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ABSTRACT: Developments in measuring sound velocity of matter under ultrahigh pressure are described. We employed a time-resolved x-ray shadowgraph technique to measure the sound velocity of shock-compressed diamond and iron foils at around melt. The sound velocity significantly dropped at melting, a behavior that has been difficult to clarify by conventional measurements by subtracting particle velocity from shock velocity (u(s) - u(p)). In addition to sound velocity, other important parameters were also obtained simultaneously.
The Review of scientific instruments 10/2012; 83(10):10E529. · 1.52 Impact Factor
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S. Takasawa,
A. M. Nakamura, T. Kadono,
M. Arakawa,
K. Dohi,
S. Ohno,
Y. Seto,
M. Maeda,
K. Shigemori,
Y. Hironaka,
T. Sakaiya,
S. Fujioka,
T. Sano,
K. Otani,
T. Watari,
K. Sangen,
M. Setoh,
N. Machii,
and T. Takeuchi
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ABSTRACT: Fragments generated by high-velocity collisions between solid planetary bodies are one of the main sources of new interplanetary dust particles. However, only limited ranges of collision velocity, ejecta size, and target materials have been studied in previous laboratory experiments, and the collision condition that enables the production of dust-sized particles remains unclear. We conducted hypervelocity impact experiments on silicate rocks at relative velocities of 9 to 61 km s–1, which is beyond the upper limit of previous laboratory studies. Sub-millimeter-diameter aluminum and gold spheres were accelerated by laser ablation and were shot into dunite and basalt targets. We analyzed the surfaces of aerogel blocks deployed near the targets using an electron probe micro analyzer and counted the number of particles that contained the target material. The size distributions of ejecta ranged from five to tens of microns in diameter. The total cross-sectional area of dust-sized ejecta monotonically increased with the projectile kinetic energy, independent of impact velocity, projectile diameter, and projectile and target material compositions. The slopes of the cumulative ejecta-size distributions ranged from –2 to –5. Most of the slopes were steeper than the –2.5 or –2.7 that is expected for a collisional equilibrium distribution in a collision cascade with mass-independent or mass-dependent catastrophic disruption thresholds, respectively. This suggests that the steep dust size-distribution proposed for the debris disk around HD172555 (an A5V star) could be due to a hypervelocity collision.
The Astrophysical Journal Letters 05/2011; 733(2):L39. · 5.53 Impact Factor
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T. Sano,
N. Ozaki,
T. Sakaiya,
K. Shigemori,
M. Ikoma,
T. Kimura,
K. Miyanishi,
T. Endo,
A. Shiroshita,
H. Takahashi, [......],
Y. Hironaka,
A. Iwamoto, T. Kadono,
M. Nakai,
T. Okuchi,
K. Otani,
K. Shimizu,
T. Kondo,
R. Kodama,
K. Mima
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ABSTRACT: The principal Hugoniot for liquid hydrogen was obtained up to 55 GPa under laser-driven shock loading. The pressure and density of compressed hydrogen were determined by impedance matching to a quartz standard. The shock temperature was independently measured from the brightness of the shock front. Hugoniot data of hydrogen provide a good benchmark to modern theories of condensed matter. The initial number density of liquid hydrogen is lower than that for liquid deuterium, and this results in shock-compressed hydrogen having a higher compression and higher temperature than deuterium at the same shock pressure.
Phys. Rev. B. 01/2011; 83(5).
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T Sano,
N Ozaki,
T Sakaiya,
K Shigemori,
M Ikoma,
T Kimura,
K Miyanishi,
T Endo,
A Shiroshita,
H Takahashi, [......],
Y Hironaka,
A Iwamoto, T Kadono,
M Nakai,
T Okuchi,
K Otani,
K Shimizu,
T Kondo,
R Kodama,
K Mima
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ABSTRACT: Hydrogen at high pressure in the fluid state is of great interest for target design of inertial confinement fusion and understanding the interior structure of gas giant planets. In this work, we successfully obtained the 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 by the brightness temperature. The compression and temperature along the principal Hugoniot are in good agreement with theoretical models. High reflectivity of hydrogen was observed at 40 GPa, which suggests the fluid becomes conducting.
Journal of Physics Conference Series 09/2010; 244(4):042018.
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K. Otani,
K. Shigemori, T. Kadono,
Y. Hironaka,
M. Nakai,
H. Shiraga,
H. Azechi,
K. Mima,
N. Ozaki,
T. Kimura,
K. Miyanishi,
R. Kodama,
T. Sakaiya,
A. Sunahara
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ABSTRACT: This paper reports an experimental study on preheating of laser-irradiated targets. We performed temperature measurements at the rear surface of laser-irradiated targets under conditions of two different laser wavelengths (0.35 or 0.53 μm) and several intensities (2×1013–1×1014 W/cm2) in order to verify an effect of radiation and nonlocal electron heat transport. The preheating temperature was evaluated by observing self-emission, reflectivity, and expansion velocity at the rear surface of planar polyimide foils. The experimental results show that the x-ray radiation is dominant for preheating for 0.35-μm laser irradiation, but contribution of nonlocal electron heat transport is not negligible for 0.53-μm laser irradiation conditions.
