87 results on '"Takayoshi Sano"'
Search Results
2. Isochoric heating of solid-density plasmas beyond keV temperature by fast thermal diffusion with relativistic picosecond laser light
- Author
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Naoki Higashi, Natsumi Iwata, Takayoshi Sano, Kunioki Mima, and Yasuhiko Sentoku
- Abstract
The interaction of relativistic short-pulse lasers with matter produces fast electrons with over megaampere currents, which supposedly heats a solid target isochorically and forms a hot dense plasma. In a picosecond timescale, however, thermal diffusion from hot preformed plasma turns out to be the dominant process of isochoric heating. We describe a heating process, fast thermal diffusion, launched from the preformed plasma heated resistively by the fast electron current. We demonstrate the fast thermal diffusion in the keV range in a solid density plasma by a series of one-dimensional particle-in-cell simulations. A theoretical model of the fast thermal diffusion is developed and we derive the diffusion speed as a function of the laser amplitude and target density. Under continuous laser irradiation, the diffusion front propagates at a constant speed in uniform plasma. Our model can provide a guideline for fast isochoric heating using future kilojoule petawatt lasers.
- Published
- 2022
3. Demonstration of a spherical plasma mirror for the counter-propagating kilojoule-class petawatt LFEX laser system
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Sadaoki Kojima, Yuki Abe, Eisuke Miura, Tetsuo Ozaki, Kohei Yamanoi, Tomokazu Ikeda, Yubo Wang, Jinyuan Dun, Shuwang Guo, Tamaki Maekawa, Ryunosuke Takizawa, Hiroki Morita, Shoui Asano, Yasunobu Arikawa, Hiroshi Sawada, Katsuhiro Ishii, Ryohei Hanayama, Shinichiro Okihara, Yoneyoshi Kitagawa, Yasuhiro Kajimura, Alessio Morace, Hiroyuki Shiraga, Keisuke Shigemori, Atsushi Sunahara, Natsumi Iwata, Takayoshi Sano, Yasuhiko Sentoku, Tomoyuki Johzaki, Masaharu Nishikino, Akifumi Iwamoto, Kenichi Nagaoka, Hitoshi Sakagami, Shinsuke Fujioka, and Yoshitaka Mori
- Subjects
Atomic and Molecular Physics, and Optics - Abstract
A counter-propagating laser-beam platform using a spherical plasma mirror was developed for the kilojoule-class petawatt LFEX laser. The temporal and spatial overlaps of the incoming and redirected beams were measured with an optical interferometer and an x-ray pinhole camera. The plasma mirror performance was evaluated by measuring fast electrons, ions, and neutrons generated in the counter-propagating laser interaction with a Cu-doped deuterated film on both sides. The reflectivity and peak intensity were estimated as ∼50% and ∼5 × 1018 W/cm2, respectively. The platform could enable studies of counter-streaming charged particles in high-energy-density plasmas for fundamental and inertial confinement fusion research.
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- 2022
4. Pulse duration constraint of whistler waves in magnetized dense plasma
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Yasuhiko Sentoku, Masayasu Hata, Hitoshi Sakagami, Hideo Nagatomo, and Takayoshi Sano
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Brillouin zone ,Physics ,Amplitude ,Whistler ,Physics::Plasma Physics ,Brillouin scattering ,Quantum electrodynamics ,Physics::Space Physics ,Pulse duration ,Plasma ,Instability ,Magnetic field - Abstract
Interactions between large-amplitude laser light and strongly magnetized dense plasma have been investigated by one- and two-dimensional electromagnetic particle-in-cell simulations. Since whistler waves have no critical density, they can propagate through plasmas beyond the critical density in principle. However, we have found the propagation of whistler waves is restricted significantly by the stimulated Brillouin scattering. It is confirmed that the period during which the whistler wave can propagate in overcritical plasmas is proportional to the growth time of the ion-acoustic wave via the Brillouin instability. The allowable pulse duration of the whistler wave has a power-law dependence on the amplitude of the whistler wave and the external magnetic field.
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- 2021
5. Enhancement of Ablative Rayleigh-Taylor Instability Growth by Thermal Conduction Suppression in a Magnetic Field
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Toshihiro Somekawa, Yasunobu Arikawa, Hiroki Morita, King Fai Farley Law, Kazuki Matsuo, Takayoshi Sano, Hideo Nagatomo, and Shinsuke Fujioka
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Materials science ,Condensed matter physics ,Field (physics) ,Gyroradius ,FOS: Physical sciences ,General Physics and Astronomy ,Electron ,Thermal conduction ,Instability ,Physics - Plasma Physics ,Magnetic field ,Plasma Physics (physics.plasm-ph) ,Physics::Plasma Physics ,Magnetohydrodynamic drive ,Rayleigh–Taylor instability - Abstract
Ablative Rayleigh-Taylor instability growth was investigated to elucidate the fundamental physics of thermal conduction suppression in a magnetic field. Experiments found that unstable modulation growth is faster in an external magnetic field. This result was reproduced by a magnetohydrodynamic simulation based on a Braginskii model of electron thermal transport. An external magnetic field reduces the electron thermal conduction across the magnetic field lines because the Larmor radius of the thermal electrons in the field is much shorter than the temperature scale length. Thermal conduction suppression leads to spatially nonuniform pressure and reduced thermal ablative stabilization, which in turn increases the growth of ablative Rayleigh-Taylor instability.
- Published
- 2021
6. Ion acceleration at two collisionless shocks in a multicomponent plasma
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Nigel Woolsey, R. Kumar, Leonard N. K. Döhl, Takayoshi Sano, Alessio Morace, and Youichi Sakawa
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Hydrogen ,FOS: Physical sciences ,chemistry.chemical_element ,Flux ,01 natural sciences ,Instability ,010305 fluids & plasmas ,Ion ,Physics - Space Physics ,Physics::Plasma Physics ,0103 physical sciences ,010306 general physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Plasma ,Physics - Plasma Physics ,Space Physics (physics.space-ph) ,Shock (mechanics) ,Plasma Physics (physics.plasm-ph) ,Particle acceleration ,chemistry ,Physics::Space Physics ,Atomic physics ,Astrophysics - High Energy Astrophysical Phenomena ,Vector potential - Abstract
Intense laser-plasma interactions are an essential tool for the laboratory study of ion acceleration at a collisionless shock. With two-dimensional particle-in-cell calculations of a multicomponent plasma we observe two electrostatic collisionless shocks at two distinct longitudinal positions when driven with a linearly polarized laser at normalized laser vector potential ${a}_{0}$ that exceeds 10. Moreover, these shocks, associated with protons and carbon ions, show a power-law dependence on ${a}_{0}$ and accelerate ions to different velocities in an expanding upstream with higher flux than in a single-component hydrogen or carbon plasma. This results from an electrostatic ion two-stream instability caused by differences in the charge-to-mass ratio of different ions. Particle acceleration in collisionless shocks in multicomponent plasma are ubiquitous in space and astrophysics, and these calculations identify the possibility for studying these complex processes in the laboratory.
- Published
- 2021
7. Shock-induced polymorphic transitions of PbF2 up to 1 TPa and their implications for the universal behavior of shocked AX2 compounds
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Tsutomu Mashimo, Xun Liu, Norimasa Ozaki, Chang Gao, Takayoshi Sano, Shintaro Morioka, Haijun Huang, Ryosuke Kodama, Gang Yang, Kohei Miyanishi, and Williams J. Nellis
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Physics ,Shock (fluid dynamics) ,Phase (matter) ,0103 physical sciences ,Analytical chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,010306 general physics ,0210 nano-technology ,01 natural sciences - Abstract
Hugoniot data for $\mathrm{Pb}{\mathrm{F}}_{2}$ single crystals were measured for pressures up to 1 TPa through gas gun and laser shock experiments. Experimental results show that $\mathrm{Pb}{\mathrm{F}}_{2}$ transforms to a less compressible phase at 29 GPa and possibly melts at 57 GPa. Quantum molecular-dynamics simulations were also performed to calculated the liquid Hugoniot for $\mathrm{Pb}{\mathrm{F}}_{2}$. The simulated results are in good agreement with the experimental results, supporting the high-pressure phase is liquid. The current study, combined with previous studies on $\mathrm{Ti}{\mathrm{O}}_{2}, \mathrm{Si}{\mathrm{O}}_{2}$, and $\mathrm{Ca}{\mathrm{F}}_{2}$, suggests that for $A{X}_{2}$ compounds, decreasing of Hugoniot slope can be taken as an indication of melting, and the Hugoniot slope approaches 1.2 at ultrahigh pressure.
