Faculty Profiles - Nakai Mitsuo

Papers - Nakai Mitsuo

Division display 261 - 280 of about 304 ／ All the affair displays >>

CRYOGENIC DEUTERIUM TARGET EXPERIMENTS WITH THE GEKKO-XII, GREEN LASER SYSTEM

KA TANAKA, T YAMANAKA, K NISHIHARA, T NORIMATSU, N MIYANAGA, H SHIRAGA, M NAKAI, Y KITAGAWA, R KODAMA, T KANABE, H AZECHI, M HEYA, T JITSUNO, M KADO, K MIMA, M NAKATSUKA, A NISHIGUCHI, H TAKABE, M TAKAGI, K TSUBAKIMOTO, M TSUKAMOTO, Y KATO, Y IZAWA, S NAKAI

PHYSICS OF PLASMAS 2 ( 6 ) 2495 - 2503 1995.6

DYNAMIC BEHAVIOR OF RIPPLED SHOCK-WAVES AND SUBSEQUENTLY INDUCED AREAL-DENSITY-PERTURBATION GROWTH IN LASER-IRRADIATED FOILS

T ENDO, K SHIGEMORI, H AZECHI, A NISHIGUCHI, K MIMA, M SATO, M NAKAI, S NAKAJI, N MIYANAGA, S MATSUOKA, A ANDO, KA TANAKA, S NAKAI

PHYSICAL REVIEW LETTERS 74 ( 18 ) 3608 - 3611 1995.5

STIMULATED RAMAN-SCATTERING FROM SYMMETRICALLY ILLUMINATED 2-LAYERED SPHERICAL TARGETS WITH 527-NM LASER LIGHT Reviewed

M TSUKAMOTO, KA TANAKA, K MIMA, M KADO, S MIYAMOTO, M NAKAI, T NORIMATSU, M TAKAGI, K NISHIHARA, T YAMANAKA, S NAKAI, A NISHIGUCHI

PHYSICS OF PLASMAS 2 ( 2 ) 486 - 492 1995.2

Erratum: Dynamic behavior of rippled shock waves and subsequently induced areal-density-perturbation growth in laser-irradiated foils (Physical Review Letters (1995) 75, 15) Reviewed

Endo T, Shigemori K, Azechi H, Nishiguchi A, Mima K, Sato M, Nakai M, Nakaji S, Miyanaga N, Matsuoka S, Ando A, Tanaka K.A, Nakai S

Physical Review Letters 75 ( 15 ) 1995

HIGH HARMONIC-GENERATION WITH A CPA KRF LASER Reviewed

M ZEPF, W BLYTH, MH KEY, M NAKAI, SG PRESTON, JS WARK

LASER INTERACTION WITH MATTER ( 140 ) 467 - 470 1995

High harmonics have been observed from a 0.8 TW, 350-fs KrF CPA laser focused to 8 x 10(17) W cm(-2) in gas jet targets. Estimates of the absolute conversion efficiencies have been made. The efficiency and relative strength of the harmonics was found to be largely independent of the position of the laser focus within the gas jet, and of the density, suggesting a coherence length limited by dephasing effects due to plasma electrons. The highest harmonics are attributed to ions rather than neutrals.

IMPLOSION EXPERIMENTS OF CRYOGENICALLY COOLED TARGETS Reviewed

T YAMANAKA, KA TANAKA, K NISHIHARA, T NORIMATSU, H SHIRAGA, Y KITAGAWA, N MIYANAGA, H AZECHI, H NISHIMURA, M NAKAI, R KODAMA, M HEYA, M TAKAGI, Y IZAWA, T KANABE, T JITSUNO, M NAKATSUKA, K MIMA, M MURAKAMI, S NAKAI, T ENDO, C YAMANAKA

LASER INTERACTION WITH MATTER ( 140 ) 25 - 28 1995

Cryogenically cooled deuterium targets with plastic ablator are imploded as well as plastic targets with deuterium gas at laser intensities of 4-5x10(14) W/cm(2) and 1-2x10(14) W/cm(2). The low intensity shots showed neutron yields normalized by 1-D simulation to be one tenth up to convergence ratio of 30, while those at the high intensity are one hundredth. The observed neutron yields and density radius product rho Rs are respectively 10(8) and 8 mg/cm(2) for cryogenic liquid targets. 2-D x-ray images obtained with a 10 ps temporal resolution camera reveal previously undiscovered information of imploding core plasmas.

