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  • 1
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    Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-29
    Description: Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I 0  = 3 × 10 20  W/cm 2 and pulse duration τ  = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Collisionless shocks driven by 800 nm laser pulses generate high-energy carbon ions (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-01-31
    Description: We present experimental studies on ion acceleration from diamond-like carbon (DLC) foils irradiated by 800 nm, linearly polarized laser pulses with peak intensity of 1.7 × 10 19  W/cm 2 to 3.5 × 10 19  W/cm 2 at oblique incidence. Diamond-like carbon foils are heated by the prepulse of a high-contrast laser pulse and expand to form plasmas of near-critical density caused by thermal effect before the arrival of the main pulse. It is demonstrated that carbon ions are accelerated by a collisionless shock wave in slightly overdense plasma excited by forward-moving hot electrons generated by the main pulse.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Cascaded proton acceleration by collisionless electrostatic shock (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-07-07
    Description: A new scheme for proton acceleration by cascaded collisionless electrostatic shock (CES) is proposed. By irradiating a foil target with a moderate high-intensity laser beam, a stable CES field can be induced, which is employed as the accelerating field for the booster stage of proton acceleration. The mechanism is studied through simulations and theoretical analysis, showing that a 55 MeV seed proton beam can be further accelerated to 265 MeV while keeping a good energy spread. This scheme offers a feasible approach to produce proton beams with energy of hundreds of MeV by existing available high-intensity laser facilities.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 4
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    Three-dimensional MHD simulation of the evolution of the April 2000 CME event and its induced shocks using a magnetized plasma blob model (2011)
    Wiley
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    Publication Date: 2011-04-01
    Description: A three-dimensional (3-D) time-dependent, numerical magnetohydrodynamic (MHD) model with asynchronous and parallel time-marching method is used to investigate the propagation of coronal mass ejections (CMEs) in the nonhomogenous background solar wind flow. The background solar wind is constructed based on the self-consistent source surface with observed line-of-sight of magnetic field and density from the source surface of 2.5 Rs to the Earth's orbit (215 Rs) and beyond. The CMEs are simulated by means of a very simple flux rope model: a high-density, high-velocity, and high-temperature magnetized plasma blob is superimposed on a steady state background solar wind with an initial launch direction. The dynamical interaction of a CME with the background solar wind flow between 2.5 and 220 Rs is investigated. The evolution of the physical parameters at the cobpoint, which is located at the shock front region magnetically connected to ACE spacecraft, is also investigated. We have chosen the well-defined halo-CME event of 4–6 April 2000 as a test case. In this validation study we find that this 3-D MHD model, with the asynchronous and parallel time-marching method, the self-consistent source surface as initial boundary conditions, and the simple flux rope as CME model, provide a relatively satisfactory comparison with the ACE spacecraft observations at the L1 point.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Seismic Spectral Ratios Between North Korean Nuclear Tests: Implications for Their Seismic Sources (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Seismic spectral ratios between the 3 September 2017 North Korean nuclear test (NKT2017) and four earlier Korean tests (25 May 2009, NKT2009; 12 February 2013, NKT2013; 6 January 20016, NKT2016J; and 9 September 2016, NKT2016S) are investigated. All the observed teleseismic P wave spectral ratios exhibit a unique notch at approximately 2.5 Hz, but it is not observed for spectral ratios of regional P and Lg waves. Meanwhile, for a given event pair, the network‐averaged Lg wave spectral ratio is similar to that of regional P wave, but with the explosions' source corner frequencies significantly reduced, supporting the conjecture by Fisk (2006, https://doi.org/10.1785/0120060023). We demonstrated that the observed notch of teleseismic P wave spectral ratios may be well modeled with interference between pP and P waves with an apparent pP‐P time delay ΔtpP of about 0.4 s for NKT2017, while regional P wave spectral ratios may be well fitted with source spectral ratios predicted by classical explosion source models including Mueller and Murphy (1971, https://doi.org/10.2172/4107998) (MM71), Denny and Johnson (1991, https://doi.org/10.1029/gm065p0001) (DJ91), and their two hybrids. Via the above modeling, yield sizes of the explosions and the depth of burials of NKT2009–2016S are determined as functions of NKT2017's buried depth h0. Our result indicate that, for h0 in the range of 600–1,100 m, the MM71‐related models give yield estimations about 100–300 kt for NKT2017, 3–7 kt for NKT2009, 6–15 kt for NKT2013 and NKT2016J, and 10–25 kt for NKT2016S, while yield sizes obtained by model DJ91 are much smaller. Nevertheless, for all the above source models, the obtained depths of burial estimations of NKT2009–2016S are always significantly smaller than NKT2017's depth of burial h0.
