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  • 1
    Electronic Resource
    Electronic Resource
    Spectral measurements from laser-produced plasma in OMEGA (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2171-2173 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Curved- and flat-diffraction crystal spectrographs were developed to collect x-ray spectra from high-atomic-number elements (cadmium–rare earths) in the 5–17-A(ring) region. The plasma source was generated by the 24-beam, frequency-tripled light of the OMEGA laser system. The spectral patterns were identified with the aid of atomic structure calculations and from Moseley plots of isoelectronic sequences. The Ne-like (third-order diffraction) and Na-like ionization stages were observed in the Cd and Sn spectra. The rare-earth spectra were predominantly 3d-4p, 4f transitions over a range of ionization stages involving the M shell. Calibration spectra were obtained with L-series transitions from Fe and Cu targets and K lines from Si plasma excited in the glass supporting stalk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138720
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  • 2
    Electronic Resource
    Electronic Resource
    XUV spectral observations with two-wavelength laser irradiation (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1837-1839 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: XUV diagnostic equipment was designed and utilized on the OMEGA target chamber at the University of Rochester to study high atomic number plasma generation by two-wavelength laser excitation. Spectral data were collected from silver tracer dot targets irradiated with 1/3 TW of 0.35-μm laser light of the multiple-beam OMEGA laser and the single synchronized 1.06-μm beam of the GDL laser for generating energetic electrons. XUV spectral data in the 30–300-A(ring) region were obtained with both a 3-m grazing incidence spectrograph and a compact 1-m grazing incidence spectrograph designed for reentrant mounting in the OMEGA chamber. High-resolution x-ray spectra were acquired in the 3.6–4.2-A(ring) region with a dual, flat-diffraction crystal spectrograph. A low-resolution x-ray spectrum of silver was recorded with a curved mica spectrograph. Some x-ray spectral lines appeared only when both OMEGA and GDL beams were used. These were identified as 2p–3s,3d transitions in F-like Ag xxxix. F-, Na-, and Mg-like lines were found in the grazing incidence spectra, with F-like lines appearing only with 1.06-μm irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140076
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  • 3
    Electronic Resource
    Electronic Resource
    K-shell x-ray yield scaling for aluminum x-pinch plasmas (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 8134-8138 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report results from experiments performed to measure and characterize the intense K-shell radiation from aluminum x-pinch plasmas at peak driving currents ranging from 280 kA to 1.0 MA. Single pulse aluminum K-shell (predominantly line radiation at 1.6–2 keV) x-ray yields ranged from 7.6 J at 290 kA to 240 J at 1.0 MA. In the range from 280 to 470 kA, the yield scales with current to the power of 3.6, whereas nonoptimized K-shell yields at 800 kA and 1.0 MA indicate a power of about 3 or higher.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353452
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  • 4
    Electronic Resource
    Electronic Resource
    Vacuum ultraviolet spectroscopy study of excimer-laser-generated plasmas (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 53-61 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dispersed emission in the vacuum ultraviolet (VUV) (1200–3000 A(ring)) from the plasma generated by the interaction of a KrF excimer laser with an Al and a YBa2Cu3O7 target has been measured. Emission spectra were collected as a function of distance above the target surface and as a function of laser fluence. The qualitative features of the plasmas from the two different targets were similar. The character of the emission spectra changed from a pseudocontinuous emission at the target surface to discrete emission from singly, doubly ionized species as well as neutrals at distances greater than ∼1.5 mm. The spatial variation indicated two regions: a high-density sheath along the target where the core emission is close to blackbody; and beyond, a plasma with large opacity emitting a UV spectrum of intensity decreasing fast with distance. Estimates of the plasma temperature and density were between 2 and 4 eV and ∼1018/cm3, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355267
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  • 5
    Electronic Resource
    Electronic Resource
    Quantitative x-ray emission from a DPF device : 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. 5052-5055 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The x-ray emission was measured from a Dense Plasma Focus (DPF) device. The high density plasma is generated by an electrical discharge in rarefied-neon gas between electrodes in a Mather-type plasma focus configuration. A curved-crystal x-ray spectrograph, a pinhole camera, and an active-filtered photodiode were the diagnostics viewing the axial output of the pinched-plasma region. The x-ray pinhole images indicate a pinched volume roughly 8 mm in length with a nearly circular cross section of about 300 μm in diameter. The digitized spectral traces were computer processed to obtain absolute x-ray line intensities. The neon plasma yielded 10–15 J of K-shell radiation into 4π with the hydrogenlike and heliumlike alpha lines totaling 55%–65% of the total spectral emission. The x-ray emission of the DPF device was studied as a function of discharge current and anode diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143489
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  • 6
    Electronic Resource