- Published
- 2021
8. Alfven number for the Richtmyer-Meshkov instability in magnetized plasmas
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Takayoshi Sano
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Field (physics) ,Shock (fluid dynamics) ,Richtmyer–Meshkov instability ,FOS: Physical sciences ,Astronomy and Astrophysics ,Instability ,Physics - Plasma Physics ,Magnetic field ,Plasma Physics (physics.plasm-ph) ,symbols.namesake ,Atwood number ,Space and Planetary Science ,Quantum electrodynamics ,Computer Science::Multimedia ,symbols ,Magnetohydrodynamics ,Astrophysics - High Energy Astrophysical Phenomena ,Lorentz force - Abstract
Magnetohydrodynamical evolution of the Richtmyer-Meshkov instability (RMI) is investigated by two-dimensional MHD simulations. The RMI is suppressed by a strong magnetic field, whereas the RMI amplifies an ambient magnetic field by many orders of magnitude if the seed field is weak. We have found that the suppression and amplification processes can be evaluated continuously along with the amplitude of the Alfv\'en number $R_A$, which is defined as the ratio of the linear growth velocity of the RMI to the Alfv\'en speed at the interface. When the Alfv\'en number is less than unity, the Lorentz force acting on the fluid mitigates the unstable motion of the RMI significantly, and the interface oscillates stably in this limit. If $R_A \gtrsim 1$, on the other hand, the surface modulation increases due to the growth of the RMI. The maximum strength of the magnetic field is enhanced up to by a factor of $R_A$. This critical feature is universal and independent of the initial Mach number of the incident shock, the Atwood number, corrugation amplitude, and even the direction of the initial magnetic field., Comment: 11 pages, 8 figures, 1 table, accepted for publication in ApJ
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- 2021
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9. OPTAB: Public code for generating gas opacity tables for radiation hydrodynamics simulations
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Shigenobu Hirose, Peter Hauschildt, Takashi Minoshima, Kengo Tomida, and Takayoshi Sano
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Earth and Planetary Astrophysics (astro-ph.EP) ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Solar and Stellar Astrophysics (astro-ph.SR) ,ComputingMethodologies_COMPUTERGRAPHICS ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We have developed a public code, Optab, that outputs Rosseland, Planck, and two-temperature Planck mean gas opacity tables for radiation hydrodynamics simulations in astrophysics. The code is developed for modern high-performance computing, being written in Fortran 90 and using Message Passing Interface and Hierarchical Data Format, Version 5. The purpose of this work is to provide a platform on which users can generate opacity tables for their own research purposes. Therefore, the code has been designed so that a user can easily modify, change, or add opacity sources in addition to those already implemented, which include bremsstrahlung, photoionization, Rayleigh scattering, line absorption, and collision-induced absorption. In this paper, we provide details of the opacity calculations in our code and present validation tests to evaluate the performance of our code., Astronomy and Astrophysics, in press
- Published
- 2022
10. Shock response and degassing reactions of calcite at planetary impact conditions
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Takeshi Matsuoka, M. Guarguaglini, Alessandra Ravasio, Ryosuke Kodama, Keiya Fukui, Norimasa Ozaki, Kohei Miyanishi, Nobuki Kamimura, Kento Katagiri, Takayoshi Sano, Alessandra Benuzzi-Mounaix, Yuhei Umeda, and Toshimori Sekine
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Calcite ,chemistry.chemical_compound ,Materials science ,chemistry ,Shock response spectrum ,Mineralogy - Abstract
Calcite (CaCO3) as a planetary material is a source to the atmospheric carbon dioxide through degassing by high-velocity impact events. Revealing the behavior of calcite in the extreme pressure and temperature conditions is required to understand the impact-induced degassing phenomena. Here we report laboratory investigations of shock- compressed calcite beyond the impact velocity of 12 km/s (faster than escape velocity from the Earth). The present precise shock measurements elucidate the shape of the calcite Hugoniot curve continuously passing through the melting and metallization states up to a pressure of 1000 GPa (= 10-million atmospheres) or a corresponding impact velocity of 30 km/s, allowing us to predict the post-shock residual temperatures and the dominant carbon oxide species in the impact aftermath. These predictions suggest that CO emission is much more dominant than CO2 at the impact velocities of ∼10 km/s and above, affecting the planetary atmospheric chemistry, greenhouse processes, and environmental changes during planetary evolution.
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- 2020
11. Plasma concept for generating circularly polarized electromagnetic waves with relativistic amplitude
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Takayoshi Sano, Yusuke Tatsumi, Yasuhiko Sentoku, and Masayasu Hata
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Physics ,business.industry ,Linear polarization ,FOS: Physical sciences ,Plasma ,Laser ,01 natural sciences ,Electromagnetic radiation ,Physics - Plasma Physics ,010305 fluids & plasmas ,law.invention ,Magnetic field ,Plasma Physics (physics.plasm-ph) ,Amplitude ,law ,Physics::Plasma Physics ,0103 physical sciences ,Photonics ,Atomic physics ,010306 general physics ,business ,FOIL method ,Optics (physics.optics) ,Physics - Optics - Abstract
Propagation features of circularly polarized (CP) electromagnetic waves in magnetized plasmas are determined by the plasma density and the magnetic field strength. This property can be applied to design a unique plasma photonic device for intense short-pulse lasers. We have demonstrated by numerical simulations that a thin plasma foil under an external magnetic field works as a polarizing plate to separate a linearly polarized laser into two CP waves traveling in the opposite direction. This plasma photonic device has an advantage for generating intense CP waves even with a relativistic amplitude. For various research purposes, intense CP lights are strongly required to create high energy density plasmas in the laboratory., 9 pages, 8 figures, accepted for publication in PRE
- Published
- 2020
12. Suppression of the Richtmyer-Meshkov instability due to a density transition layer at the interface
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Kazuki Ishigure, Francisco Cobos-Campos, and Takayoshi Sano
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Range (particle radiation) ,Shock (fluid dynamics) ,Condensed matter physics ,Richtmyer–Meshkov instability ,FOS: Physical sciences ,Kinetic energy ,01 natural sciences ,Instability ,Physics - Plasma Physics ,010305 fluids & plasmas ,Plasma Physics (physics.plasm-ph) ,Discontinuity (linguistics) ,Wavelength ,Modulation ,0103 physical sciences ,Astrophysics - High Energy Astrophysical Phenomena ,010306 general physics - Abstract
We have investigated the effects of a smooth transition layer at the contact discontinuity on the growth of the Richtmyer-Meshkov instability (RMI) by hydrodynamic numerical simulations and derived an empirical condition for the suppression of the instability. The transition layer has little influence on the RMI when the thickness $L$ is narrower than the wavelength of an interface modulation $\lambda$. However, if the transition layer becomes broader than $\lambda$, the perturbed velocity associated with the RMI is reduced considerably. The suppression condition is interpreted as the cases that the shock transit time through the transition layer is longer than the sound crossing time of the modulation wavelength. The fluctuation kinetic energy decreases as $L^{-p}$ with $p = 2.5$, which indicates that the growth velocity of the RMI decreases in proportion to $L^{-p/2}$ by the presence of the transition layer. This feature is found to be quite universal and appeared in a wide range of shock-interface interactions., Comment: 11 pages, 8 figures, 1 table, accepted for publication in PRE
- Published
- 2020
13. Shock Response of Full Density Nanopolycrystalline Diamond
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Tetsuo Irifune, Yuhei Umeda, Kohei Miyanishi, Nobuki Kamimura, Ryosuke Kodama, Toshimori Sekine, Norimasa Ozaki, Kento Katagiri, and Takayoshi Sano
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Full density ,Materials science ,Static compression ,Significant difference ,General Physics and Astronomy ,Diamond ,engineering.material ,01 natural sciences ,Shock response spectrum ,0103 physical sciences ,engineering ,Composite material ,010306 general physics ,Grain boundary strengthening - Abstract
Hugoniot of full-dense nanopolycrystalline diamond (NPD) was investigated up to 1600 GPa. The Hugoniot elastic limit of NPD is 208 ($\ifmmode\pm\else\textpm\fi{}14$) GPa, which is more than twice as high as that of single-crystal diamond. The Hugoniot of NPD is stiffer than that of single-crystal diamond up to 500 GPa, while no significant difference is observed at higher pressures where the elastic precursor is overdriven by a following plastic wave. These findings confirm that the grain boundary strengthening effect recognized in static compression experiments is also effective against high strain-rate dynamic compressions.
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- 2020
14. Optical properties of shock-compressed diamond up to 550 GPa
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Norimasa Ozaki, Kento Katagiri, Kohei Miyanishi, Nobuki Kamimura, Toshimori Sekine, Takayoshi Sano, Ryosuke Kodama, and Yuhei Umeda
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Shock wave ,Materials science ,Condensed matter physics ,Shock (fluid dynamics) ,Diamond ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Compression (physics) ,01 natural sciences ,0103 physical sciences ,engineering ,010306 general physics ,0210 nano-technology ,Refractive index - Abstract
A series of shock wave experiments were conducted to measure the optical properties of single-crystal diamond $\ensuremath{\langle}100\ensuremath{\rangle}$ in the pressure regime between 60 and 550 GPa. The results show that the transparency limit of diamond at 532 nm is $\ensuremath{\sim}170\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. When the applied pressure in diamond is lower than its Hugoniot elastic limit (HEL), diamond remains transparent during both compression and release processes. At the pressures between the HEL and the limit of its transparency, however, diamond is found to be transparent only while the compression is maintained and gradually loses its transparency during the subsequent release process. We also found that the refractive index of single-crystal diamond \ensuremath{\langle}100\ensuremath{\rangle} monotonically increases as density increases to the limit of its transparency, in contrast to the previous static reports on continuous decrease of refractive index with increasing pressure up to 40 GPa.
