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  • 1
    Electronic Resource
    Electronic Resource
    Investigations of the 147 nm radiative efficiency of Xe surface wave discharges (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1087-1092 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The radiative efficiency of the 147 nm resonance radiation of Xe excited in a low pressure, high-frequency surface wave sustained plasma has been investigated. The radiative UV power has been obtained from optical absorption spectroscopic measurements of the Xe resonance level population and from Monte Carlo calculations of the effective decay rate of this level. Precise measurements of the rf power absorbed by the plasma enable the determination of the absolute vacuum ultraviolet discharge efficiency for the Xe surface wave discharge. Results show efficiencies up to more than 80(±11)% . © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363851
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  • 2
    Electronic Resource
    Electronic Resource
    A radiometric and electrical characterization of low pressure dc positive column sulfur discharges (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 86-92 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dc positive column sulfur (S) and S–Ar discharges have been studied over a wide range of operating conditions. Even though the equilibrium partial pressure of S2 is low in the 50 °C–200 °C temperature range investigated here, the primary radiating molecule in these discharges is S2. Electronic collisions dissociate S8 to produce the radiating S2 molecules at densities far in excess of the equilibrium density. The majority of the spectral emission occurs in the 2800–3500 A(ring) range. The spectrum observed from these discharges corresponds nicely to that obtained from dc discharges at much higher temperatures. The radiation output has been studied as a function of input power, wall temperature, buffer gas pressure, discharge radius, and cold spot temperature. The absolute efficiency of the discharge in generating near-ultraviolet radiation has been measured and the results are presented for many areas of the multidimensional parameter space. The maximum efficiency of ultraviolet and visible emission obtained was approximately 17%. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360794
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  • 3
    Electronic Resource
    Electronic Resource
    A radiometric investigation of low-pressure rf sulfur discharges (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7523-7528 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This investigation focuses on low-pressure S2 molecular rf discharges for use as diffuse radiators. Cylindrical fused silica S2–Ar and S2–Ne lamps have been tested at 13.56 MHz and the absolute radiative efficiencies have been measured. The radiation is emitted primarily between 2800 and 3500 A(ring). The UV radiative efficiencies were studied as a function of input power, buffer gas pressure, discharge radius, and applied external cooling. The maximum observed efficiency for a low power density, diffuse rf discharge is 7%. The measured UV efficiencies of the 13.56 MHz discharges are somewhat lower than those of low-pressure S2–Ar dc discharges. A reentrant lamp design has been tested as well and no improvements in efficiency were observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362424
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  • 4
    Electronic Resource
    Electronic Resource
    Ultraviolet spectroscopy of gaseous species in a hot filament diamond deposition system when C2H2 and H2 are the input gases (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3142-3150 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The methyl radical density, acetylene mole fraction, filament properties, and diamond growth rate and film quality are measured in a hot filament chemical vapor deposition system when C2H2 and H2 are used as the input gases. The methyl radical density and acetylene mole fraction depend greatly on the degree of filament surface poisoning. This poisoning prevents diamond growth due to a lack of hydrogen atoms and/or methyl radicals. Understanding the large influence of the filament surface catalytic characteristics is important for developing a gas phase model of this system. The results obtained with C2H2 and H2 as the input gases are compared to those obtained with CH4 and H2 as the input gases. Under conditions when the filament surface is not poisoned, the methyl radical concentrations are similar when either C2H2 and H2 are the input gases or when CH4 and H2 are the input gases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356169
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement of C6H6 densities in a diamond deposition system (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 4647-4650 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the absolute column densities of gas phase C6H6 and upper limits on absolute C4H2 and C2H3 concentrations in a hot filament diamond chemical vapor deposition (CVD) reactor. The steady state density of C6H6 is monitored as a function of C2H2 and H2 input fractions. The C6H6 column density is a quadratic function of input C2H2 fraction at low C2H2 fractions. Above a critical C2H2 input fraction, the C6H6 column density becomes independent of C2H2 input fraction. The column density of gas phase C6H6 is relatively insensitive to the input H2 fraction. The weak relationship between C6H6 and H2 input fraction is in contradiction to the conclusion drawn from chemical kinetics modeling of diamond CVD that H2 strongly suppresses the formation of aromatic species under diamond CVD conditions. Moreover, comparison of C6H6 column densities with previously measured CH3 column densities under similar conditions indicate that a comparable fraction of gas phase carbon atoms in the steady state are incorporated in C6H6 as are incorporated in the growth species CH3. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478347
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  • 6
    Electronic Resource
    Electronic Resource
