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  • Articles: DFG German National Licenses  (89)
  • 1995-1999  (66)
  • 1985-1989  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Recent progress of implosion experiments with uniformity-improved GEKKO XII laser facility at the Institute of Laser Engineering, Osaka University (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2077-2083 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The irradiation uniformity of the GEKKO XII laser [C. Yamanaka et al., IEEE J. Quantum Electron. QE-17 1639 (1981)] has been improved by using partially coherent light with angular spectral dispersion and by improving power balance among the beams. Implosion experiments with the uniformity-improved GEKKO XII have been carried out in order to demonstrate stable formation of the hot spark. The isentrope of the compressed pellet shell is controlled by adding a prepulse to enhance the ablative stabilization of the Rayleigh–Taylor instability. The implosion dynamics has been investigated by x-ray imaging and neutron diagnostics. The experimental results are compared with the mix model prediction based on the one-dimensional hydrodynamic simulation. The degradation of neutron yield is attributed to the low-mode asymmetry. Finally, recent results of planer target experiments on the ablative stabilization of the Rayleigh–Taylor instability are also presented. The observed linear growth rate was about 50% of the classical growth rate and was lower than that of the theoretical prediction, based on the Takabe formula combined with the one-dimensional simulation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872005
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  • 2
    Electronic Resource
    Electronic Resource
    Study of indirectly driven implosion by x-ray spectroscopic measurements (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2063-2074 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fusion pellet implosion by laser-generated x rays was investigated by means of time-integrated spectroscopic measurements. Deuterium fuel was seeded with a small amount of Ar in order to determine the electron temperature and the density of the compressed fuel from, respectively, the emission intensity ratio and the broadening of the Lyβ (Ar17+1s-3p) and Heβ (Ar16+1s2-1s3p) lines. Comparison of the observed results with volume-averaged temperatures and densities obtained from one-dimensional (1-D) fluid-dynamic simulations showed large discrepancies at maximum compression. One possible explanation is that the fuel is stably compressed until the beginning of pusher deceleration by collision with a reflected shock wave from the pellet center, and that further compression during the deceleration phase is terminated in particular for heavy stagnation cases. Similar results were obtained for fusion output. Experimentally obtained neutron yields were close to those from the 1-D simulations at the beginning of the deceleration but a factor of 10–100 less than those expected at maximum compression. These results were examined in terms of shell disintegration in the acceleration phase and pusher–fuel mixing at the contact surface in the deceleration phase due to growth of initial perturbations of the pellet resulting from fluid instabilities. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871293
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  • 3
    Electronic Resource
    Electronic Resource
    Development of a two-dimensional space-resolved high speed sampling camera : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 625-628 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We developed a two-dimensional spatial resolved high-speed UV sampling camera (HISAC) to study energy transport in laser-produced plasmas. The HISAC is composed of an optical bundle of fibers coupled to a streak camera to obtain a two-dimensional spatial resolution with a temporal resolution of less than a few 10 ps. This HISAC system was demonstrated in the experiments on inferred uniformity measurements of laser-ablation pressures as well as on energy transport in ultraintense laser-plasma interactions. Two-dimensional shock heating was temporally resolved in a hemispherical target, resulting in the distribution of the ablation pressure as a function of laser incidence angle. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149383
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced production of multicharged boron ions by approaching a boride target to an ECR zone : Proceedings of the 6th international conference on ion sources (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1177-1179 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Multicharged boron ions have been produced by a sputtering boride target in a 2.45-GHz electron cyclotron resonance (ECR) source. The target material is immersed in an ECR argon plasma along the geometrical axis of the mirror field, and dc bias voltages are applied. Extracted boron ion currents increase as the target approaches the ECR zone formed at the bottom of mirror trap although the argon charge state deteriorates. The increase of boron ion current is coincident with that of the solid angle subtended by the target at the ECR zone. Measurement of the boron flux shows that the increase of boron atoms sputtered into the ECR zone causes this enhanced production. Ratio of total boron to argon ion current and that of B2+ to B+ current are about 10% and 10%–20%, respectively. The B3+ current can be detected at low microwave power (∼150 W). The isotopes of boron are clearly separated in natural abundance ratio. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146724
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  • 5
    Electronic Resource
    Electronic Resource
    Formation of rectilinearly wide plasmas by a slotted waveguide under electron cyclotron resonance : Proceedings of the 6th international conference on ion sources (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 997-999 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A plasma source was developed for ion implanters capable of irradiating large-area substrates. Microwave discharge is performed by electron cyclotron resonance (ECR). A rectilinearly wide flux of magnetic induction is formed with two long permanent magnets with oppositely facing poles. The ECR zone formed inside a vacuum chamber is elongated in the direction along the pole faces. A waveguide slotted along its E plane is inserted between the magnets. The long slot radiates microwaves into the vacuum chamber through dielectric materials. These materials play the role of waveguide. Plasmas are uniformly generated in the direction along the slotted waveguide when it is terminated with a short plunger. This mechanism is analyzed by calculating radiation patterns of the slotted waveguide. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146654