    Electronic Resource
    Techniques for soft x-ray absorption in laser-produced plasmas : Eighth topical conference on high—temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2741-2744 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Interest in x-ray absorption derives from soft x-ray transport studies to characterize laser-solid-interaction effects. The object of this work was to determine whether x-ray absorption features were measurable in laser-produced plasmas from solid targets. X-ray emission was made using high-atomic-number microsphere targets irradiated with a focused beam of the Pharos laser while the laser-solid-interaction plasmas were generated by a second beam in Al foil targets. High-resolution, spatially resolved x-ray spectra were collected with instrumentation and geometry similar to previous tracer-dot spectroscopy measurements of plasma profile parameters. Soft x-ray absorption lines, observed at different distances from the aluminum target surface, may be related to density gradients in the laser-generated plasmas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141817
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  • 7
    Electronic Resource
    Electronic Resource
    X-ray damage in optical coatings : 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. 795-797 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Thin film coatings are susceptible to high intensity x-ray damage. The PHAROS III laser was utilized to generate a point source of x-ray emission used to determine the damage threshold of AR-coated space optics. Thin filters coupled with magnets were used to shield the specimens from thermal radiation and plasma debris. Grids supporting the thin filters could be patterned into the coatings. The surface morphology of damaged specimens has been examined with SEM and AFM microscopes to determine the nature of the damage in multilayer AR coatings. Microscopic techniques were used to measure the depths of coating damage and edge sharpness in the patterned region. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146224
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  • 8
    Electronic Resource
    Electronic Resource
    Time-resolved measurements of x-ray damage to optical coatings (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1184-1191 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin film optical coatings are susceptible to damage by high intensity x rays. Time-resolved measurements of this damage are required to better understand the mechanism, so that more rugged coatings can be developed. In the present experiment, dark-field shadowgraphy was used to temporally map the x-ray damage across the surface of certain anti-reflecting (AR) coatings. Two beams from the NRL PHAROS III high power Nd:glass laser system were utilized to generate a point source of plasma x rays, which in turn was used to irradiate and damage the optical coatings. Thin, opaque filters, coupled with permanent magnets and pinholes, were used to shield the optical samples from ultraviolet and charged-particle damage, respectively. The absolute, time-integrated x-ray fluence was measured with a crystal spectrograph, and also was temporally resolved with an x-ray diode. The surface morphology of the damaged optical samples was examined after each shot visually, and later with a profilometer as well as with both scanning electron- and atomic-force microscopes. A measured threshold fluence for damage of 0.049±30% cal/cm2 agrees very well with a radiation-damage code prediction of 0.046 cal/cm2. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363861
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  • 9
    Electronic Resource
    Electronic Resource
    Enhancement of the vacuum ultraviolet emission from excimer laser-generated plasmas by ambient gas atoms (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2490-2492 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the axial (z) and radial (x) distribution of the vacuum ultraviolet emission from excimer laser generated aluminum plasmas in vacuum and in 300 mTorr of argon. The ratio of the radiated line intensities (emission in a gas versus vacuum) on the z axis (i.e., x=0) increased exponentially with distance from the target surface for plasmas generated in a 300 mTorr argon ambient. The absolute line intensities increased linearly with the argon pressure and approximately linearly with the ambient gas atomic cross section when other rare gases were substituted. The line intensity radial distribution was broader for plasmas in argon than in vacuum and the magnitude of the effect increased monotonically with z. The spectral data obtained from plasmas in a gas ambient are discussed in terms of the diffusion of plasma electrons in an ionized gas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110458
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of specimen size and stress rate for the Brazilian test—A statistical analysis (1990)
    Springer
    Rock mechanics and rock engineering 23 (1990), S. 123-134 
    Details
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Summary The Brazilian test is a widely accepted method for the determination of the tensile strength of intact rock. Specifications for the Brazilian tensile strength test have been established by the American Society for Testing and Materials (ASTM), ASTM D 3967-86 and a suggested approach is provided by the International Society for Rock Mechanics (ISRM). The ASTM and ISRM allow a relatively wide range of values for specimen geometry defined in terms of length to diameter ratio and loading rates defined as either time to failure or stress rate. A statistical study was carried out on a coal measure sandstone to determine whether the tensile strength determined by the Brazilian test is independent of the specimen geometry and the stress rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01020397
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