    Atomic and radical densities in a hot filament diamond deposition system (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9111-9119 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The gas phase densities of atomic carbon, atomic hydrogen, and methyl radicals are measured in a hot filament diamond deposition system by the use of absorption spectroscopy in the vacuum ultraviolet. The ratio of atomic to molecular hydrogen is also determined using the measured C and CH3 densities and the equilibrium constant for the hydrogen abstraction and recombination reactions that link the C and CH3 densities. The flux of C to the diamond surface is inadequate to explain the total growth rate, though C could have an important role in initiating growth. A model indicates that the hydrogen is dissociated at the filament and diffuses quickly throughout the rest of the system; gas phase reactions only have a small effect on the degree of dissociation. An increased input CH4 mole fraction results in lower hydrogen dissociation by poisoning the catalytic properties of the filament. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471443
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  • 7
    Electronic Resource
    Electronic Resource
    High sensitivity absorption spectroscopy in glow discharge plasmas (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 45-48 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A highly sensitive absorption experiment for diagnosing glow discharge plasmas is described. This experiment is applicable from the VUV to the IR. A very stable Xe arc lamp is used as a source of continuum radiation. An echelle spectrometer equipped with a gated, image-intensified, charge-coupled device detector array is used to disperse and detect the continuum, with absorption features, after it has traversed the glow discharge. Digital subtraction is used to discriminate against the line emission from the glow discharge and detect only the continuum emission from the arc discharge. Estimates of the relative spectral radiances of glow and arc discharges suggests the subtraction technique is broadly applicable to glow discharge studies. A fractional absorption of 10−3 is detectable with a signal-to-noise ratio limited primarily by shot noise. A detection limit for excited Hg atoms of 7×109 cm−2 is demonstrated in a 400-mA Hg–Ar glow discharge. Further improvements in the experiment are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144399
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of the Hg distribution in a high-pressure arc lamp by x-ray absorption (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 3066-3072 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used an x-ray absorption technique to measure the distribution of Hg atoms in a pure-Hg high-pressure arc lamp. The x rays are obtained from a molybdenum-anode x-ray tube at an accelerating potential of 25.3 kV. The spectral distribution of x rays which produce the absorption signal consists mainly of the Mo Kα and Kβ fluorescence peaks at 17.5 and 19.6 keV, respectively. Plane-wave illumination of the lamp and two-dimensional detection of the transmitted x rays allow us to probe the Hg atom density in all regions of the lamp, simultaneously, with a spatial resolution of 170 μm. A complete two-dimensional map of the density is obtained by Abel inversion of the absorption data. This map extends all the way out to the arc-envelope boundary and includes the cold regions of the discharge behind the electrodes. A temperature map of the discharge is obtained by combining the density information with an optical emission measurement of the core temperature at a single axial location. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368461
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  • 9
    Electronic Resource
    Electronic Resource
    Resonance radiation transport in inhomogeneous media: Cylindrical glow discharges (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 731-737 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical simulations of radiation transport in cylindrical geometry are used to determine the effect of radially symmetric inhomogeneities. The focus of this study are inhomogeneities such as may be produced by radial cataphoresis or temperature gradients in cylindrical glow discharges, i.e., a quadratic profile of absorbing atoms which has a minimum on the axis of the cylinder. A propogator function analysis of the Holstein–Biberman equation and a Monte Carlo simulation of resonance photon scattering are simultaneously used to examine three limiting cases of interest: (i) a pure Doppler broadened atomic lineshape, (ii) a pure Lorentz atomic lineshape produced by foreign gas broadening, and (iii) a pure Lorentz atomic lineshape produced by resonance collision broadening. The fundamental mode distribution of excited atoms, the fundamental mode trapped decay rate, and the volume-averaged escape rate for a homogeneous production rate per unit volume are calculated for each of these cases. The trapped decay rates are found to change modestly (depending upon lineshape) as the degree of inhomogeneity is increased, if the volume integral of the absorbing atom density remains fixed. Correction factors for the fundamental mode trapped decay rate are reported. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370796
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  • 10
    Electronic Resource
    Electronic Resource
    A framework for modeling the cathode fall illustrated with a single beam model (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1775-1780 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A framework for a model of the cathode fall region of a dc glow discharge is presented, and a simple model is solved as an illustration. An extremum condition independent of the model is placed on the electric field behavior to produce a unique solution that agrees with experiment. The zeroth and second moments of the Boltzmann equation are solved for the electrons with a self-consistent electric field. A single-beam model with only two parameters (number density and beam velocity) is assumed for the electron distribution function. Ion motion is modeled with a parametric fit to known ion mobilities. The model is solved for conditions corresponding to the experimental results and to Monte Carlo simulations of Doughty, Den Hartog, and Lawler [Phys. Rev. Lett. 58, 2668 (1987)]. The results are in good qualitative and "factor-of-two'' quantitative agreement with the published results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341774
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