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Now showing items 1 - 16 of 13313

  • A new isomeric state in Pa-218

    Zhang, M. M.   Yang, H. B.   Gan, Z. G.   Zhang, Z. Y.   Huang, M. H.   Ma, L.   Yang, C. L.   Yuan, C. X.   Wang, Y. S.   Tian, Y. L.   Zhou, H. B.   Huang, S.   He, X. T.   Wang, S. Y.   Xu, W. Z.   Li, H. W.   Xu, X. X.   Wang, J. G.   Yang, H. R.   Duan, L. M.   Yang, W. Q.   Zhou, S. G.   Ren, Z. Z.   Zhou, X. H.   Xu, H. S.   Voinov, A. A.   Tsyganov, Yu S.   Polyakov, A. N.   Shumeiko, M., V  

    The decay of Pa-218 was investigated by means of alpha and gamma spectroscopy. The nucleus was produced in the fusion reaction Ar-40+W-182 and separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure). The known alpha decays of Pa-218 were measured with improved precision and newly assigned to be originating from the ground state, which clarified the ambiguities in their previous assignments. In addition, a new isomeric state in Pa-218 decaying with alpha-particle energies of 9691(15) keV, 9595(21) keV and a half-life of 135(-32)(+62) mu s was identified. The spins and parities of the involved states were tentatively assigned on the basis of the systematic alpha-decay properties of the odd-proton N =3D 127 isotones and shell model calculations. (C) 2019 The Authors. Published by Elsevier B.V.
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  • Coherent synchrotron emission in transmission with double foil target

    Xu, X. R.   Qiao, B.   Chang, H. X.   Zhang, Y. X.   Zhang, H.   Zhong, C. L.   Zhou, C. T.   Zhu, S. P.   He, X. T.  

    Generation of intense single attosecond pulses from coherent synchrotron emission (CSE), in the transmitted direction of the laser-irradiated double foil targets, has been investigated theoretically and numerically. Unlike conventional CSE in the single foil target case, here the dense electron nanobunch is formed in the vacuum gap between two foils, which is composed of the electrons blown out from the first ultrathin foil. Owing to the existence of the vacuum gap, the electron nanobunch can be accelerated to more energy. In addition, more laser energy can penetrate through the nanobunch and get reflected from the second foil. These reflected lasers and electron nanobunches interact with each other and results in enhanced CSE and consequently, the generation of intense attosecond pulses. Particle-in-cell simulations show that a single attosecond pulse with duration of 18 as, photon energy >0.16 keV and peak intensity of 1.7 x 10(20) W/cm(2) can be obtained from the double-foil targets irradiated by a laser at intensity of 7.7 x 10(21) W/cm(2).
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    Yang, Z. X.   Sun, J. Y.   Ran, G. M.   He, X. T.  

    In this note, Foppl-Hencky membrane equation in the case of axisymmetric deformation was derived, and its power series solution was presented by using the displacement-based solution method. The result shows that both the displacement-based solution method and the stress-based solution method are effective for the solution to Foppl-Hencky equation. But in comparison with the latter, the former makes the solving process some more concise. In addition, some issues concerned were also discussed.
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  • Enhanced betatron radiation in strongly magnetized plasma

    Pan, K. Q.   Zheng, C. Y.   Cao, L. H.   Liu, Z. J.   He, X. T.  

    Betatron radiation in strongly magnetized plasma is investigated by two dimensional (2D) particle-in-cell (PIC) simulations. The results show that the betatron radiation in magnetized plasmas is strongly enhanced and is more collimated compared to that in unmagnetized plasma. Single particle model analysis shows that the frequency and the amplitude of the electrons's betatron oscillation are strongly influenced by the axial external magnetic field and the axial self-generated magnetic field. And the 2D PIC simulation shows that the axial magnetic field is actually induced by the external magnetic field and tends to increase the betatron frequency. By disturbing the perturbation of the plasma density in the laser-produced channel, the hosing instability is also suppressed, which results in a better angular distribution and a better symmetry of the betatron radiation. Published by AIP Publishing.
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  • Excitation of nonlinear ion acoustic waves in CH plasmas

    Feng, Q. S.   Zheng, C. Y.   Liu, Z. J.   Xiao, C. Z.   Wang, Q.   He, X. T.  

