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  • 1
    Electronic Resource
    Electronic Resource
    Self-focussing of a laser beam in a multiply ionized, absorbing plasma (1979)
    Springer
    Applied physics 18 (1979), S. 199-204 
    Details
    ISSN: 1432-0630
    Keywords: 42.65 Hw ; 52.40 Db ; 52.40 Mj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Using a numerical code we have studied self-focussing of an intense laser beam which is propagating through a multiply-ionized absorbing plasma. The effecient self-focussing threshold has been calculated as a function of various pulse and plasma parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00934416
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  • 2
    Electronic Resource
    Electronic Resource
    Laser ablation of carbon at the threshold of plasma formation (1999)
    Springer
    Applied physics 69 (1999), S. S121 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 52.50.Jm; 79.20.Ds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The ionization of laser-ablated vapours with lasers producing ns duration pulses at various wavelengths has been studied in order to understand the mechanisms of the vapour–plasma transition. It has been established that there are several regimes characterizing the laser–target interaction which depend on laser intensity, wavelength, and pulse duration. The range of laser intensities for optimal laser evaporation is determined by the condition of transparent vapours. The intensity range is upper-limited by the opaque plasma formation due to vapour optical breakdown. Results are given for laser evaporation of graphite with Nd:YAG laser (1.064 μm), KrF laser (248 nm) and ArF laser (193 nm). For the UV laser wavelength the regime of skin-effect interaction was proposed as the mechanism of ion acceleration, and the range of validity of the skin-effect mode was established. With UV lasers the interaction has a bimodal nature: the interaction may proceed initially in the skin effect regime, resulting in a few high-energy ions, until hydrodynamic expansion begins at a later stage. The skin-effect interaction at the initial stage of the UV laser pulse gives the first, to our knowledge, explanation for the acceleration of ions up to ∼100 eV at low laser intensities of 108–109 W/cm2 and ns-range pulse duration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003399900387
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  • 3
    Electronic Resource
    Electronic Resource
    Suppression of fast-ions from a laser-produced plasma
    Amsterdam : Elsevier
    Physics Letters A 58 (1976), S. 399-401 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(76)90677-0
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence of magnetic fields imprinted in ferromagnetic targets by the spontaneous magnetic field of a laser-produced plasma demonstrated by after-pulse pulsations of Kα emission (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3676-3683 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The observation of an unusually long sequence of Kα pulses from planar Fe foil targets irradiated by a 180 ps laser pulse at intensities of(0.1–3)×1016 W/cm2 is presented. The duration of the Kα emission was up to 5 ns: approximately 30 times longer than the laser pulse. A proposed interpretation of these observations is that suprathermal electrons generated in the laser-produced plasma survive after the laser pulse and are gradually decelerated as they circulate in the magnetic field imprinted during the laser pulse in the ferromagnetic target material. Short bursts of Kαemission occur as these electrons pass through the target. The magnetic field in the cold part of the ferromagnetic target with temperature below the Curie temperature is an integral imprint of the spontaneous magnetic field generated in the laser-produced plasma. A model of this process provides a good fit to the experimental data. The effect could be useful as a diagnostic tool for measuring the spontaneous magnetic field and the energy of fast electrons. These results also open an opportunity for studies of magnetization processes in a ferromagnetic at an extremely high magnetic field: on the megagauss scale. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872565
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  • 5
    Electronic Resource
    Electronic Resource
    Ablation of solids by femtosecond lasers: Ablation mechanism and ablation thresholds for metals and dielectrics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 949-957 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. It is shown that at high intensities when the ionization of the target material is complete before the end of the pulse, the ablation mechanism is the same for both metals and dielectrics. The physics of this new ablation regime involves ion acceleration in the electrostatic field caused by charge separation created by energetic electrons escaping from the target. The formulas for ablation thresholds and ablation rates for metals and dielectrics, combining the laser and target parameters, are derived and compared to experimental data. The calculated dependence of the ablation thresholds on the pulse duration is in agreement with the experimental data in a femtosecond range, and it is linked to the dependence for nanosecond pulses. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1447555
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  • 6
    Electronic Resource
    Electronic Resource