- Published
- 2020
15. Thermonuclear Fusion Triggered by Collapsing Standing Whistler Waves in Magnetized Overdense Plasmas
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Shinsuke Fujioka, Yasuhiko Sentoku, Yoshitaka Mori, Takayoshi Sano, and Kunioki Mima
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Thermonuclear fusion ,Whistler ,FOS: Physical sciences ,Plasma ,01 natural sciences ,Electromagnetic radiation ,Physics - Plasma Physics ,010305 fluids & plasmas ,Ion ,Plasma Physics (physics.plasm-ph) ,Physics::Plasma Physics ,0103 physical sciences ,Neutron source ,Nuclear fusion ,Atomic physics ,010306 general physics ,Astrophysics - High Energy Astrophysical Phenomena ,Inertial confinement fusion - Abstract
Thermal fusion plasmas initiated by standing whistler waves are investigated numerically by two- and one-dimensional Particle-in-Cell simulations. When a standing whistler wave collapses due to the wave breaking of ion plasma waves, the energy of the electromagnetic waves transfers directly to the ion kinetic energy. Here we find that the ion heating by the standing whistler wave is operational even in multi-dimensional simulations of multi-ion species targets, such as deuterium-tritium (DT) ices and solid ammonia borane (H$_6$BN). The energy conversion efficiency to ions becomes as high as 15% of the injected laser energy, which depends significantly on the target thickness and laser pulse duration. The ion temperature could reach a few tens of keV or much higher if appropriate laser-plasma conditions are selected. DT fusion plasmas generated by this method must be useful as efficient neutron sources. Our numerical simulations suggest that the neutron generation efficiency exceeds 10$^9$ n/J per steradian, which is beyond the current achievements of the state-of-the-art laser experiments. The standing whistler wave heating would expand the experimental possibility for an alternative ignition design of magnetically confined laser fusion, and also for more difficult fusion reactions including the aneutronic proton-boron reaction., Comment: 16 pages, 11 figures, accepted for publication in PRE
- Published
- 2020
- Full Text
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16. Pressure amplification effect of using resorcinol/formaldehyde foam ablators in laser-shock experiments
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Ryosuke Kodama, Kohei Yamanoi, Norimasa Ozaki, Kento Katagiri, and Takayoshi Sano
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inorganic chemicals ,Polypropylene ,Shock wave ,Physics ,Resorcinol ,respiratory system ,Velocimetry ,Condensed Matter Physics ,Laser ,complex mixtures ,law.invention ,Shock (mechanics) ,chemistry.chemical_compound ,chemistry ,law ,Composite material ,Quartz ,Pyrometer - Abstract
Resorcinol/formaldehyde (RF) foam-aluminum-quartz-layered targets were shock compressed up to 0.9 TPa in quartz to quantitatively evaluate the pressure-amplification effect of using a low-density RF foam as an ablator. The velocimetry and pyrometry were used to obtain the shock pressure and temperature in the quartz. The results show the use of an RF foam ablator with a density of 100 mg/cm3 increases the peak pressure of quartz by 76 (±11)% compared to the case with a polypropylene ablator. Our results also confirm that preheating of the quartz ahead of the shock wave due to the x rays produced in the ablated foam is negligible, indicating that a low-density RF foam is an ideal ablator material for laser-shock experiments.
- Published
- 2021
17. Spatial and temporal plasma evolutions of magnetic reconnection in laser produced plasmas
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Takayoshi Sano, Nima Bolouki, Toseo Moritaka, Ryo Yamazaki, Kiichiro Uchino, C. H. Chen, C. W. Peng, H. Shimogawara, Shuichi Matsukiyo, Kentaro Tomita, M. Koenig, Yuta Sato, N. Khasanah, Sara Tomita, Youichi Sakawa, T. Y. Huang, Yasuhiro Kuramitsu, Y. Hara, Y. Shoji, and S. Tomiya
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Physics ,Nuclear and High Energy Physics ,Framing (visual arts) ,Radiation ,Bubble ,Magnetic reconnection ,Plasma ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Nanoflares ,Optical diagnostics ,Physics::Plasma Physics ,law ,Physics::Space Physics ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Atomic physics ,010306 general physics ,Laser beams - Abstract
Magnetic reconnection is experimentally investigated in laser produced plasmas. By irradiating a solid target with a high-power laser beam, a magnetic bubble is generated due to the Biermann effect. When two laser beams with finite focal spot displacements are utilized, two magnetic bubbles are generated, and the magnetic reconnection can take place. We measure the spatial and temporal plasma evolutions with optical diagnostics using framing camera. We observed the plasma jets, which are considered to be reconnection out flows. Spatial and temporal scales of the plasma jets are much larger than those of laser. The magnetic reconnection time has been estimated from the expansion velocity, which is consistent with the Sweet-Parker model.
- Published
- 2017
18. Nonlinear Dynamics of Non-uniform Current-Vortex Sheets in Magnetohydrodynamic Flows
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Takayoshi Sano, Chihiro Matsuoka, and Katsunobu Nishihara
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01 natural sciences ,010305 fluids & plasmas ,リヒトマイヤー・メシュコフ不安定性 ,Current sheet ,Richtmyer-Meshkov instability ,Condensed Matter::Superconductivity ,0103 physical sciences ,Vortex sheet ,MHD interfacial instability ,Magnetohydrodynamic drive ,010306 general physics ,Physics ,Richtmyer–Meshkov instability ,Surface Alfven wave ,Applied Mathematics ,電磁流体 ,General Engineering ,Mechanics ,アルフベン波 ,Non-uniform current-vortex sheet ,Vortex ,Magnetic field ,Alfven number ,Modeling and Simulation ,電流渦層 ,Physics::Space Physics ,Potential flow ,Magnetohydrodynamics ,アルフベン数 - Abstract
A theoretical model is proposed to describe fully nonlinear dynamics of interfaces in two-dimensional MHD flows based on an idea of non-uniform current-vortex sheet. Application of vortex sheet model to MHD flows has a crucial difficulty because of non-conservative nature of magnetic tension. However, it is shown that when a magnetic field is initially parallel to an interface, the concept of vortex sheet can be extended to MHD flows (current-vortex sheet). Two-dimensional MHD flows are then described only by a one-dimensional Lagrange parameter on the sheet. It is also shown that bulk magnetic field and velocity can be calculated from their values on the sheet. The model is tested by MHD Richtmyer–Meshkov instability with sinusoidal vortex sheet strength. Two-dimensional ideal MHD simulations show that the nonlinear dynamics of a shocked interface with density stratification agrees fairly well with that for its corresponding potential flow. Numerical solutions of the model reproduce properly the results of the ideal MHD simulations, such as the roll-up of spike, exponential growth of magnetic field, and its saturation and oscillation. Nonlinear evolution of the interface is found to be determined by the Alfven and Atwood numbers. Some of their dependence on the sheet dynamics and magnetic field amplification are discussed. It is shown by the model that the magnetic field amplification occurs locally associated with the nonlinear dynamics of the current-vortex sheet. We expect that our model can be applicable to a wide variety of MHD shear flows.
- Published
- 2016
19. Full particle-in-cell simulation of the interaction between two plasmas for laboratory experiments on the generation of magnetized collisionless shocks with high-power lasers
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Hiroaki Toda, N. Ishizaka, S. Sei, Takayuki Umeda, Youichi Sakawa, S. Kakuchi, Ryo Yamazaki, I. Miyata, Yutaka Ohira, Sara Tomita, Shuichi Matsukiyo, Takayoshi Sano, Shuta J. Tanaka, Taichi Morita, and Yasuhiro Kuramitsu
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Electron density ,FOS: Physical sciences ,01 natural sciences ,Gyration ,010305 fluids & plasmas ,law.invention ,Ion ,Piston ,law ,Physics::Plasma Physics ,0103 physical sciences ,010306 general physics ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Shock (fluid dynamics) ,Plasma ,Condensed Matter Physics ,equipment and supplies ,Physics - Plasma Physics ,Magnetic field ,Plasma Physics (physics.plasm-ph) ,Physics::Space Physics ,Particle-in-cell ,Atomic physics ,Astrophysics - High Energy Astrophysical Phenomena ,human activities - Abstract
A preliminary numerical experiment is conducted for laboratory experiments on the generation of magnetized collisionless shocks with high-power lasers by using one-dimensional particle-in-cell simulation. The present study deals with the interaction between a moving aluminum plasma and a nitrogen plasma at rest. In the numerical experiment, the nitrogen plasma is unmagnetized or magnetized by a weak external magnetic field. Since the previous study suggested the generation of a spontaneous magnetic field in the piston (aluminum) plasma due to the Biermann battery, the effect of the magnetic field is of interest. Sharp jumps of the electron density and magnetic field are observed around the interface between the two plasmas as long as one of the two plasmas is magnetized, which indicates the formation of tangential electron-magneto-hydro-dynamic discontinuity. When the aluminum plasma is magnetized, strong compression of both the density and the magnetic field takes place in the pure aluminum plasma during the gyration of nitrogen ions in the aluminum plasma region. The formation of a shock downstream is obtained from the shock jump condition. The results suggest that the spontaneous magnetic field in the piston (aluminum) plasma plays an essential role in the formation of a perpendicular collisionless shock., ファイル公開:2020-03-05
- Published
- 2019
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20. Ultrafast Wave-Particle Energy Transfer in the Collapse of Standing Whistler Waves
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Takayoshi Sano, Daiki Kawahito, Masayasu Hata, Kunioki Mima, and Yasuhiko Sentoku
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Whistler ,FOS: Physical sciences ,Plasma ,Space physics ,01 natural sciences ,Electromagnetic radiation ,Physics - Plasma Physics ,Space Physics (physics.space-ph) ,010305 fluids & plasmas ,Ion ,Computational physics ,Standing wave ,Plasma Physics (physics.plasm-ph) ,Physics - Space Physics ,Physics::Plasma Physics ,0103 physical sciences ,Physics::Space Physics ,Reflection (physics) ,Electron temperature ,010306 general physics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