    Print ISSN: 2169-9313
    Electronic ISSN: 2169-9356
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Three-dimensional MHD simulation of two coronal mass ejections' propagation and interaction using a successive magnetized plasma blobs model (2011)
    Wiley
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    Publication Date: 2011-09-24
    Description: A three-dimensional (3-D), time-dependent, numerical magnetohydrodynamic (MHD) model is used to investigate the evolution and interaction of two coronal mass ejections (CMEs) in the nonhomogeneous ambient solar wind. The background solar wind is constructed on the basis of the self-consistent source surface with observed line of sight of magnetic field and density from the source surface of 2.5 Rs to Earth's orbit (215 Rs) and beyond. The two successive CMEs occurring on 28 March 2001 and forming a multiple magnetic cloud in interplanetary space are chosen as a test case, in which they are simulated by means of a two high-density, high-velocity, and high-temperature magnetized plasma blobs model, and are successively ejected into the nonhomogeneous background solar wind medium along different initial launch directions. The dynamical propagation and interaction of the two CMEs between 2.5 and 220 Rs are investigated. Our simulation results show that, although the two CMEs are separated by 10 h, the second CME is able to overtake the first one and cause compound interactions and an obvious acceleration of the shock. At the L1 point near Earth the two resultant magnetic clouds in our simulation are consistent with the observations by ACE. In this validation study we find that this 3-D MHD model, with the self-consistent source surface as the initial boundary condition and the magnetized plasma blob as the CME model, is able to reproduce and explain some of the general characters of the multiple magnetic clouds observed by satellite.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Using a 3-D spherical plasmoid to interpret the Sun-to-Earth propagation of the 4 November 1997 coronal mass ejection event (2012)
    Wiley
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    Publication Date: 2012-01-10
    Description: We present the time-dependent propagation of a Sun-Earth connection event that occurred on 4 November 1997 using a three-dimensional (3-D) numerical magnetohydrodynamics (MHD) simulation. A global steady state solar wind for this event is obtained by a 3-D SIP-CESE MHD model with Parker's 1-D solar wind solution and measured photospheric magnetic fields as the initial values. Then, superposed on the quiet background solar wind, a spherical plasmoid is used to mimic the 4 November 1997 coronal mass ejection (CME) event. The CME is assumed to arise from the evolution of a spheromak magnetic structure with high-speed, high-pressure, and high-plasma-density plasmoid near the Sun. Moreover, the axis of the initial simulated CME is put at S14W34 to conform to the observed location of this flare/CME event. The result has provided us with a relatively satisfactory comparison with the Wind spacecraft observations, such as southward interplanetary magnetic field and large-scale smooth rotation of the magnetic field associated with the CME.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Target normal sheath acceleration of foil ions by laser-trapped hot electrons from a long subcritical-density preplasma (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-11
    Description: In a long subcritical density plasma, an ultrashort ultraintense laser pulse can self-organize into a fast but sub-relativistic propagating structure consisting of the modulated laser light and a large number of trapped electrons from the plasma. Upon impact of the structure with a solid foil target placed in the latter, the remaining laser light is reflected, but the dense and hot trapped electrons pass through the foil, together with the impact-generated target-frontsurface electrons to form a dense hot electron cloud at the back of the target suitable for enhancing target normal sheath acceleration of the target-backsurface ions. The accelerated ions are well collimated and of high charge and energy densities, with peak energies a full order of magnitude higher than that from target normal sheath acceleration without the subcritical density plasma. In the latter case, the space-charge field accelerating the ions is limited since they are formed only by the target-frontsurface electrons during the very short instant of laser reflection.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 9
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    Proton beam shaped by “particle lens” formed by laser-driven hot electrons (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-05-27
    Description: Two-dimensional tailoring of a proton beam is realized by a “particle lens” in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a “fountain-like” pattern when these hot electrons diffuse after propagating a distance.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 10
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    2D Photonic Crystal Layer Assisted Thiosilicate Ceramic Plate with Red-emitting Film for High Quality w-LEDs (2017)
    Wiley
    Details
    Publication Date: 2017-06-22
    Description: In this work, we have succeeded in obtaining high quality warm w -LEDs by adopting hybrid two-dimensional (2D) structure of SiN x photonic crystal layer (PCL) assisted cyan-emitting ceramic-plate thiosilicate SrLa 2 Si 2 S 8 :Ce 3+ with red-emitting film SrLiAl 3 N 4 :Eu 2+ phosphor on a 430 nm blue LED chip at 350 mA. 2D SiN x PCL was capped with thiosilicate is because it can enhance the luminous efficacy and maintain the low correlated color temperature (CCT) and high color-rendering index (CRI). High luminous efficacy (82.3 lm/W), high special CRI (R 9 = 75) as well as the low CCT (5431 K) of the optimal w -LED was obtained due to the assistances of 2D SiN x PCL and narrow-band red-emitting phosphor with the doping percentage at 10 wt%. The synthesis processes, structural analysis, optical properties and LED device performances were detailed investigated to find out the relationship between the optimum composition and good optical properties. Based on intriguing luminescence properties by the 2D SiN x PCL and red-emitting film phosphor introducing, we proclaim this method could also have high potential application in other phosphor-converted w -LEDs. This article is protected by copyright. All rights reserved.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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