    Excitation of nonlinear ion acoustic wave (IAW) by an external electric field is demonstrated by Vlasov simulation. The frequency calculated by the dispersion relation with no damping is verified much closer to the resonance frequency of the small-amplitude nonlinear IAW than that calculated by the linear dispersion relation. When the wave number k lambda(De) increases, the linear Landau damping of the fast mode (its phase velocity is greater than any ion's thermal velocity) increases obviously in the region of T-i/T-e < 0.2 in which the fast mode is weakly damped mode. As a result, the deviation between the frequency calculated by the linear dispersion relation and that by the dispersion relation with no damping becomes larger with k lambda(De) increasing. When k lambda(De) is not large, such as k lambda(De) = 0.1, 0.3, 0.5, the nonlinear IAW can be excited by the driver with the linear frequency of the modes. However, when k lambda(De) is large, such as k lambda(De) = 0.7, the linear frequency cannot be applied to exciting the nonlinear IAW, while the frequency calculated by the dispersion relation with no damping can be applied to exciting the nonlinear IAW. Published by AIP Publishing.
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  • The updated advancements of inertial confinement fusion program in China

    He, X. T.  

    The recent achievements of ICF research in China are reviewed. The constructions of laser facilities of SG-III and SG-IIUP are completed in this year and the full energy output operation will be in 2014. The target physics studies involving numerical simulations of a new ignition scheme, which is proposed to enhance implosion velocity and suppress hydrodynamic instability and distortion at interface between hot spot and main fuel, and experimental results (a few selected examples) are presented.
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  • A spherical shell target scheme for laser-driven neutron sources

    He, Min-Qing   Cai, Hong-Bo   Zhang, Hua   Dong, Quan-Li   Zhou, Cang-Tao   Wu, Si-Zhong   Sheng, Zheng-Ming   Cao, Li-Hua   Zheng, Chun-Yang   Wu, Jun-Feng   Chen, Mo   Pei, Wen-Bing   Zhu, Shao-Ping   He, X. T.  

    A scheme for neutron production is investigated in which an ultra-intense laser is irradiated into a two-layer (deuterium and aurum) spherical shell target through the cone shaped entrance hole. It is found that the energy conversion efficiency from laser to target can reach as high as 71%, and deuterium ions are heated to a maximum energy of several MeV from the inner layer surface. These ions are accelerated towards the center of the cavity and accumulated finally with a high density up to tens of critical density in several picoseconds. Two different mechanisms account for the efficient yield of the neutrons in the cavity: (1) At the early stage, the neutrons are generated by the high energy deuterium ions based on the "beam-target" approach. (2) At the later stage, the neutrons are generated by the thermonuclear fusion when the most of the deuterium ions reach equilibrium in the cavity. It is also found that a large number of deuterium ions accelerated inward can pass through the target center and the outer Au layer and finally stopped in the CD2 layer. This also causes efficient yield of neutrons inside the CD2 layer due to "beam-target" approach. A postprocessor has been designed to evaluate the neutron yield and the neutron spectrum is obtained. (C) 2015 AIP Publishing LLC.
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  • A hybrid-drive nonisobaric-ignition scheme for inertial confinement fusion

    He, X. T.   Li, J. W.   Fan, Z. F.   Wang, L. F.   Liu, J.   Lan, K.   Wu, J. F.   Ye, W. H.  

    A new hybrid-drive ( HD) nonisobaric ignition scheme of inertial confinement fusion ( ICF) is proposed, in which a HD pressure to drive implosion dynamics increases via increasing density rather than temperature in the conventional indirect drive ( ID) and direct drive ( DD) approaches. In this HD ( combination of ID and DD) scheme, an assembled target of a spherical hohlraum and a layered deuterium-tritium capsule inside is used. The ID lasers first drive the shock to perform a spherical symmetry implosion and produce a large-scale corona plasma. Then, the DD lasers, whose critical surface in ID corona plasma is far from the radiation ablation front, drive a supersonic electron thermal wave, which slows down to a high-pressure electron compression wave, like a snowplow, piling up the corona plasma into high density and forming a HD pressurized plateau with a large width. The HD pressure is several times the conventional ID and DD ablation pressure and launches an enhanced precursor shock and a continuous compression wave, which give rise to the HD capsule implosion dynamics in a large implosion velocity. The hydrodynamic instabilities at imploding capsule interfaces are suppressed, and the continuous HD compression wave provides main pdV work large enough to hotspot, resulting in the HD nonisobaric ignition. The ignition condition and target design based on this scheme are given theoretically and by numerical simulations. It shows that the novel scheme can significantly suppress implosion asymmetry and hydrodynamic instabilities of current isobaric hotspot ignition design, and a high-gain ICF is promising. Published by AIP Publishing.
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  • A hybrid-drive nonisobaric-ignition scheme for inertial confinement fusion

    He, X. T.   Li, J. W.   Fan, Z. F.   Wang, L. F.   Liu, J.   Lan, K.   Wu, J. F.   Ye, W. H.  