Physics of Plasmas 03/2010; 17(3):032702-032702-6. · 2.15 Impact Factor
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Y. Hironaka,
K. Shigemori, T. Kadono,
S. Fujioka,
M. Tanabe,
A. Shiroshita,
N. Ozaki,
K. Miyanishi,
T. Kondo,
K. Otani,
T. Sakaiya,
K. Shimizu
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ABSTRACT: We performed wide angle x‐ray diffraction for Laser shocked MgO single crystal. Wide angle x‐ray diffraction technique was applied to measure the transient atomic motion near the Hugoniot elastic limit to determine the three dimensional atomic motion under shock loading. The perfect atomic uni‐axial motion was observed at the compression of 4.6%. This results was equivalent to the cubic‐tetragonal distortion within 5 ns.
AIP Conference Proceedings. 12/2009; 1195(1):607-610.
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N. Ozaki,
T. Sano,
M. Ikoma,
K. Shigemori,
T. Kimura,
K. Miyanishi,
T. Vinci,
F. H. Ree,
H. Azechi,
T. Endo, [......],
M. Nakai,
T. Norimatsu,
T. Okuchi,
K. Otani,
T. Sakaiya,
K. Shimizu,
A. Shiroshita,
A. Sunahara,
H. Takahashi,
R. Kodama
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ABSTRACT: Equation-of-state data, not only pressure and density but also temperature, for polystyrene (CH) are obtained up to 510 GPa. The region investigated in this work corresponds to an intermediate region, bridging a large gap between available gas-gun data below 60 GPa and laser shock data above 500 GPa. The Hugoniot parameters and shock temperature were simultaneously determined by using optical velocimeters and pyrometers as the diagnostic tools and the α-quartz as a new standard material. The CH Hugoniot obtained tends to become stiffer than a semiempirical chemical theoretical model predictions at ultrahigh pressures but is consistent with other models and available experimental data.
Physics of Plasmas 06/2009; 16(6):062702-062702-6. · 2.15 Impact Factor
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H Takabe,
T N Kato,
Y Sakawa,
Y Kuramitsu,
T Morita, T Kadono,
K Shigemori,
K Otani,
H Nagatomo,
T Norimatsu, [......],
W-H Zhang,
X Hu,
S-Y Liu,
Y K Ding,
L Zhang,
Y-J Tang,
B-H Zhang,
Z-J Zheng,
Z-M Sheng,
J Zhang
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ABSTRACT: We propose that most of the collisionless shocks in the Universe, for example, supernova remnant shocks, are produced because of the magnetic field generated by Weibel instability and its nonlinear process. In order to verify and validate the computational result confirming this theory, we are carrying out model experiments with intense lasers. We are going to make a collisionless counter-streaming plasma with intense laser ablation based on the scaling law to laser plasma with the particle-in-cell simulation resulting in Weibel-mediated shock formation. Preliminary experimental data are shown. The photo-ionization and resultant non-LTE plasma physics are also very important subjects in astrophysics related to mainly compact objects, for example, black hole, neutron star and white dwarf. Planckian radiation with its temperature 80–100 eV has been produced in gold cavity with irradiation of intense lasers inside the cavity. The sample materials are irradiated by the radiation inside the cavity and absorption and self-emission spectra are observed and analyzed theoretically. It is demonstrated how the effect of non-LTE is essential to reproduce the experimental spectra with the use of a precision computational code.
Plasma Physics and Controlled Fusion 11/2008; 50(12):124057. · 2.42 Impact Factor
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K Shigemori,
K Shimizu,
Y Nakamoto,
T Irifune,
H Sumiya,
N Ozaki,
R Kodama,
K Otani,
D Ichinose,
Y Hironaka, T Kadono,
H Azechi,
K Mima,
J Wark,
B Remington
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ABSTRACT: Experiments on shock compression of diamond foils with intense laser are reported. In order to explore high-pressure and low-temperature region of the carbon phase-diagram, we irradiate single-crystal (Type-Ib) crystal foils with a shaped (ramp) pulse at the pressure of over 1TPa. We observed time-resolved reflectivity from the rear surface of the diamond during the shock compression with velocity interferometer system for any reflector (VISAR). Simultaneous observation of optical measurements and x-ray diffraction has been tested. Preliminary results on decompression of the diamond crystal due to x-ray heating were observed.
Journal of Physics Conference Series 06/2008; 112(4):042023.
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M Murakami,
H. Azechi,
H Nagatomo, T. Kadono,
K Shigemori,
Y. Hironaka,
T Watari,
K Takeda,
T. Norimatsu,
H Shiraga,
K. Mima,
S. Obenschain,
M Karasik,
J. Bates,
D. Colombant,
Y Aglitskiy,
A. Velikovich,
A. Schmitt,
J. Sethian
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ABSTRACT: First integrated experiments for impact ignition have been performed, in which a fraction of separately accelerated deuterated polystyrene (CD) shell (the impactor) at around 600 km s^-1 was collided with another fraction of pre-compressed CD fuel. The kinetic energies of the impactor were observed to be converted into thermal energy corresponding to temperatures of about 1.6 keV. We have observed as a result an increase of two orders of magnitude in neutron yield at the right timing of the impact collision, demonstrating the high potential of impact ignition for fusion energy production.
