Final version: 6 August 1999 / Published online: 30 November 1999 相似文献
15.
I. I. Atknin N. V. Marchenkov A. G. Kulikov A. E. Blagov M. V. Kovalchuk 《Journal of Experimental and Theoretical Physics》2020,130(1):7-13
An approach to the simulation of reciprocal space maps corresponding to the maps obtained experimentally by the triple crystal X-ray diffractometry (TXD) is proposed. A specific feature of the approach is the use of spectral angular distribution diagrams of X-ray radiation, which allows one to visualize the two-dimensional pattern of the spectral angular “composition” of an X-ray beam after its interaction with each element of the scheme and thus to take into account the contribution of the hardware function of the experimental setup. The algorithms developed allow calculations for a wide class of radiation sources (from an X‑ray tube with any material of the anode to a synchrotron radiation source) and X-ray optical elements (slits, X-ray mirrors of monochromators, and analyzers). The results of simulation are compared with the experimental data for dispersive diffraction geometry, which confirms the adequacy of the proposed approach and its applicability to the simulation of a diffraction pattern corresponding to a real experiment in the triple crystal scheme. 相似文献
16.
Th. Kröll T. Behrens R. Krücken V. Bildstein R. Gernhäuser P. Maierbeck I. Stefanescu O. Ivanov J. Van de Walle N. Warr P. A. Butler J. Cederkäll P. Delahaye L. M. Fraile G. Georgiev U. Köster T. Sieber D. Voulot F. Wenander P. E. Kent A. Ekström K.-H. Speidel J. Leske S. Schielke D. Habs R. Lutter P. Thirolf H. Scheit T. Davinson 《The European physical journal. Special topics》2007,150(1):127-129
We report on “safe” Coulomb excitation of neutron-rich 138,140,142Xe
nuclei.
The radioactive nuclei have been produced by ISOLDE at CERN and
post-accelerated
by the REX-ISOLDE facility. The γ-rays emitted by the decay of excited
states have been detected by the MINIBALL array. Recent results are
presented. 相似文献
17.
R. Thissen P. Lablanquie R.I. Hall M. Ukai K. Ito 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):335-342
Photoionization of rare gas clusters in the innervalence shell region has been investigated using threshold photoelectron
and photoion spectrometers and synchrotron radiation. Two classes of states are found to play an important role: (A) valence
states, correlated to dissociation limits involving an ion with a hole in its innervalence ns shell, (B) Rydberg states correlated to dissociation limits involving an ion with a hole in its outervalence np shell plus an excited neutral atom. In dimers, class A states are “bright”, that is, accessible by photoionization, and serve
as an entrance step to form the class B “dark” states; this character fades as the size of the cluster increases. In the dimer,
the “Mulliken” valence state is found to present a shallow potential well housing a few vibrational levels; it is predissociated by the
class B Rydberg states. During the predissociation a remarkable energy transfer process is observed from the excited ion that
loses its innershell electron to its neutral partner.
Received: 10 February 1998 / Revised: 17 July 1998 / Accepted: 31 July 1998 相似文献
18.
The hydrogen migration in metals under the action of ionizing and acoustic radiation is considered. The joint action of ionizing
and acoustic radiation is found to enhance the hydrogen migration in metals (“interference” effect). The hydrogen transport
mechanism is determined by the interaction of ionizing radiation with the hydrogen subsystem of a metal and a vibrodiffusion
effect. 相似文献
19.
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