Efficient energy transfer from electromagnetic waves to ions has been demanded to control laboratory plasmas for various applications and could be useful to understand the nature of space and astrophysical plasmas. However, there exists a severe unsolved problem that most of the wave energy is converted quickly to electrons, but not to ions. Here, an energy conversion process to ions in overdense plasmas associated with whistler waves is investigated by numerical simulations and theoretical model. Whistler waves propagating along a magnetic field in space and laboratories often form the standing waves by the collision of counter-propagating waves or through the reflection. We find that ions in the standing whistler waves acquire a large amount of energy directly from the waves in a short timescale comparable to the wave oscillation period. Thermalized ion temperature increases in proportion to the square of the wave amplitude and becomes much higher than the electron temperature in a wide range of wave-plasma conditions. This efficient ion-heating mechanism applies to various plasma phenomena in space physics and fusion energy sciences., Comment: 11 pages, 9 figures, 1 table, accepted for publication in PRE
- Published
- 2019
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21. Peta-Pascal Pressure Driven by Fast Isochoric Heating with Multi-Picosecond Intense Laser Pulse
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Hiroyuki Shiraga, Shohei Sakata, King Fai Farley Law, Sadaoki Kojima, Mitsuo Nakai, Kunioki Mima, Yoshiki Nakata, Takayoshi Sano, Yuki Abe, Atsushi Sunahara, Kohei Yamanoi, Yugo Ochiai, Seung Ho Lee, Shinsuke Fujioka, Yuki Iwasa, Tetsuo Ozaki, Takayoshi Norimatsu, Yasunobu Arikawa, Hiroshi Sawada, Yasuhiko Sentoku, Tomoyuki Johzaki, Masayasu Hata, Shigeki Tokita, Naoki Higashi, Natsumi Iwata, Hiroki Morita, Alessio Morace, Akifumi Yogo, Ryosuke Kodama, Hiroshi Azechi, Hideo Nagatomo, Hitoshi Sakagami, Kazuki Matsuo, and Junji Kawanaka
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Materials science ,Isochoric process ,General Physics and Astronomy ,Implosion ,FOS: Physical sciences ,Plasma ,Electron ,Laser ,7. Clean energy ,01 natural sciences ,Physics - Plasma Physics ,3. Good health ,law.invention ,Pulse (physics) ,Magnetic field ,Plasma Physics (physics.plasm-ph) ,Physics::Plasma Physics ,law ,Physics::Space Physics ,0103 physical sciences ,Atomic physics ,010306 general physics ,Intensity (heat transfer) - Abstract
Fast isochoric laser heating is a scheme to heat a matter with relativistic-intensity ($>$ 10$^{18}$ W/cm$^2$) laser pulse or X-ray free electron laser pulse. The fast isochoric laser heating has been studied for creating efficiently ultra-high-energy-density (UHED) state. We demonstrate an fast isochoric heating of an imploded dense plasma using a multi-picosecond kJ-class petawatt laser with an assistance of externally applied kilo-tesla magnetic fields for guiding fast electrons to the dense plasma.The UHED state with 2.2 Peta-Pascal is achieved experimentally with 4.6 kJ of total laser energy that is one order of magnitude lower than the energy used in the conventional implosion scheme. A two-dimensional particle-in-cell simulation reveals that diffusive heating from a laser-plasma interaction zone to the dense plasma plays an essential role to the efficient creation of the UHED state., 8 pages, 4 figures, 1 table
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- 2019
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22. Anomalous plasma acceleration in colliding high-power laser-produced plasmas
- Author
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Ryo Yamazaki, Takayoshi Sano, Sara Tomita, S. Sei, I. Miyata, S. Egashira, Masahiro Hoshino, Kentaro Tomita, S. Tomiya, Keisuke Nagashima, M. Ota, Youichi Sakawa, Masafumi Edamoto, Shuichi Matsukiyo, N. Ishizaka, Yasuhiro Kuramitsu, Taichi Morita, Shuta J. Tanaka, Yutaro Itadani, H. Toda, S. Kakuchi, Yutaka Ohira, and R. Kumar
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Thomson scattering ,FOS: Physical sciences ,Magnetic reconnection ,Plasma ,Condensed Matter Physics ,Plasma acceleration ,01 natural sciences ,Physics - Plasma Physics ,010305 fluids & plasmas ,Magnetic field ,Computational physics ,Plasma Physics (physics.plasm-ph) ,Acceleration ,Flow velocity ,Physics::Plasma Physics ,0103 physical sciences ,Physics::Space Physics ,Magnetic tension force ,Physics::Accelerator Physics ,Astrophysics - High Energy Astrophysical Phenomena ,010306 general physics - Abstract
We developed an experimental platform for studying magnetic reconnection in an external magnetic field with simultaneous measurements of plasma imaging, flow velocity, and magnetic-field variation. Here, we investigate the stagnation and acceleration in counter-streaming plasmas generated by high-power laser beams. A plasma flow perpendicular to the initial flow directions is measured with laser Thomson scattering. The flow is, interestingly, accelerated toward the high-density region, which is opposite to the direction of the acceleration by pressure gradients. This acceleration is possibly interpreted by the interaction of two magnetic field loops initially generated by Biermann battery effect, resulting in a magnetic reconnection forming a single field loop and additional acceleration by a magnetic tension force., Comment: 6 pages, 4 figures, Physics of Plasmas, in press
- Published
- 2019
- Full Text
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23. Transition of dominant heating process from relativistic electron beam heating to thermal diffusion in an over picoseconds relativistic laser-solid interaction
- Author
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Natsumi Iwata, Takayoshi Sano, Yasuhiko Sentoku, Naoki Higashi, and Kunioki Mima
- Subjects
Nuclear and High Energy Physics ,Radiation ,Materials science ,Isochoric process ,Pulse duration ,Plasma ,Thermal diffusivity ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Physics::Plasma Physics ,law ,Picosecond ,0103 physical sciences ,Relativistic electron beam ,Atomic physics ,Diffusion (business) ,010306 general physics - Abstract
A mechanism of isochoric heating of a solid density plasma by a kilojoule (kJ) class laser with relativistic intensity and a ten picosecond (ps) pulse duration is delineated by collisional Particle-in-Cell (PIC) simulations. Before an emergence of kJ class lasers, plasma heating by the laser-accelerated relativistic electron beam (REB) has been studied as the dominant isochoric heating process by intense lasers. A recent experiment using a kJ class laser indicates that the thermal diffusion from the hot plasma surface becomes the dominant process of the isochoric heating in the ps scale laser irradiation. In this article, we demonstrate that a transition of the dominant isochoric heating process from the REB heating to the thermal diffusion happens in the 10 ps laser irradiation. The diffusion heat front propagates with the speed approximately 2 μm/ps in an Aluminum target. Additionally, the hot dense plasma expands to create a steep laser-plasma interface, which is found to reduce REB energy.
- Published
- 2020
24. Local plasma parameter measurements in colliding laser-produced plasmas for studying magnetic reconnection
- Author
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Tomihiko Kojima, Yasuhiro Kuramitsu, Takayoshi Sano, Taichi Morita, S. Kakuchi, K Aihara, M. Ota, Yoichi Sakawa, Y Nishioka, S. Sei, Masafumi Edamoto, Shuichi Matsukiyo, N. Ishizaka, M Takagi, Kunio Sakai, S. Egashira, Kentaro Tomita, Ryo Yamazaki, T Izumi, Shuta J. Tanaka, Y. Nakagawa, T. Minami, H. Murakami, K Sugiyama, and T Higuchi
- Subjects
Physics ,Nuclear and High Energy Physics ,Electron density ,Radiation ,Thomson scattering ,Magnetic reconnection ,Electron ,Plasma ,01 natural sciences ,010305 fluids & plasmas ,Ion ,Physics::Plasma Physics ,Physics::Space Physics ,0103 physical sciences ,Plasma parameter ,Electron temperature ,Atomic physics ,010306 general physics - Abstract
We have implemented laser Thomson scattering for local plasma measurement of electron and ion temperatures, electron density, flow velocity, and charge state. The electron density increases by two times in the interaction of two plasma flows, indicating collisionless interaction. The density and velocity show fluctuations only at t = 40 ns, and the density suddenly decreases, indicating the plasma ejection from the interaction region, which can be explained by a magnetic reconnection. The electron temperature in the double-flow is larger than that in the single flow. This may be explained by the energy transfer from the plasma kinetic energy to thermal energy. The ion temperature is much larger than electron temperature in the double-flow, and this may be explained by collisional effects between two plasmas, and/or possibly interpreted as a thermalization due to magnetic reconnection.
- Published
- 2020
25. PIC simulation for dense high Z plasma formation with ultrashort petawatt laser including radiation processes
- Author
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Naoki Higashi, K. Sugimoto, Atsushi Sunahara, Yasuhiko Sentoku, Takayoshi Sano, and N. Iwata
- Subjects
Nuclear and High Energy Physics ,Radiation ,Photon ,Materials science ,Physics::Optics ,Radiant energy ,Plasma ,Laser ,01 natural sciences ,010305 fluids & plasmas ,Ion ,law.invention ,Physics::Plasma Physics ,law ,Picosecond ,Physics::Space Physics ,0103 physical sciences ,Energy transformation ,Atomic physics ,010306 general physics - Abstract
Creation of hot dense highly charged plasma is key to realizing novel radiation sources, e.g., high Z ion beams and intense hard X-rays. We study the formation of dense silver plasma driven by an ultrashort petawatt laser using one-dimensional Particle-in-Cell (PIC) simulations take into account physics of collisional energy transport, ionizations, and radiations byproducts. For this purpose, we implemented the algorithm of radiation energy loss in hot plasmas enabling self-consistent PIC simulations of the silver plasma formation with radiation cooling. We demonstrated the highly charged silver plasma formation with a pressure of ~ 10 petapascal by irradiating a petawatt laser with peak intensity of 1021 W/cm2 in 30 femtoseconds. The energy stored in the hot silver plasma is released as hard X-rays photons in a few picosecond time scale with radiation intensity of 1017 W/cm2. The energy conversion from the laser to the emitted X-rays reaches ~ 10%.