Observation of Raman light in expanding plasmas from two-layered spherical targets irradiated with 527 nm laser

M. Tsukamoto, K. A. Tanaka, K. Mima, M. Kado, S. Miyamoto, M. Nakai, T. Norimatsu, M. Takagi, K. Nishihara, T. Yamanaka, S. Nakai

1994.10

RECENT PROGRESS IN LASER FUSION-RESEARCH AT OSAKA-UNIVERSITY - UNIFORMITY AND STABILITY ISSUES

K NISHIHARA, M MURAKAMI, H AZECHI, T JITSUNO, T KANABE, M KATAYAMA, N MIYANAGA, M NAKAI, M NAKATSUKA, K TSUBAKIMOTO, S NAKAI

PHYSICS OF PLASMAS 1 ( 5 ) 1653 - 1661 1994.5

Improvement of laser irradiation uniformity in the Gekko XII system [IEEE J. Quantum Electron. QE-17, 1639 (1981)], both single beam pattern and power balance, is discussed. Substantial reduction of laser absorption nonuniformity is obtained for spherical harmonic modes greater than 15 by introducing spectrally dispersed amplified spontaneous emission. No perturbation growth is observed in flat foils accelerated by spectrally dispersed amplified spontaneous emission. Dependences of laser absorption uniformity on beam pattern and power imbalance are investigated in detail. The design goal of the power imbalance in the precision Gekko XII system is 3% in peak to valley, and laser absorption nonuniformity is estimated to be a few percent. Growth of hydrodynamic instabilities is analyzed for high convergence ratio implosions in the precision Gekko XII system.

IMPLOSION OF D-2 TEMPERATURE-CONTROLLED CRYOGENIC FOAM TARGETS WITH PLASTIC ABLATORS

A RICHARD, KA TANAKA, K NISHIHARA, M NAKAI, M KATAYAMA, YO FUKUDA, T KANABE, Y KITAGAWA, T NORIMATSU, M NAKATSUKA, T YAMANAKA, M KADO, T KAWASHIMA, C CHEN, M TSUKAMOTO, S NAKAI

PHYSICAL REVIEW E 49 ( 2 ) 1520 - 1526 1994.2

The implosion hydrodynamics of temperature-controlled cryogenic deuterium foam targets with plastic ablators is investigated. The experimental data recorded with x-ray imaging systems are compared to a one-dimensional (1D) simulation. The ablation front trajectories derived from x-ray streak-camera data agree with 1D simulation. However, an x-ray core emission is observed at an earlier time, and for a longer duration than that predicted. For the three liquid-fuel shots, the convergence ratios are, respectively, 0.4, 0.9, and 0.7 times that predicted by the ID simulation.

4.8-KEV X-RAY BACKLIGHT FRAMING METHOD FOR OBSERVING IMAGES OF SOFT-X-RAY-DRIVEN FUSION CAPSULES

M KATAYAMA, H SHIRAGA, M NAKAI, T KOBAYASHI, Y KATO

REVIEW OF SCIENTIFIC INSTRUMENTS 64 ( 3 ) 706 - 710 1993.3

We report on a diagnostic method for observing the implosion asymmetry of soft-x-ray-driven fusion capsules. The method consists of an x-ray backlight source using a 4.8-keV quasi-monochromatic titanium x-ray source and a fast multiframe x-ray imaging system. With the proper combination of spectral filters and photocathode to reduce intense background x rays from a gold cavity plasma, x-ray backlighting images of the fusion capsules have been successively obtained with spatial and temporal resolutions of 20 mum and 80 ps, respectively. These images are used to study the implosion velocity and the lower-mode distortion caused by x-ray irradiation nonuniformity on the imploding fusion capsule.

IMPLOSION EXPERIMENTS INVOLVING CRYOGENIC FOAM TARGETS WITH PLASTIC ABLATOR

T YAMANAKA, K NISHIHARA, KA TANAKA, T NORIMATSU, Y KITAGAWA, M NAKAI, M TAKAGI, A RICHARD, M KATAYAMA, C CHEN, M KADO, M TSUKAMOTO, T JITSUNO, R KODAMA, H AZECHI, N MIYANAGA, K MIMA, M NAKATSUKA, S NAKAI, T KANABE, M MURAKAMI, A NISHIGUCHI, C YAMANAKA

PLASMA PHYSICS AND CONTROLLED NUCLEAR FUSION RESEARCH 1992, VOL 3 pp 151-158 151 - 158 1993

PHYSICS HIGHLIGHTS OF THE GEKKO12-PROGRAM Reviewed

K MIMA, S NAKAI, H AZECHI, A NISHIGUCHI, H TAKABE, N MIYANAGA, H NAKANO, M NAKAI, M KATAYAMA, K NISHIHARA, N NAKATSUKA, T JITSUNO, K TANAKA, H NISHIMURA, H SHIRAGA, T ENDO, T YAMANAKA, Y KATO, C YAMANAKA