    An experimental study of magnetic fields in plasmas created by high intensity one micron laser radiation (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2286-2297 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic fields generated in plasmas formed by focusing intense picosecond (∼20 psec) duration Nd: laser pulses onto disk targets have been studied using simultaneous polarimetry and interferometry for a wide range of laser and plasma parameters. Megagauss fields, which extend throughout the plasma corona, have been observed during the pulse, but subsequently these decay rapidly and are unobservable only 100 psec after the pulse peak. The general morphology of the field together with this rapid decay suggests a role for the superthermal particles in magnetic field generation and saturation (via convection). Hard x-ray (∼20 keV) imaging has been used to relate the regions of energy deposition by superthermal electrons to the magnetic field structure. The results are compared with the predictions of recent two-dimensional (2-D) computer simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865282
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrafast ablation with high-pulse-rate lasers. Part II: Experiments on laser deposition of amorphous carbon films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4222-4230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrafast pulsed laser deposition is a novel technique for depositing particle-free, thin solid films using very high repetition rate lasers. The process involves evaporation of the target by low energy laser pulses focused to an optimum intensity to eliminate particles from the vapor. This results in films with very high surface quality while the very high repetition rate increases the overall deposition rate. Here we report an experimental demonstration of the process by creating ultrasmooth, thin, amorphous carbon films using high repetition rate Nd:YAG lasers. Both a 10 kHz, 120 ns Q-switched Nd:YAG laser, or a 76 MHz 60 ps mode-locked Nd:YAG laser were used in the experiments. The number of particles visible with an optical microscope on the carbon film deposited using the mode-locked laser was less than one particle per mm2. Scanning electron microscopy images demonstrated that the deposited film had a very fine surface texture with nanoscale irregularities. Atomic force microscopy surface microroughness measurements revealed a saturation-like behavior of the root-mean-square roughness at 〈12 nm over the whole deposited surface area for 10 kHz Q-switched laser evaporation; and almost at the atomic level (〈1 nm) for the 76 MHz mode-locked laser evaporation. Raman spectroscopy of the deposited films indicated that they consisted of a mixture of sp3 and sp2 bonded amorphous carbon. The thickness of the amorphous carbon film deposited simultaneously on two 4 in. silicon wafers varied by only ±5% over an area of ∼250 cm2. The deposition rate was ∼2–6 Å/s at a distance of ∼150 mm from the target, which is 10 to 25 times higher than that achieved with conventional high energy low repetition rate nanosecond lasers. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370334
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  • 8
    Electronic Resource
    Electronic Resource
    Penumbral neutron imaging—optimization and simulation (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1289-1294 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper describes the optimization of the penumbral neutron imaging camera. The optimum parameters are qualified by practical considerations and the resulting camera is tested using a full Monte Carlo simulation. It is shown that an object emitting only 1.3×1010 neutrons/resolution element should be imageable. This result is confirmed by simulations of three different object shapes which indicate that the shape of the core of a compressed inertial confinement fusion pellet may be determined by this technique. It is further shown that these results correspond to the lowest possible imageable yield for any coded-aperture technique using the parameters assumed here. Finally, an alternative aperture and detector arrangement is briefly described which may lower the imageable yield by more than an order of magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337298
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  • 9
    Electronic Resource
    Electronic Resource
    Application of penumbral imaging to thermonuclear neutrons (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 2508-2515 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper describes a study investigating the possible application of penumbral imaging to thermonuclear neutrons generated in experiments on inertial confinement fusion. It is shown that the approach will allow neutron yields as low as 1011 to be imaged with better than 10-μm resolution over a 50-μm field of view. This performance is such that penumbral imaging of neutrons may provide an important diagnostic in near term fusion experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335928
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  • 10
    Electronic Resource
    Electronic Resource
    Subpicosecond laser ablation of dental enamel (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2153-2158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser ablation of dental enamel with subpicosecond laser pulses has been studied over the intensity range of (0.1–1.4)×1014 W/cm2 using 95 and 150 fs pulses at a pulse repetition rate of 1 kHz. The experimentally determined ablation threshold of 2.2±0.1 J/cm2 was in good agreement with theoretical predictions based on an electrostatic ablation model. The ablation rate increased linearly with the laser fluence for up to 15 times the ablation threshold. The absence of collateral damage was observed using optical and scanning electron microscopy. Pulpal temperature measurements showed an increase of about 10 °C during the 200 s course of ablation. However, air cooling at a rate of 5 l/min resulted in the intrapulpal temperature being maintained below the pulpal damage threshhold of 5.5 °C. The material removal rates for subpicosecond precision laser ablation of dental enamel are compared with other techniques. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495896
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