- Published
- 2020
26. Two-color laser-plasma interactions for efficient production of non-thermal hot electrons
- Author
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N. Iwata, Hiroki Morita, Takayoshi Sano, K. Mima, S. Lee, King Fai Farley Law, R. Kodama, Yasunobu Arikawa, Daiki Kawahito, Hideo Nagatomo, Hiroshi Azechi, S. Sakata, Yasuhiko Sentoku, Keisuke Shigemori, Shinsuke Fujioka, and Kazuki Matsuo
- Subjects
Nuclear and High Energy Physics ,Radiation ,Materials science ,Phase (waves) ,Physics::Optics ,Electron ,Plasma ,Laser ,law.invention ,Wavelength ,law ,Excited state ,Thermal ,Energy transformation ,Physics::Atomic Physics ,Atomic physics - Abstract
Efficient production of non-thermal hot electrons has been demonstrated experimentally by interactions of a plasma and two-color lasers with wavelengths of 527 and 1053 nm. The two-color-lasers and plasma interactions caused a 4.8 times enhancement of the temperature of the hot electrons and a 2.7 times enhancement of energy conversion from the lasers to the hot electrons compared with that obtained with only a 527 nm laser. These experimental results can be explained by a staging electron acceleration mechanism realized with a mixture of plasma waves excited by the two-color lasers. The primary 527 nm laser excites at least two electron plasma waves. Those have completely different phase velocities, therefore, staging acceleration cannot occur only with the 527 nm laser. The secondary 1053 nm laser excites other electron plasma waves, of which the phase velocities locate between those of the waves excited by the primary 527 nm laser. Some of the background thermal electrons can be heated contentiously to several hundred kilo-electronvolts by the electron plasma waves excited by the two-color lasers.
- Published
- 2020
27. Flash X-ray backlight technique using a Fresnel phase zone plate for measuring interfacial instability
- Author
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Yasunobu Arikawa, Nicolai Philippe, Kazuki Ishigure, Huan Li, Chang Liu, Hideo Nagatomo, Takayoshi Sano, Shohei Sakata, Kazuki Matsuo, Natsuko Nagamatsu, Hiroki Kato, King Fai Farley Law, Hiroki Morita, Shinsuke Fujioka, Seung Ho Lee, Zhu Baojun, Youichi Sakawa, Guo Shuwang, Jo Nishibata, R. Takizawa, and Hiroshi Azechi
- Subjects
Nuclear and High Energy Physics ,Radiation ,Materials science ,business.industry ,Phase (waves) ,Plasma ,Shadowgraphy ,Zone plate ,Laser ,01 natural sciences ,Instability ,010305 fluids & plasmas ,law.invention ,Optics ,law ,Temporal resolution ,0103 physical sciences ,010306 general physics ,business ,Inertial confinement fusion - Abstract
Interfacial instabilities in high-energy-density plasmas are important topics in various research fields such as inertial confinement fusion, planetary sciences, and astrophysics. The growth of the instabilities can be examined in the laboratory by using high-power lasers coupled with high-resolution imaging technique. The resolutions both in space and time are essential for the observation of tiny and transient phenomena in high-energy-density plasmas. Here, the growth of a sinusoidal corrugation on the surface of a polystyrene foil during the laser-driven Richtmyer-Meshkov instability was measured by high-resolution X-ray shadowgraphy. In our experiment, a high-intensity short-pulse laser produced the X-ray flash that ensures a better temporal resolution. A Fresnel Phase Zone Plate was used for the improvement of spatial resolution, which realized an accuracy of 5.0 ± 1.0 µm in our system.
- Published
- 2020
28. Laboratory Observation of Radiative Shock Deceleration and Application to SN 1987A
- Author
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Bruno Albertazzi, Norimasa Ozaki, G. Rigon, Emeric Falize, P. Barroso, L. Van Box Som, M. Ota, Yoichi Sakawa, Th. Michel, Takayoshi Sano, F. Lefevre, C. Michaut, M. Koenig, S. Egashira, R. Kumar, P. Mabey, Laboratoire pour l'utilisation des lasers intenses (LULI), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS]Physics [physics] ,Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy and Astrophysics ,01 natural sciences ,Electromagnetic radiation ,Shock (mechanics) ,Computational physics ,Acceleration ,Supernova ,Space and Planetary Science ,0103 physical sciences ,Radiative transfer ,Laboratory observation ,010306 general physics ,010303 astronomy & astrophysics ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience; The first laboratory evidence of a radiative shock (RS) decelerating during its free expansion phase in an optically thick medium is presented. A shock is generated in a multilayer solid target under the irradiation of a high-power laser at the GEKKO XII laser facility. The rear surface of the target is connected to a gas cell filled with Xe. Upon breakout, an RS, characterized by low Boltzmann number Bo MUCH LESS-THAN 1 and Mihalas number R 10, is generated. Experimental results reveal that radiative losses through the radiative precursor cause the shock to lose energy and decelerate. A model is developed that describes the shock propagation as a function of time. The model is in agreement with both numerical simulations and experimental results. These results have tremendous consequences for astrophysical systems, such as SN 1987A, where radiative deceleration may play a role in the formation of the observed hotspots in the circumstellar ring.
- Published
- 2019
29. Plasma expansion accompanying superthermal electrons in over-picosecond relativistic laser-foil interactions
- Author
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Takayoshi Sano, Kunioki Mima, Yasuhiko Sentoku, and Natsumi Iwata
- Subjects
Materials science ,Nuclear Energy and Engineering ,Physics::Plasma Physics ,law ,Picosecond ,Physics::Space Physics ,Electron ,Plasma ,Atomic physics ,Condensed Matter Physics ,Laser ,FOIL method ,law.invention - Abstract
We study the plasma expansion dynamics in over-picosecond relativistic laser-foil interactions using one-dimensional particle-in-cell (PIC) simulations. A new expansion mode ‘isofield expansion’ appears after the well-known isothermal expansion due to the continuous energy input from the laser light to the plasma. The blowout of the heated plasma at the front surface triggers the transition from the isothermal mode to the new mode. In the new expansion mode, electrons and ions expand quasi-neutrally with a constant sheath electric field, and a large scale low density plasma is formed where superthermal electrons are produced efficiently. A two-dimensional PIC simulation confirms the appearance of the isofield expansion mode after the plasma blowout for a large focal spot laser.
- Published
- 2019
30. Turbulent hydrodynamics experiments in high energy density plasmas: scientific case and preliminary results of the TurboHEDP project
- Author
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Norimasa Ozaki, Alexis Casner, J. Ballet, G. Rigon, P. Mabey, D. Q. Lamb, Th. Michel, Takayoshi Sano, M. Koenig, Bruno Albertazzi, Tatiana Pikuz, Petros Tzeferacos, A. Faenov, Gianluca Gregori, Emeric Falize, and Youichi Sakawa
- Subjects
Physics ,Nuclear and High Energy Physics ,Field (physics) ,business.industry ,Turbulence ,Plasma ,Laser ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010305 fluids & plasmas ,Electronic, Optical and Magnetic Materials ,law.invention ,Nuclear Energy and Engineering ,law ,0103 physical sciences ,Radiative transfer ,Aerospace engineering ,National Ignition Facility ,business ,010303 astronomy & astrophysics ,Inertial confinement fusion ,Laser Mégajoule - Abstract
The physics of compressible turbulence in high energy density (HED) plasmas is an unchartered experimental area. Simulations of compressible and radiative flows relevant for astrophysics rely mainly on subscale parameters. Therefore, we plan to perform turbulent hydrodynamics experiments in HED plasmas (TurboHEDP) in order to improve our understanding of such important phenomena for interest in both communities: laser plasma physics and astrophysics. We will focus on the physics of supernovae remnants which are complex structures subject to fluid instabilities such as the Rayleigh–Taylor and Kelvin–Helmholtz instabilities. The advent of megajoule laser facilities, like the National Ignition Facility and the Laser Megajoule, creates novel opportunities in laboratory astrophysics, as it provides unique platforms to study turbulent mixing flows in HED plasmas. Indeed, the physics requires accelerating targets over larger distances and longer time periods than previously achieved. In a preparatory phase, scaling from experiments at lower laser energies is used to guarantee the performance of future MJ experiments. This subscale experiments allow us to develop experimental skills and numerical tools in this new field of research, and are stepping stones to achieve our objectives on larger laser facilities. We review first in this paper recent advances in high energy density experiments devoted to laboratory astrophysics. Then we describe the necessary steps forward to commission an experimental platform devoted to turbulent hydrodynamics on a megajoule laser facility. Recent novel experimental results acquired on LULI2000, as well as supporting radiative hydrodynamics simulations, are presented. Together with the development of LiF detectors as transformative X-ray diagnostics, these preliminary results are promising on the way to achieve micrometric spatial resolution in turbulent HED physics experiments in the near future.
- Published
- 2018
31. Magnetohydrodynamics of laser-produced high-energy-density plasma in a strong external magnetic field
- Author
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S. Lee, King Fai Farley Law, Hiroshi Azechi, Zhe Zhang, Takayoshi Sano, Shinsuke Fujioka, Yasunobu Arikawa, Shohei Sakata, Youichi Sakawa, Philippe Nicolai, Hideo Nagatomo, Yasuhiro Kuramitsu, Sadaoki Kojima, Kazuki Matsuo, and Taichi Morita
- Subjects
Materials science ,Condensed matter physics ,Gyroradius ,Atmospheric-pressure plasma ,Plasma ,Electron ,Thermal conduction ,01 natural sciences ,010305 fluids & plasmas ,Magnetic field ,Physics::Plasma Physics ,0103 physical sciences ,Magnetohydrodynamics ,010306 general physics ,Magnetosphere particle motion - Abstract
Recent progress in the generation in the laboratory of a strong ($g100$-T) magnetic field enables us to investigate experimentally unexplored magnetohydrodynamics phenomena of a high-energy-density plasma, which an external magnetic field of 200--300 T notably affects due to anisotropic thermal conduction, even when the magnetic field pressure is much lower than the plasma pressure. The external magnetic field reduces electron thermal conduction across the external magnetic field lines because the Larmor radius of the thermal electrons in the external magnetic field is much shorter than the mean free path of the thermal electrons. The velocity of a thin polystyrene foil driven by intense laser beams in the strong external magnetic field is faster than that in the absence of the external magnetic field. Growth of sinusoidal corrugation imposed initially on the laser-driven polystyrene surface is enhanced by the external magnetic field because the plasma pressure distribution becomes nonuniform due to the external magnetic-field structure modulated by the perturbed plasma flow ablated from the corrugated surface.