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  • A Review of Equation-of-State Models for Inertial Confinement Fusion Materials

    Gaffney, J. A.   Hu, S. X.   Arnault, P.   Becker, A.   Benedict, L. X.   Boehly, T. R.   Celliers, P. M.   Ceperley, D. M.   Certik, O.   Clerouin, J.   Collins, G. W.   Collins, L. A.   Danel, J. -F.   Desbiens, N.   Dharma-wardana, M. W. C.   Ding, Y. H.   Fernandez-Panella, A.   Gregor, M. C.   Grabowski, P. E.   Hamel, S.   Hansen, S. B.   Harbour, L.   He, X. T.   Johnson, D. D.   Kang, W.   Karasiev, V. V.   Kazandjian, L.   Knudson, M. D.   Ogitsu, T.   Pierleoni, C.   Piron, R.   Redmer, R.   Robert, G.   Saumon, D.   Shamp, A.   Sjostrom, T.   Smirnov, A. V.   Starrett, C. E.   Sterne, P. A.   Wardlow, A.   Whitley, H. D.   Wilson, B.   Zhang, P.   Zurek, E.  

    Material equation-of-state (EOS) models, generally providing the pressure and internal energy for a given density and temperature, are required to close the equations of hydrodynamics. As a result they are an essential piece of physics used to simulate inertial confinement fusion (ICF) implosions. Historically, EOS models based on different physical/chemical pictures of matter have been developed for ICF relevant materials such as the deuterium (D-2) or deuterium-tritium (DT) fuel, as well as candidate ablator materials such as polystyrene (CH), glow-discharge polymer (GDP), beryllium (Be), carbon (C), and boron carbide (B4C). The accuracy of these EOS models can directly affect the reliability of ICF target design and understanding, as shock timing and material compressibility are essentially determined by what EOS models are used in ICF simulations. Systematic comparisons of current EOS models, benchmarking with experiments, not only help us to understand what the model differences are and why they occur, but also to identify the state-of-the-art EOS models for ICF target designers to use. For this purpose, the first Equation-of-State Workshop, supported by the US Department of Energy's ICF program, was held at the Laboratory for Laser Energetics (LLE), University of Rochester on 31 May-2nd June, 2017. This paper presents a detailed review on the findings from this workshop: (1) 5-10% model-model variations exist throughout the relevant parameter space, and can be much larger in regions where ionization and dissociation are occurring, (2) the D-2 EOS is particularly uncertain, with no single model able to match the available experimental data, and this drives similar uncertainties in the CH EOS, and ( 3) new experimental capabilities such as Hugoniot measurements around 100 Mbar and high-quality temperature measurements are essential to reducing EOS uncertainty.
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  • Advances in the national inertial fusion program of China

    He, X. T.   Zhang, W. Y.  

    The planned inertial confinement fusion (ICF) ignition in China in around 2020 is to be accomplished in three steps. The first is carrying out target physics experiments in the existing laser facilities SG-II, SG-IIIP and SG-IIU (operating in 2012) of output energy 3-24 kJ at 3 omega. Results have been obtained for better understanding the implosion dynamics and radiation transport. Recent studies include efficiency of radiation generation, hydrodynamic instabilities, shock waves in cryogenic targets, opacity measurements using kJ lasers, etc. Hydrodynamic codes (the LARED series) have been developed and experimentally verified with over 5000 shots, and are applied to investigating target physics and ignition target design. For fast ignition, a large number of experiments and numerical simulations have led to improved understanding relevant to target design, hot electron transport, collimation by the spontaneous magnetic fields in overdense plasmas, etc. In addition to the SG-II, SG-IIU and SG-IIIP, the SG-III laser facility with energy of 200-400 kJ at 3 omega shall operate in 2014 and be used for advanced target physics research. In the last step, the 1.5 MJ SG-IV laser facility still under design will be used to investigate ignition and burning.
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  • Gamma-ray source through inverse Compton scattering in a thermal hohlraum

    Ping, Y. L.   He, X. T.   Zhang, H.   Qiao, B.   Cai, H. B.   Chen, S. Y.  

