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  • 1990-1994  (11)
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  • 1
    Electronic Resource
    Electronic Resource
    Aluminum-coated optical fibers as efficient infrared timing fiducial photocathodes for synchronizing x-ray streak cameras (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6935-6944 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The timing fiducial system at the Nova Two-Beam Facility allows time-resolved x-ray and optical streak camera data from laser-produced plasmas to be synchronized to within 30 ps. In this system, an Al-coated optical fiber is inserted into an aperture in the cathode plate of each streak camera. The coating acts as a photocathode for a low-energy pulse of 1ω (λ = 1.054 μm) light which is synchronized to the main Nova beam. The use of the fundamental (1ω) for this fiducial pulse has been found to offer significant advantages over the use of the 2ω second harmonic (λ = 0.53 μm). These advantages include brighter signals, greater reliability, and a higher relative damage threshold, allowing routine use without fiber replacement. The operation of the system is described, and experimental data and interpretations are discussed which suggest that the electron production in the Al film is due to thermionic emission. The results of detailed numerical simulations of the relevant thermal processes, undertaken to model the response of the coated fiber to 1ω laser pulses, are also presented, which give qualitative agreement with experimental data. Quantitative discrepancies between the modeling results and the experimental data are discussed, and suggestions for further research are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347631
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Imaging of laser-irradiated targets at a wavelength of 33.8 A(ring) using a normal-incidence multilayer mirror (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1997-2002 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The morphology of the 33.8 A(ring) emission from laser-irradiated targets was studied using a concave mirror with a W/B4C multilayer coating. The mirror had peak normal-incidence reflectance of 1.8% at a wavelength of 33.8 A(ring). The emissions from a variety of targets were imaged on film with a spatial resolution of 30 μm in the target plane. Radiatively heated, low-density plastic and silica foams, x-ray laser targets, and a gas-filled enclosure were imaged. Several targets were simultaneously imaged at wavelengths of 33.8 and 130 A(ring) using two normal-incidence microscopes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870655
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Tabletop x-ray lasersf| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1744-1752 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Details of schemes for two tabletop size x-ray lasers that require a high-intensity short-pulse driving laser are discussed. The first is based on rapid recombination following optical-field ionization. Analytical and numerical calculations of the output properties are presented. Propagation in the confocal geometry is discussed and a solution for x-ray lasing in Li-like N at 247 A(ring) is described. Since the calculated gain coefficient depends strongly on the electron temperature, the methods of calculating electron heating following field ionization are discussed. Recent experiments aimed at demonstrating lasing in H-like Li at 135 A(ring) are discussed along with modeling results. The second x-ray laser scheme is based on the population inversion obtained during inner-shell photoionization by hard x rays. This approach has significantly higher-energy requirements, but lasing occurs at very short wavelengths (λ≤15 A(ring)). Experiments that are possible with existing lasers are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870936
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A simple method for overcoming spatial resolution limitations in soft x-ray spectrograph/detector systems : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5122-5123 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a simple method for improving the spectral resolution of soft x-ray and extreme ultraviolet spectrographs which use electro-optical detector/intensifiers. In this method, the spectrometer is focused onto a narrow slit which is angled near 90° with respect to the dispersive axis and placed just in front of the detector. Proper choice of the width and angle of the slit is shown to have the effect of expanding the spectrum along the length of the slit to the point where the spatial resolution limitations of the detector are overcome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143459
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Studies of K- and L-shell x-ray emission from laser plasmas for use as a high-energy backlighter (abstract) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2816-2816 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We are developing a backlighter in the 4–10 keV energy range using K-shell spectra from elements with Z≤30 and the L-shell spectra from elements with Z≥58. Using one beam of the Nova laser yielded about 3.0 kJ of 0.53 μm wavelengths light in a 1.0 ns square pulse which was focused to a spot of less than 100 μm in diameter on 12.5 and 25.0-μm-thick foil targets. Our initial results include time-resolved spectra from slab (2 mm×2 mm) and disk (100 μm diameter) targets of Ce (Z=58), Zn (Z=30), and Ti (Z=22). The Zn and Ti exhibit strong emission from the cold Kα line and satellite states, while the Ce spectra show prominent L-band structure. By exploring the differences between disks matched to the beam focus and extended slabs we hope to obtain information on plasma cooling mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141795