- Published
- 2017
32. Broadening of Cyclotron Resonance Conditions in the Relativistic Interaction of an Intense Laser with Overdense Plasmas
- Author
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Yuki Tanaka, Masakatsu Murakami, Natsumi Iwata, Masayasu Hata, Yasuhiko Sentoku, Takayoshi Sano, and Kunioki Mima
- Subjects
Electromagnetic field ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Field (physics) ,Field line ,Cyclotron ,Cyclotron resonance ,Resonance ,FOS: Physical sciences ,Plasma ,Laser ,01 natural sciences ,Physics - Plasma Physics ,010305 fluids & plasmas ,law.invention ,Plasma Physics (physics.plasm-ph) ,law ,Physics::Plasma Physics ,0103 physical sciences ,Physics::Space Physics ,Atomic physics ,Astrophysics - High Energy Astrophysical Phenomena ,010306 general physics - Abstract
The interaction of dense plasmas with an intense laser under a strong external magnetic field has been investigated. When the cyclotron frequency for the ambient magnetic field is higher than the laser frequency, the laser's electromagnetic field is converted to the whistler mode that propagates along the field line. Because of the nature of the whistler wave, the laser light penetrates into dense plasmas with no cutoff density, and produces superthermal electrons through cyclotron resonance. It is found that the cyclotron resonance absorption occurs effectively under the broadened conditions, or a wider range of the external field, which is caused by the presence of relativistic electrons accelerated by the laser field. The upper limit of the ambient field for the resonance increases in proportion to the square root of the relativistic laser intensity. The propagation of a large-amplitude whistler wave could raise the possibility for plasma heating and particle acceleration deep inside dense plasmas., Comment: 8 pages, 8 figures, accepted for publication in PRE
- Published
- 2017
- Full Text
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33. Production of sulphate-rich vapour during the Chicxulub impact and implications for ocean acidification
- Author
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Takafumi Matsui, Takeshi Watari, Sohsuke Ohno, Kosuke Kurosawa, K. Otani, Toshihiko Kadono, Yoichiro Hironaka, Tatsuhiro Sakaiya, Takayoshi Sano, Seiji Sugita, Taiga Hamura, and Keisuke Shigemori
- Subjects
inorganic chemicals ,biology ,Earth science ,digestive, oral, and skin physiology ,chemistry.chemical_element ,Ocean acidification ,biology.organism_classification ,Sulfur ,respiratory tract diseases ,Atmosphere ,Foraminifera ,chemistry.chemical_compound ,chemistry ,Environmental chemistry ,General Earth and Planetary Sciences ,Trioxide ,Geology - Abstract
Following the Chicxulub impact, many foraminifera in near-surface waters perished, but bottom-dwelling species survived. Impact experiments suggest that sulphate in Chicxulubs target rocks was released as predominantly sulphur trioxide, which would have been converted to sulphuric acid in the atmosphere and swept down swiftly by larger particles, acidifying the ocean surface.
- Published
- 2014
34. Electron acceleration in dense plasmas heated by a picosecond relativistic laser
- Author
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K. Mima, Yasuhiko Sentoku, Takayoshi Sano, and N. Iwata
- Subjects
Physics ,Nuclear and High Energy Physics ,Scattering ,Physics::Optics ,Plasma ,Electron ,Condensed Matter Physics ,Kinetic energy ,Laser ,Electromagnetic radiation ,law.invention ,Physics::Plasma Physics ,law ,Picosecond ,Physics::Atomic Physics ,Atomic physics ,Inertial confinement fusion - Abstract
Laser lights with relativistic intensities and pulse lengths exceeding the picosecond (ps) have been recently made available. Laser–plasma interactions with such a parameter regime belong to the mesoscale between kinetic and fluid regimes, and thus theories developed for sub-ps laser–plasma interactions are not straightforwardly applicable to those for the multi-ps regime. We here study the generation of high-energy electrons in ps relativistic laser–foil interactions by using the particle-in-cell (PIC) simulation. We show that the dynamics of the laser hole boring, which stops during over-ps laser irradiation, is a key to generate the high energy electrons. An energy distribution with a high-energy tail cannot be fitted by a single Maxwellian function, and is likely to be a nonthermal distribution through a stochastic interaction via the recirculation of electrons in the expanding foil plasma. The present study of superthermal electron generation can be a basis for ps laser applications such as fast ignition-based laser fusion, laser ion acceleration, and short-pulse x-ray generation.
- Published
- 2019
35. Dynamic X-ray diffraction observation of shocked solid iron up to 170 GPa
- Author
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Yoshihiko Kondo, Yuichi Inubushi, Guillaume Morard, Alessandra Benuzzi-Mounaix, Norimasa Ozaki, Gianluca Gregori, Jean-Michel Boudenne, David Riley, A. Denoeud, Ryosuke Kodama, Alessandra Ravasio, Takayoshi Sano, M. Makita, Hiroyuki Uranishi, Erik Brambrink, Maimouna Bocoum, François Guyot, Youichi Sakawa, Michel Koenig, Marion Harmand, Stephane Mazevet, Laboratoire pour l'utilisation des lasers intenses (LULI), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Diffraction ,Iron Phase Diagram ,010504 meteorology & atmospheric sciences ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,Astrophysics::High Energy Astrophysical Phenomena ,Analytical chemistry ,01 natural sciences ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,0103 physical sciences ,Earth Core ,010306 general physics ,0105 earth and related environmental sciences ,Phase diagram ,Multidisciplinary ,Chemistry ,Velocimetry ,Magnetic field ,Crystallography ,Volume (thermodynamics) ,13. Climate action ,X-ray crystallography ,Physical Sciences ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Terrestrial planet ,Crystallite ,laser compression - Abstract
International audience; Investigation of the iron phase diagram under high pressure and temperature is crucial for the determination of the composition of the cores of rocky planets and for better understanding the generation of planetary magnetic fields. Here we present X-ray diffraction results from laser-driven shock-compressed single-crystal and polycrystalline iron, indicating the presence of solid hexagonal close-packed iron up to pressure of at least 170 GPa along the principal Hugoniot, corresponding to a temperature of 4,150 K. This is confirmed by the agreement between the pressure obtained from the measurement of the iron volume in the sample and the inferred shock strength from velocimetry deductions. Results presented in this study are of the first importance regarding pure Fe phase diagram probed under dynamic compression and can be applied to study conditions that are relevant to Earth and super-Earth cores.
- Published
- 2016
36. Shock compression response of forsterite above 250 GPa
- Author
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Seiji Sugita, Kohei Miyanishi, Takayoshi Sano, Bruno Albertazzi, Ryosuke Kodama, Tomoaki Kimura, Toshimori Sekine, Norimasa Ozaki, Youichi Sakawa, Yuto Asaumi, Takafumi Matsui, and Yuya Sato
- Subjects
Shock wave ,Exothermic reaction ,Materials science ,010504 meteorology & atmospheric sciences ,MgO ,Mineralogy ,Thermodynamics ,engineering.material ,01 natural sciences ,Endothermic process ,Phase Transition ,law.invention ,Physical Phenomena ,law ,large rocky planets ,0103 physical sciences ,phase equilibria ,Pressure ,Crystallization ,010306 general physics ,Research Articles ,laser shock compression ,0105 earth and related environmental sciences ,incongruent crystallization ,Multidisciplinary ,Lasers ,Silicon Compounds ,SciAdv r-articles ,Forsterite ,Planetary system ,Hugoniot ,Shock (mechanics) ,Shock response spectrum ,engineering ,Planetary Science ,Research Article ,planetary impacts - Abstract
Shocked forsterite above 250 GPa indicates incongruent crystallization of MgO, its phase transition, and remelting., Forsterite (Mg2SiO4) is one of the major planetary materials, and its behavior under extreme conditions is important to understand the interior structure of large planets, such as super-Earths, and large-scale planetary impact events. Previous shock compression measurements of forsterite indicate that it may melt below 200 GPa, but these measurements did not go beyond 200 GPa. We report the shock response of forsterite above ~250 GPa, obtained using the laser shock wave technique. We simultaneously measured the Hugoniot and temperature of shocked forsterite and interpreted the results to suggest the following: (i) incongruent crystallization of MgO at 271 to 285 GPa, (ii) phase transition of MgO at 285 to 344 GPa, and (iii) remelting above ~470 to 500 GPa. These exothermic and endothermic reactions are seen to occur under extreme conditions of pressure and temperature. They indicate complex structural and chemical changes in the system MgO-SiO2 at extreme pressures and temperatures and will affect the way we understand the interior processes of large rocky planets as well as material transformation by impacts in the formation of planetary systems.