PLASMA PHYSICS AND CONTROLLED FUSION 34 ( 13 ) 1775 - 1783 1992.12

Recently, hollow shell pellets have been imploded uniformly by the Gekko 1 2 laser system to be compressed to several hundreds g/cm3. The compressed density has been measured both by the neutron activation methods and the electron degeneracy measurement. The densities given by the above two methods are consistent.
The target parameter dependences of the density are analyzed with die one climensional implosion simulation code. Except the case of high convergence ratio implosion, the compressed plasma density obtained by the simulation code with nonlocal heat transport and/or high energy electron preheating agrees with the experimental results. As for the high convergence implosion, the one dimensional simulation does not give good prediction of the implosion, in particular for the neutron yield. Actually, the experimental neutron yield for the convergence ratio higher than 20 is lower by more than two orders of magnitude than the simulation value.
The preheating and stability are the key physics for die high density compression. As for the preheating, it turns out that the two plasmon decay plays an important role in the accelerated shell preheating. As for the stability, the initial target surface roughness and the laser irradiation non-uniformity are carefully checked. By the theoretical stability analysis, the stability of the high density compression is found to be marginal. Therefore, we are afraid that the neutron yield may degradate by the hot-cold plasma mixing. The details of the Rayleigh-Taylor instability analysis and experiments are discussed in the text.

Generation of Stimulated Raman Scattering from Two-layerd Spherical Target Excited by 527nm-laser

TSUKAMOTO Masahiro

68 91 - 101 1992.11

COMPRESSION EXPERIMENTS AND PROSPECTS OF THERMONUCLEAR REACTION IGNITION ON GEKKO-XII INSTALLATION UNDER LTF PROGRAM Reviewed

S NAKAI, K MIMA, K AZECHI, N MIYANAGA, A NISHIGUCHI, T YAMANAKA, K NISHIKHARA, KA TANAKA, M NAKAI, R KODAMA, M KATAYAMA, M KADO, M TSUKOMOTO, KATO, I, K NISHIMURA, K SHIRAGA, T ENDO, M NAKATSUKA, T SASAKI, T YUTSUNO, K IOSHIDA, T KANABE, K NAKANO, M YAMANAKA, K NAITO, T NORIMATSU, M TAKAGI, T CHEN, Y IZAVA, S YAMANAKA

KVANTOVAYA ELEKTRONIKA 19 ( 10 ) 947 - 974 1992.10

Experimental results on high density compression of thermonuclear fuel on Gekko-XII installation are reported. The density of the compressed matter is up to 600 times high than the solid state density, rhoR parameter being 0.51 +/- 0.14 g/cm2. Prospects of going from the compression experiments to thermonuclear reaction ignition and high gain are studied numerically. A deeper insight into the processes occurring in the target cavity with indirect compression has been gained.

LASER FUSION - HIGH-DENSITY COMPRESSION EXPERIMENT AND IGNITION PROGRAM WITH GEKKO-XII Reviewed

S NAKAI, K MIMA, H AZECHI, N MIYANAGA, A NISHIGUCHI, T YAMANAKA, K NISHIHARA, KA TANAKA, M NAKAI, R KODAMA, M KATAYAMA, M KADO, M TSUKAMOTO, Y KATO, H TAKABE, H NISHIMURA, H SHIRAGA, T ENDO, M NAKATSUKA, T SASAKI, T JITSUNO, K YOSHIDA, T KANABE, H NAKANO, K TSUBAKIMOTO, M YAMANAKA, K NAITO, T NORIMATSU, M TAKAGI, T CHEN, Y IZAWA, C YAMANAKA

LASER INTERACTION AND RELATED PLASMA PHENOMENA, VOL 10 10 443 - 502 1992

TIME-RESOLVED MEASUREMENTS OF LASER-INDUCED SHOCK-WAVES IN DEUTERATED POLYSTYRENE POROUS TARGETS BY X-RAY BACKLIGHTING

R KODAMA, KA TANAKA, M NAKAI, K NISHIHARA, T NORIMATSU, T YAMANAKA, S NAKAI

PHYSICS OF FLUIDS B-PLASMA PHYSICS 3 ( 3 ) 735 - 744 1991.3

Experimental studies are presented of laser-driven shock waves in deuterated polystyrene porous targets observed with x-ray streak shadowgraphy. Using two different target-mass densities of 0.1 g/cm3 and 0.2 g/cm3, the density dependence of the shock velocity was obtained as upsilon-s proportional-rho-0.45 +/- 0.02 and agreed well with a simple scaling obtained from the Hugoniot relation. X-ray shadowgraphy has shown a shock formation in porous targets and analysis suggests that there are two parts to compression waves: a shock front and a following pileup zone of multiple shock waves. Temporal histories of the pressure, the temperature, and the compression were estimated from the measured shock velocities and the opacities. It was found that the pressure peak due to the shock front was retarded to that by the pileup zone. The pileup zone had a higher compression and followed a thermodynamic condition closer to an adiabat than the shock front.