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Short wavelength x-ray laser research at the Lawrence Livermore National Laboratory (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2326-2337 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laboratory x-ray lasers are currently being studied by researchers worldwide. This paper reviews some of the recent work carried out at Lawrence Livermore National Laboratory. Laser action has been demonstrated at wavelengths as short as 35.6 A(ring) while saturation of the small signal gain has been observed with longer wavelength schemes. Some of the most successful schemes to date have been collisionally pumped x-ray lasers that use the thermal electron distribution within a laser-produced plasma to excite electrons from closed shells in neon- and nickel-like ions to metastable levels in the next shell. Attempts to quantify and improve the longitudinal and transverse coherence of collisionally pumped x-ray lasers are motivated by the desire to produce sources for specific applications. Toward this goal there is a large effort underway to enhance the power output of the Ni-like Ta x-ray laser at 44.83 A(ring) as a source for x-ray imaging of live cells. Improving the efficiency of x-ray lasers in order to produce saturated output with smaller pump lasers is also a goal of this work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860203
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    High-resolution absorption and emission spectroscopy of high Z laser-produced plasmas (abstract) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2814-2814 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Up to 7 kJ of 0.53 μm laser light was used to irradiate solid and thin foil high Z disk targets. The 1 ns flat-topped laser pulses were focused to an intensity greater than 1016 W/cm2. The spectra were recorded on a 3 m grazing incidence spectrograph. We have extended the range of ions observed to emit lines in the O-like, F-like, Na-like, and Cu-like isoelectronic sequences. In addition, layered targets and atomic mixtures have been used to study opacity effects and VUV line emission. This work was performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141791
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    X-ray lasers as sources for resonance-fluorescence experiments (1994)
    Springer
    Applied physics 58 (1994), S. 7-11 
    Details
    ISSN: 1432-0649
    Keywords: 42.55.Vc ; 32.30.Rj ; 52.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We point out that existing Ne-like X-ray lasers have sufficient brightness to be used as pump sources in resonant pump-fluorescence experiments, and we discuss some of the potential benefits and limitations of such experiments. In preliminary experiments, we have measured the line overlap of the Ne-like yttrium X-ray laser near 155 Å with 4f−3d transitions in H-like Na and He-like Mg. These experiments used a high-resolution grating spectrometer, and calibrated the wavelength of the yttrium laser by comparison against lines of known wavelength. The results indicate that the wavelength of the yttrium laser is 154.985 ± 0.025 Å, a factor of 2–4 improvement in precision over previous calibrations. We find that the yttrium laser is ≈ 100 mÅ to the long-wavelength side of both the He-like Mg line and the H-like Na line, so that neither resonance is perfect; however, Stark broadening could improve the overlap in the latter scheme, and bulk Doppler shifting could improve both resonances. We also find a good resonance between the yttrium laser and an un-identified transition which we tentatively attribute to copper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081706
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Collisional excitation X-ray laser experiments in plasmas produced by 0.53-μm and 0.35-μm laser light (1990)
    Springer
    Applied physics 50 (1990), S. 257-264 
    Details
    ISSN: 1432-0649
    Keywords: 42.55.Hq ; 52.50.Jm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent Ne- and Ni-like X-ray laser experiments carried out at the Centre d'Etudes de Limeil-Valenton (CEL-V) are reviewed. A variety of experiments in Ne-like X-ray lasers were performed; here we discuss measurements of soft X-ray amplification in Ge (Z=32) and Sr (Z=38) plasmas. In Ge plasmas produced by 0.53-μm laser light at an irradiance of 6.0×1013 W/cm2, gains between 2.2–2.5 cm−1 on the 232.2 and 236.2 Å J=2−1 lines and a gain of 1.0 cm−1 on the 196.1 Å J=0−1 line were measured. In addition, gains of 4.4 cm−1 and 4.0 cm−1 have been demonstrated on the J=2−1 transitions at 164.1 and 166.5 Å in Nelike Sr at laser intensities of 1.3×1014 W/cm2. The effects of pumping the Ne-like Se X-ray laser with 0.35-μm laser light have also been investigated; the Se lasing spectra is similar to that obtained with 0.53-μm light. Experiments have also been carried out to optimize the gain of the 50.3 Å Ni-like Yb (Z=70) J=0−1 line. For Yb, no significant increase in gain over that previously reported was seen, but the time history of the Ni-like Yb X-ray laser was measured for the first time. Finally, attempts to extrapolate the Ni-like results to shorter wavelength were made using Ta (Z=73), W (Z=74), and Re (Z=75). No definitive observation of the Ni-like J=0−1 lasing lines was made in these experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325057
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    First observation of lasing at 231 Å in neon-like nickel using the prepulse technique (1993)
    Springer
    Applied physics 57 (1993), S. 309-311 
    Details
    ISSN: 1432-0649
    Keywords: 42.60.By ; 32.30.Rj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report lasing for the first time in nickel on the neon-like J=0→1, 3p→3s transition at 231 Å as well as several weaker transitions including the J=2»1 lines at 298 Å and 304 Å. Amplification is seen only when the prepulse technique of using a low intensity prepulse before the main optical drive pulse is used to illuminate the nickel target. The prepulse technique is also shown to produce lasing in copper and dramatically improve the output of the germanium laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332454
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    Paper (German National Licenses)
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