- Published
- 2016
37. Thomson scattering measurement of a collimated plasma jet generated by a high-power laser system
- Author
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Kiichiro Uchino, Toseo Moritaka, Akira Mizuta, Gianluca Gregori, Jiayong Zhong, Yuta Yamaura, C. Michaut, M. Koenig, Hideaki Takabe, A. Pelka, Kai Zhang, Youichi Sakawa, Shuichi Matsukiyo, R. Crowston, Yasuhiro Kuramitsu, Fudi Wang, Naofumi Ohnishi, Takayoshi Sano, Taichi Morita, T. Ishikawa, Dawei Yuan, Hugo Doyle, Nigel Woolsey, Kentaro Tomita, R. Shimoda, and Y. T. Li
- Subjects
History ,Drift velocity ,Thomson scattering ,Physics::Instrumentation and Detectors ,Astrophysics::High Energy Astrophysical Phenomena ,x-ray lasers ,Electron ,Collimated light ,Education ,law.invention ,Optics ,law ,Physics::Plasma Physics ,x-ray scattering ,Physics ,business.industry ,Plasma ,Laser ,Computer Science Applications ,hydrogen ,Physics::Space Physics ,Astrophysical plasma ,Electromagnetic electron wave ,High Energy Physics::Experiment ,Atomic physics ,business - Abstract
One of the important and interesting problems in astrophysics and plasma physics is collimation of plasma jets. The collimation mechanism, which causes a plasma flow to propagate a long distance, has not been understood in detail. We have been investigating a model experiment to simulate astrophysical plasma jets with an external magnetic field [Nishio et al., EPJ. Web of Conferences 59, 15005 (2013)]. The experiment was performed by using Gekko XII HIPER laser system at Institute of Laser Engineering, Osaka University. We shot CH plane targets (3 mm × 3 mm × 10 μm) and observed rear-side plasma flows. A collimated plasma flow or plasma jet was generated by separating focal spots of laser beams. In this report, we measured plasma jet structure without an external magnetic field with shadowgraphy, and simultaneously measured the local parameters of the plasma jet, i.e., electron density, electron and ion temperatures, charge state, and drift velocity, with collective Thomson scattering.
- Published
- 2016
38. Model experiment of magnetic field amplification in laser-produced plasmas via the Richtmyer-Meshkov instability
- Author
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Nigel Woolsey, Nicola Booth, J. N. Waugh, C. J. Barton, Akira Mizuta, Hideaki Takabe, H. Tanji, James Smallcombe, Toseo Moritaka, Takayoshi Sano, Gianluca Gregori, T. Sugiyama, R. Heathcote, C. D. Murphy, T. Ide, A. Dizière, Youichi Sakawa, Christopher D. Gregory, Yosuke Matsumoto, Naofumi Ohnishi, K. Nishio, M. Koenig, Shuichi Matsukiyo, Taichi Morita, and Yasuhiro Kuramitsu
- Subjects
Physics ,Shock wave ,Richtmyer–Meshkov instability ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics ,Plasma ,Condensed Matter Physics ,01 natural sciences ,Instability ,Computational physics ,Magnetic field ,Shock waves in astrophysics ,0103 physical sciences ,Radiative transfer ,Astrophysical plasma ,010306 general physics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
A model experiment of magnetic field amplification (MFA) via the Richtmyer-Meshkov instability (RMI) in supernova remnants (SNRs) was performed using a high-power laser. In order to account for very-fast acceleration of cosmic rays observed in SNRs, it is considered that the magnetic field has to be amplified by orders of magnitude from its background level. A possible mechanism for the MFA in SNRs is stretching and mixing of the magnetic field via the RMI when shock waves pass through dense molecular clouds in interstellar media. In order to model the astrophysical phenomenon in laboratories, there are three necessary factors for the RMI to be operative: a shock wave, an external magnetic field, and density inhomogeneity. By irradiating a double-foil target with several laser beams with focal spot displacement under influence of an external magnetic field, shock waves were excited and passed through the density inhomogeneity. Radiative hydrodynamic simulations show that the RMI evolves as the density inhomogeneity is shocked, resulting in higher MFA.
- Published
- 2016
39. Dynamic compression of dense oxide (Gd3Ga5O12) from 0.4 to 2.6 TPa: Universal Hugoniot of fluid metals
- Author
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Kohei Miyanishi, Norimasa Ozaki, Williams J. Nellis, Takayoshi Sano, Thanayut Kaewmaraya, Rajeev Ahuja, Ryosuke Kodama, Yoichi Sakawa, Tsutomu Mashimo, M. Knudson, Muhammad Ramzan, and T. Kimura
- Subjects
Multidisciplinary ,Materials science ,business.industry ,Oxide ,Mechanics ,Warm dense matter ,Fusion power ,Laser ,01 natural sciences ,Article ,010305 fluids & plasmas ,law.invention ,chemistry.chemical_compound ,Semiconductor ,chemistry ,law ,Physical Sciences ,0103 physical sciences ,Hypervelocity ,Fysik ,Current (fluid) ,010306 general physics ,business ,Line (formation) - Abstract
Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gd3Ga5O12 (GGG), were measured at extremely high pressures up to 2.6 TPa (26 Mbar) generated by high-power laser irradiation and magnetically-driven hypervelocity impacts. Above 0.75 TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallic conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. The systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions.
- Published
- 2016
40. Formation of density inhomogeneity in laser produced plasmas for a test bed of magnetic field amplification in supernova remnants
- Author
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Yoichi Sakawa, Christopher D. Gregory, T. Ide, J. N. Waugh, Taichi Morita, Takayoshi Sano, S. Dono, H. Tanji, Hideaki Takabe, Yasuhiro Kuramitsu, Nigel Woolsey, H. Aoki, Berenice Loupias, and M. Koenig
- Subjects
Shock wave ,Physics ,Electron density ,business.industry ,Astronomy and Astrophysics ,Cosmic ray ,Plasma ,Laser ,Magnetic field ,law.invention ,Interstellar medium ,Optics ,Space and Planetary Science ,law ,Magnetohydrodynamics ,business - Abstract
Density inhomogeneities for a test bed of magnetic field amplification in supernova remnants (SNRs) were created in laser produced plasmas. The density inhomogeneity is considered to be essential to the large magnetic field amplification to account for the very fast cosmic ray acceleration. In order to model the density variations about an order of magnitude in an interstellar medium, we performed three types of experiments using a high-power laser system: (1) irradiating a plastic (CH) plane with a single focal spot beams, (2) the same target with spatial separation of laser focal spots, and (3) irradiating a striped target of thin and thick CH plane. By irradiating a CH plane target with a single focal spot laser beams, a plasma plume was produced with the large density range. On the other hand, when the several laser beams with displacements of the focal spots, bumpy structures of electron density were produced. Making thin stripes on a CH plane target, density and velocity inhomogeneities were produced by irradiating the striped target with the laser beams. In the all methods the density variations were very large, which can be used for a model experiment of the magnetic field amplification.
- Published
- 2010
41. A new viscous instability in weakly ionised protoplanetary discs
- Author
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Anders Johansen, Takayoshi Sano, and Mariko Kato
- Subjects
Physics::Fluid Dynamics ,Physics ,Accretion disc ,Space and Planetary Science ,Turbulence ,Astronomy ,Astronomy and Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics ,Instability ,Accretion (astrophysics) - Abstract
Large regions of protoplanetary discs are believed to be too weakly ionised to support magnetorotational instabilities, because abundant tiny dust grains soak up free electrons and reduce the conductivity of the gas. At the outer edge of this “dead zone”, the ionisation fraction increases gradually and the resistivity drops until the magnetorotational instability can develop turbulence. We identify a new viscous instability which operates in the semi-turbulent transition region between “dead” and “alive” zones. The strength of the saturated turbulence depends strongly on the local resistivity in this transition region. A slight increase (decrease) in dust density leads to a slight increase (decrease) in resistivity and a slight decrease (increase) in turbulent viscosity. Such spatial variation in the turbulence strength causes a mass pile-up where the turbulence is weak, leading to a run-away process where turbulence is weakened and mass continues to pile up. The final result is the appearance of high-amplitude pressure bumps and deep pressure valleys. Here we present a local linear stability analysis of weakly ionised accretion discs and identify the linear instability responsible for the pressure bumps. A paper in preparation concerns numerical results which confirm and expand the existence of the linear instability.
- Published
- 2010
42. Hugoniot equation of state of Si-doped glow discharge polymer and scaling to other plastic ablators
- Author
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Norimasa Ozaki, G. Huser, Kohei Miyanishi, V. Recoules, R. Kodama, Takayoshi Sano, Youichi Sakawa, and P. Colin-Lalu
- Subjects
Physics ,Glow discharge ,Ab initio ,Condensed Matter Physics ,Laser ,01 natural sciences ,Dissociation (chemistry) ,010305 fluids & plasmas ,law.invention ,Physics::Fluid Dynamics ,Condensed Matter::Materials Science ,Physics::Plasma Physics ,law ,Ab initio quantum chemistry methods ,0103 physical sciences ,Compressibility ,Physics::Atomic Physics ,Atomic physics ,010306 general physics ,Inertial confinement fusion ,Scaling - Abstract
Pressure, density, and temperature were measured along the principal Hugoniot of the Si-doped Glow Discharge Polymer used in Inertial Confinement Fusion (ICF) capsules up to 5 Mbar, covering conditions beyond the first shock in a full-scale Inertial Confinement Fusion (ICF) capsule. The experiments were performed using the GEKKOXII laser at the Institute of Laser Engineering at Osaka University in Japan. Results are in good agreement with predictions obtained from ab initio Hugoniot calculations, but softer than the quotidian equation of state average atom model. Ab initio calculations show that dissociation of carbon bonds need to be taken into account in order to explain Hugoniot compressibility.