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  • 6
    Electronic Resource
    Electronic Resource
    Two-dimensional toroidal electron analyzer for energy and angular dispersive measurements (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1970-1977 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A toroidal electrostatic analyzer with a two-dimensional position-sensitive electron detector has been developed for the measurement of differential excitation cross sections in electron-ion collisions. The electron position is resolved simultaneously in the energy and angular dispersive directions of the analyzer. The present electron analyzer is specially designed with a narrow curved entrance slit and a wide exit slit coupled with an exit lens system after the toroidal deflector, which can give a wide energy dispersed range of 20% of the mean pass energy and a large angular range extending from 30° to 120°. The performance of the spectrometer has been studied by measuring the scattered electrons from Ar atoms and from a highly oriented pyrolytic graphite surface, indicating the usefulness of the present analyzer in electron spectroscopy. A brief description of the method for a spectrum transformation from Cartesian coordinates to polar coordinates is also presented. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149696
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  • 7
    Electronic Resource
    Electronic Resource
    Improved design of cusp-type electron-cyclotron resonance ion sources (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3873-3875 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ion source of electron-cyclotron resonance using cusp magnetic field is designed. The field is generated with two cylindrical magnets polarized parallel to the axis of symmetry. Lines of magnetic induction are in this configuration longer than in conventional cusp machines. The plasma electrons escaping from a line cusp are repelled by applying negative potential to an electrode repeller. The repeller of low work function emits additional electrons. A whistler wave is launched through a helical antenna at a point cusp to produce overdense plasmas. An intense ion beam is formed by extracting ions at the other point cusp where the magnetic flux is focused. The repeller materials are sputtered at the line cusp and ionized in the plasma. The atomic flux from the cylindrical surface is focused at the center of plasma to give abundant ions from the solid materials. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145452
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  • 8
    Electronic Resource
    Electronic Resource
    Study of laser-imploded core plasmas with an advanced Kirkpatrick–Baez x-ray microscope : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 824-827 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We developed an advanced Kirkpatrick–Baez (AKB) x-ray microscope which consisted of two hyperbolic mirrors and two elliptic mirrors. The spatial resolution of (approximately-less-than)3 μm was realized over ∼1 mm diam. This AKB microscope was used for x-ray imaging in laser fusion experiments. Laser absorption nonuniformity with a large wave number on a spherical solid target or a plane slab target was estimated by measurements of x-ray emission from the target surface with the microscope. The x-ray images of the imploded core plasmas were also obtained with the AKB microscope, changing the laser focus condition and the laser energy balance. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147699
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  • 9
    Electronic Resource
    Electronic Resource
    Laser-imploded core structure observed by using two-dimensional x-ray imaging with 10-ps temporal resolution : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 722-724 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Core plasmas of laser-imploded ICF targets were observed by using a 10-ps temporally resolved two-dimensional x-ray imaging technique. A multi-imaging x-ray pinhole camera was coupled to an x-ray streak camera, and two-dimensional images were reconstructed by handling the streaked image data. Image distortion of the system was evaluated and nonuniformity in sensitivity was corrected. The spatial resolution was 15 μm and the observed photon energy was 2.2–4.9 keV. Structures in the x-ray image of the core were found to be rapidly changing with 10-ps time scale. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146482
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of linewidths of Ne-like germanium soft x-ray laser in slab targets (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3610-3616 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe our measurements of linewidths of the two J=2-1 transitions (232.24 and 236.25 A(ring)) and the J=0-1 transition (196.20 A(ring)) of Ne-like germanium soft x-ray laser in slab targets. The high resolution spectral measurement was performed using a grazing incidence spectrometer with an x-ray CCD camera. Time integrated linewidths, the full width at half maximum, of the two J=2-1 lasing lines are about 20(±4) mA(ring) when the gain-length product (GL) is ∼8. The linewidth of the J=0-1 line is measured to be 25 mA(ring) as the GL is ∼5. The measured linewidths of the 236.25 A(ring) line are slightly narrower than those of 232.24 A(ring) in the same shot, reflecting their different intrinsic linewidths. For the J=2-1 transitions, the thermal Doppler broadening (43 mA(ring) inhomogeneous) has been obtained by one-dimensional hydrodynamic simulation of the plasma expansion, and the collisional broadening (15 mA(ring) homogeneous) has been considered with all inelastic electron collisional rates among the transition levels in the plasma. The predicted 52 mA(ring) Voigt profile intrinsic linewidth for the 236.25 A(ring) line has been used to calculate linewidth narrowing by the one-dimensional model of amplified spontaneous emission. The experimental data are in agreement with the model calculation in the short targets. Spectral narrowing is not evident in the long targets. We examined soft x-ray propagation in the plasma by ray-trace calculation. It is shown that refraction is an important factor affecting the spectral narrowing of soft x-ray lasers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359937
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