MULTIFRAME X-RAY-IMAGING SYSTEM FOR TEMPORALLY AND SPATIALLY RESOLVED MEASUREMENTS OF IMPLODING INERTIAL CONFINEMENT FUSION-TARGETS

M KATAYAMA, M NAKAI, T YAMANAKA, Y IZAWA, S NAKAI

REVIEW OF SCIENTIFIC INSTRUMENTS 62 ( 1 ) 124 - 129 1991.1

A compact and simple multiframe x-ray imaging system was developed in order to monitor the implosion of spherical targets in inertial confinement fusion research. Time intervals between consecutive frames can be adjusted flexibly, and the maximum number of adjacent frames is 20 for an overall duration of 1.4 ns. Each frame is recorded with a temporal resolution of 83 +/- 20 ps, a spatial resolution of 10 lp/mm at a modulation transfer function of 20%, and an intensity dynamic range of 10(3). A proximity focused image intensifier with two microchannel plates allows to obtain a gain of 10(5). Measured temporal response and gain characteristics could be reproduced by a simple Monte Carlo calculation.

ANNEALING OF POLYSTYRENE MICROCAPSULES FOR INERTIAL CONFINEMENT FUSION EXPERIMENTS Reviewed

S KOBAYASHI, T NORIMATSU, M NAKAI, KA TANAKA, T YAMANAKA, S NAKAI, K ITO

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS 9 ( 1 ) 150 - 153 1991.1

HIGH-DENSITY COMPRESSION EXPERIMENTS AT ILE, OSAKA Reviewed

H AZECHI, T JITSUNO, T KANABE, M KATAYAMA, K MIMA, N MIYANAGA, M NAKAI, S NAKAI, H NAKAISHI, M NAKATSUKA, A NISHIGUCHI, PA NORRAYS, Y SETSUHARA, M TAKAGI, M YAMANAKA

LASER AND PARTICLE BEAMS 9 ( 2 ) 193 - 207 1991

Direct-drive implosion experiments on the GEKKO XII laser (9 kJ, 0.5-mu-m, 2 ns) with deuterium and tritium (DT) exchanged plastic hollow shell targets demonstrated fuel areal densities (rho-R) of approximately 0.1 g/cm2 and fuel densities of approximately 600 times liquid density at fuel temperatures of approximately 0.3 keV. (The density and rho-R values refer only to DT and do not include carbons in the plastic targets.) These values are to be compared with thermonuclear ignition conditions, i.e. fuel densities of 500-1000 times liquid density, fuel areal densities greater than 0.3 g/cm2, and fuel temperatures greater than 5 keV. The irradiation nonuniformity in these experiments was significantly reduced to a level of < 5% in root mean square by introducing random-phase plates. The target irregularity was controlled to a 1% level. The fuel rho-R was directly measured with the neutron activation of Si, which was originally compounded in the plastic targets. The fuel densities were estimated from the rho-R values using the mass conservation relation, where the ablated mass was separately measured using the time-dependent X-ray emission from multilayer targets. Although the observed densities were in agreement with one-dimensional calculation results with convergence ratios of 25-30, the observed neutron yields were significantly lower than those of the calculations. This suggests the implosion uniformity is not sufficient to create a hot spark in which most neutrons should be generated.

HIGH-DENSITY COMPRESSION OF HOLLOW-SHELL TARGET BY GEKKO XII AND LASER FUSION-RESEARCH AT ILE, OSAKA-UNIVERSITY Reviewed

S NAKAI, K MIMA, M YAMANAKA, H AZECHI, N MIYANAGA, A NISHIGUCHI, H NAKAISHI, YW CHEN, Y SETSUHARA, PA NORREYS, T YAMANAKA, K NISHIHARA, KA TANAKA, M NAKAI, R KODAMA, M KATAYAMA, Y KATO, H TAKABE, H NISHIMURA, H SHIRAGA, T ENDO, K KONDO, M NAKATSUKA, T SASAKI, T JITSUNO, K YOSHIDA, T KANABE, A YOKOTANI, T NORIMATSU, M TAKAGI, H KATAYAMA, Y IZAWA, C YAMANAKA

LASER INTERACTION AND RELATED PLASMA PHENOMENA, VOL 9 9 25 - 67 1991

　 PREV - NEXT 　

<Nakai Mitsuo>

Papers - Nakai Mitsuo