- Published
- 2018
43. DUST TRANSPORT IN PROTOSTELLAR DISKS THROUGH TURBULENCE AND SETTLING
- Author
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Takayoshi Sano, Neal J. Turner, and Augusto Carballido
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,Photosphere ,Turbulence ,FOS: Physical sciences ,Astronomy and Astrophysics ,Scale height ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Grain size ,T Tauri star ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Settling ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Magnetohydrodynamics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We apply ionization balance and MHD calculations to investigate whether magnetic activity moderated by recombination on dust can account for the mass accretion rates and the mid-infrared spectra and variability of protostellar disks. The MHD calculations use the stratified shearing-box approach and include grain settling and the feedback from the changing dust abundance on the resistivity of the gas. The two-decade spread in accretion rates among T Tauri stars is too large to result solely from variety in the grain size and stellar X-ray luminosity, but can be produced by varying these together with the disk magnetic flux. The diversity in the silicate bands can come from the coupling of grain settling to the distribution of the magneto-rotational turbulence, through three effects: (1) Recombination on grains yields a magnetically inactive dead zone extending above two scale heights, while turbulence in the magnetically active disk atmosphere overshoots the dead zone boundary by only about one scale height. (2) Grains deep in the dead zone oscillate vertically in waves driven by the turbulent layer above, but on average settle at the laminar rates, so the interior of the dead zone is a particle sink and the disk atmosphere becomes dust-depleted. (3) With sufficient depletion, the dead zone is thinner and mixing dredges grains off the midplane. The MHD results also show that the magnetic activity intermittently lifts clouds of dust into the atmosphere. The photosphere height changes by up to one-third over a few orbits, while the extinction along lines of sight grazing the disk surface varies by factors of two over times down to 0.1 orbit. We suggest that the changing shadows cast by the dust clouds on the outer disk are a cause of the daily to monthly mid-infrared variability in some young stars. (Abridged.), Comment: ApJ in press
- Published
- 2009
44. The Newest Technology of Extrusion Processing
- Author
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Takayoshi Sano, Akiyoshi Kobayashi, and Takehiro Yamamoto
- Subjects
Materials science ,Metallurgy ,Extrusion - Published
- 2009
45. Laser-Shock Compression of Liquid Hydrogen and Interior Structure of Jupiter
- Author
-
Norimasa Ozaki, Masahiro Ikoma, Takayoshi Sano, Tatsuhiro Sakaiya, and Keisuke Shigemori
- Subjects
Hydrogen ,Chemistry ,Gas giant ,chemistry.chemical_element ,Mineralogy ,General Chemistry ,Metallic hydrogen ,Condensed Matter Physics ,Molecular physics ,Shock (mechanics) ,Jupiter ,Condensed Matter::Materials Science ,Brightness temperature ,General Materials Science ,Physics::Atomic Physics ,Quartz ,Astrophysics::Galaxy Astrophysics ,Liquid hydrogen - Abstract
Hydrogen at high pressure in the fluid state is of great interest for understanding interiors of gas giant planets. We newly obtained Hugoniot data for liquid hydrogen up to 55 GPa under laser-driven shock loading using impedance matching to a quartz standard. The shocked temperature was determined simultaneously from the brightness temperature. The compression and temperature are almost consistent with theoretical models. High reflectivity of hydrogen was observed at 40 GPa, which suggests the fluid becomes conducting.
- Published
- 2009
46. On uncertainty of Jupiter's core mass due to observational errors
- Author
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Yasunori Hori, Masahiro Ikoma, Takayoshi Sano, and Shigeru Ida
- Subjects
Physics ,Jupiter ,Solar System ,Observational error ,Exploration of Jupiter ,Space and Planetary Science ,Gas giant ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Great conjunction ,Planetary mass ,Jupiter mass - Abstract
The origins of extrasolar gas giant planets have been discussed, based on our understanding of the gas giant planets in the solar system, Jupiter and Saturn. However, how Jupiter and Saturn formed is still uncertain because of the uncertainty in their interiors, especially the core mass (Mc). The uncertainty in Mc is partly due to those in observational data such as gravitational moments (J2n), equatorial radius (Req) and 1-bar temperatures (T1bar). New frontiers mission to Jupiter by NASA (JUNO) launched in 2011 is expected to reduce the observational errors. However, it is not necessarily clear yet which observational uncertainty dominates and how accurate observation is needed to constrain Mc enough to know the origin of Jupiter. Thus, modeling the interior of Jupiter, we evaluate each effect on Mc and required precision. We have found that the observational error of 5% in T1bar yields an error of several M⊕ in Mc. We have also found that the values of J6 of our successful models are confined in a narrow range compared to its observational error. This implies that comparison between the values of J6 of our successful models and the J6 value obtained from JUNO mission helps us to know whether the present theoretical model is valid.
- Published
- 2007
47. The Structure of Accretion Disks Formed by Merging of White Dwarfs
- Author
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Toru Tsuribe, Takayoshi Sano, Hideaki Takabe, and Toshinao Shioya
- Subjects
Physics ,Intermediate polar ,Future of an expanding universe ,Accretion disc ,Space and Planetary Science ,Astronomy ,White dwarf ,Astronomy and Astrophysics ,Massive compact halo object ,Blue dwarf ,Main sequence ,Black dwarf - Published
- 2007
48. The Effect of Neutrino Radiation on Magnetorotational Instability in Proto–Neutron Stars
- Author
-
Youhei Masada, Kazunari Shibata, and Takayoshi Sano
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Physics::Medical Physics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Momentum ,Neutron star ,Supernova ,Stars ,Space and Planetary Science ,Magnetorotational instability ,Astrophysics::Solar and Stellar Astrophysics ,Magnetohydrodynamics ,Neutrino ,Lepton - Abstract
Neutrino radiation takes a major role in the momentum, heat, and lepton transports in proto-neutron stars (PNSs). These diffusive processes affect the growth of magnetorotational instability (MRI) in PNSs. We perform a local linear analysis for the axisymmetric and nonaxisymmetric MRI including the effects of neutrino transports and ohmic dissipation. We find that the MRI can grow even in the multi-diffusive situations that are realized in neutrino loaded PNSs. When the toroidal magnetic component dominates over the poloidal one, nonaxisymmetric MRI modes grow much faster than axisymmetric modes. These results suggest the importance of the nonaxisymmetric MRI in PNSs. Thus the understandings of three-dimensional nonlinear evolutions of the MRI are necessary to reveal the explosion mechanism of core-collapse supernovae., Comment: Accepted for publication in ApJ, 24 pages,6 figures
- Published
- 2007
49. Experimental and ab initio investigations of microscopic properties of laser-shocked Ge-doped ablator
- Author
-
Norimasa Ozaki, Kohei Miyanishi, Ryosuke Kodama, Takayoshi Sano, Youichi Sakawa, G. Salin, V. Recoules, Bruno Albertazzi, and G. Huser
- Subjects
Physics ,Dopant ,Doping ,Ab initio ,chemistry.chemical_element ,Germanium ,Nanotechnology ,Molecular physics ,ABINIT ,Condensed Matter::Materials Science ,chemistry ,Atom ,Shocked quartz ,Inertial confinement fusion - Abstract
Plastic materials (CH) doped with mid-Z elements are used as ablators in inertial confinement fusion (ICF) capsules and in their surrogates. Hugoniot equation of state (EOS) and electronic properties of CH doped with germanium (at 2.5% and 13% dopant fractions) are investigated experimentally up to 7 Mbar using velocity and reflectivity measurements of shock fronts on the GEKKO laser at Osaka University. Reflectivity and temperature measurements were updated using a quartz standard. Shocked quartz reflectivity was measured at 532 and 1064 nm. Theoretical investigation of shock pressure and reflectivity was then carried out by ab initio simulations using the quantum molecular dynamics (QMD) code abinit and compared with tabulated average atom EOS models. We find that shock states calculated by QMD are in better agreement with experimental data than EOS models because of a more accurate description of ionic structure. We finally discuss electronic properties by comparing reflectivity data to a semiconductor gap closure model and to QMD simulations.
- Published
- 2015
50. Normal velocity freeze-out of the Richtmyer-Meshkov instability when a rarefaction is reflected
- Author
-
Takayoshi Sano and J. G. Wouchuk
- Subjects
Shock (fluid dynamics) ,Richtmyer–Meshkov instability ,Rarefaction ,Mechanics ,Instability ,Moving shock ,Physics::Fluid Dynamics ,symbols.namesake ,Classical mechanics ,Mach number ,symbols ,Refraction (sound) ,Oblique shock ,Mathematics - Abstract
The Richtmyer-Meshkov instability (RMI) develops when a shock front hits a rippled contact surface separating two different fluids. After the incident shock refraction, a transmitted shock is always formed and another shock or a rarefaction is reflected back. The pressure-entropy-vorticity fields generated by the rippled wave fronts are responsible for the generation of hydrodynamic perturbations in both fluids. In linear theory, the contact surface ripple reaches an asymptotic normal velocity which is dependent on the incident shock Mach number, fluids density ratio, and compressibilities. It was speculated in the past about the possibility of getting a zero value for the asymptotic normal velocity, a phenomenon that was called ``freeze-out'' [G. Fraley, Phys. Fluids 29, 376 (1986); K. Mikaelian, Phys. Fluids 6, 356 (1994), A. L. Velikovich et al., Phys. Plasmas 8, 592 (2001)]. In a previous paper, freeze-out was studied for the case when a shock is reflected at the contact surface [J. G. Wouchuk and K. Nishihara, Phys. Rev. E 70, 026305 (2004)]. In this work the freeze-out of the RMI is studied for the case in which a rarefaction is reflected back. Two different regimes are found: nearly equal preshock densities at the interface at any shock intensity, and very large density difference for strong shocks. The contour curves that relate shock Mach number and preshock density ratio are obtained in both regimes for fluids with equal and different compressibilities. An analysis of the temporal evolution of different cases of freeze-out is shown. It is seen that the freeze-out is the result of the interaction between the unstable interface and the rippled wave fronts. As a general and qualitative criterion to look for freeze-out situations, it is seen that a necessary condition for freeze-out is the same orientation for the tangential velocities generated at each side of the contact surface at $t=0+$. A comparison with the results of previous works is also shown.
- Published
- 2015
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