    A new inverse Compton scattering scheme for production of high-energy Gamma-ray sources is proposed in which a Giga-electronvolt (GeV) electron beam is injected into a thermal hohlraum. It is found that by increasing the hohlraum background temperature, the scattered photons experience kinematic pileup, resulting in more monochromatic spectrum and smaller scattering angle. When a relativistic electron beam with energy 1 GeV and charge 10nC is injected into a 0.5 keV hohlraum, 80% of the scattered photons have energy above 0.5 GeV.
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  • Brilliant GeV gamma-ray flash from inverse Compton scattering in the QED regime

    Gong, Z.   Hu, R. H.   Lu, H. Y.   Yu, J. Q.   Wang, D. H.   Fu, E. G.   Chen, C. E.   He, X. T.   Yan, X. Q.  

    An all-optical scheme is proposed for studying laser plasma based incoherent photon emission from inverse Compton scattering in the quantum electrodynamic regime. A theoretical model is presented to explain the coupling effects among radiation reaction trapping, the self-generated magnetic field and the spiral attractor in phase space, which guarantees the transfer of energy and angular momentum from electromagnetic fields to particles. Taking advantage of a prospective similar to 10(23) W cm(-2) laser facility, 3D particle-in-cell simulations show a gamma-ray flash with unprecedented multi-petawatt power and brightness of 1.7 x 10(23) photons s(-1) mm(-2) mrad(-2)/0.1% bandwidth (at 1 GeV). These results bode well for new research directions in particle physics and laboratory astrophysics exploring laser plasma interactions.
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  • Weakly nonlinear Rayleigh-Taylor instability of a finite-thickness fluid layer

    Wang, L. F.   Guo, H. Y.   Wu, J. F.   Ye, W. H.   Liu, Jie   Zhang, W. Y.   He, X. T.  

    A weakly nonlinear (WN) model has been developed for the Rayleigh-Taylor instability of a finite-thickness incompressible fluid layer (slab). We derive the coupling evolution equations for perturbations on the (upper) "linearly stable" and (lower) "linearly unstable" interfaces of the slab. Expressions of temporal evolutions of the amplitudes of the perturbation first three harmonics on the upper and lower interfaces are obtained. The classical feedthrough (interface coupling) solution obtained by Taylor [Proc. R. Soc. London A 201, 192 (1950)] is readily recovered by the first-order results. Our third-order model can depict the WN perturbation growth and the saturation of linear (exponential) growth of the perturbation fundamental mode on both interfaces. The dependence of the WN perturbation growth and the slab distortion on the normalized layer thickness (kd) is analytically investigated via the third-order solutions. Comparison is made with Jacobs-Catton's formula [J. W. Jacobs and I. Catton, J. Fluid Mech. 187, 329 (1988)] of the position of the "linearly unstable" interface. Using a reduced formula, the saturation amplitude of linear growth of the perturbation fundamental mode is studied. It is found that the finite-thickness effects play a dominant role in the WN evolution of the slab, especially when kd < 1. Thus, it should be included in applications where the interface coupling effects are important, such as inertial confinement fusion implosions and supernova explosions. (C) 2014 AIP Publishing LLC.
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  • Surface plasma waves with their harmonics generation from pre-structured targets

    Pan, K. Q.   Zheng, C. Y.   He, X. T.  

    Surface plasma waves with their harmonics are generated from pre-structured targets. The harmonics are generated by coherent synchrotron emission or relativistically oscillating mirror and then resonantly amplified by surface plasma wave excitation. Two dimensional particle-in-cell simulations and the theoretical analysis show that the laser is coupled to the structured target by generating a periodic current. Some of the generated harmonics have half integer wave numbers but integer frequencies. This interesting phenomenon is controlled by the structure period of the target. (C) 2016 AIP Publishing LLC.
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  • Multiple acoustic modes stimulated Brillouin scattering in hydrogen plasmas

    Liu, Z. J.   Hao, L.   Xiang, J.   Zhu, S. P.   Zheng, C. Y.   Cao, L. H.   He, X. T.  

    Stimulated backward Brillouin scattering with a variety of ion temperatures in hydrogen plasmas is simulated. There are several separated peaks in the time-integrated scattering spectra, which indicate the existence of several acoustic modes, especially for the nearly equal temperature of ions and electrons. The phase velocities of ion acoustic modes can be from one to several ion thermal velocities. Most of the ion acoustic modes are heavily damped with a Maxwellian velocity distribution function, but they can be excited in the stimulated Brillouin scattering process due to ion trapping.
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