Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Temperature and concentration profiles in a low pressure methane process plasma (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1297-1302 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coherent anti-Stokes Raman scattering (CARS) is applied to a microwave (2.45 GHz) excited plasma used for plasma enhanced chemical vapor deposition. The applicability of CARS to low pressure (2 Pa) plasmas is verified, and the absence of saturation is carefully checked. Ground state concentration profiles as well as rotational temperatures of CH4 are presented with high spatial and temporal resolution. The measurements show a decrease of the CH4 ground state density under the influence of the plasma down to ≈25% (nCH4=1.0×1020 m−3) of its initial value. The rotational temperature is nearby room temperature across the total discharge volume. A straightforward modeling of the plasma explains the decrease of CH4 ground state densities as an effect of electron collisions and delivers an approximate value of the electron temperature of about 3 eV. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360371
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Time-resolved study of a laser-induced surface plasma by means of a beam-deflection technique (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2291-2297 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fast-beam deflection technique is used to investigate the transient behavior of a laser-induced surface plasma generated by CO2-laser pulses of 2-kW average power near an aluminum surface in various protective gas atmospheres, with a typical pulse energy of 3.3×10−2 J, a pulse repetition rate of 60 kHz, and an average peak power per pulse of 30 kW, corresponding to an intensiy of 6×1012 W/m2. As a laterally probing beam, a cw 10-W CO2 laser is used, whose beam is focused into a small volume in front of the surface. The electrons of the laser-induced plasma passing this volume diffract the cw CO2 laser beam, and the resulting beam deflection is determined by means of a partially absorbing CaF2 wedge in connection with a fast infrared detector. The evaluation of beam deflection 0.15 cm above the surface renders a maximum electro density of 2×1023 m−3 for a surrounding argon atmosphere and 0.7×1023 m−3 for pure helium. Additives of O2 reduce the attainable electron density even more. No plasma can be detected below a threshold of, say, 10 mJ energy per laser pulse. It is verified that high electron density as in the case of argon shields the surface against the incoming CO2 laser pulses so that material processing, such as welding, is rather poor. Better welding results are achieved in helium-oxygen mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341657
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ellipsometric measurement of the optical constants of solid and molten aluminum and copper at λ=10.6 μm (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 1326-1332 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The index of refraction, the extinction coefficient, and the absorptance were measured under ultrahigh vacuum conditions in a temperature range from 295 to 1000 K for aluminum and from 295 to 1400 K for copper for the CO2 laser wavelength at λ=10.6 μm. A photometric infrared ellipsometer was applied. The absorptance of the clean metallic surfaces jumps discontinuously from 3% to 7% in the case of aluminum and from 2% to 6% in the case of copper at the melting point. Calculations of the optical constants basing on the model of free electrons taking account of the effective mass and the anomalous skin effect describe the measurements for the solid state very well, but are less accurate for the molten state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344431
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Plasma scrape-off effect in a magnetized hollow-cathode arc discharge (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2298-2304 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simultaneous measure of Thomson and Rayleigh light scattering were performed in order to determine electron density, electron temperature, and neutral density distributions in a hollow-cathode arc. These measurements were performed in argon, nitrogen, helium, and hydrogen at approximately 1 Pa. The hollow-cathode arc has also been studied in nitrogen and argon at high pressures ranging from 1–550 Pa. In this paper we present only high-pressure data for nitrogen, although comparison with some results obtained in argon is provided. A plasma scrape-off effect leads to a reduction in electron density in front of the anode and consequently to an enhancement of the anode fall. This enhancement was detected through an increase in electron temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341658
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Electric probe measurements of the normal cathode fall in CO2 laser discharges (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5251-5253 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An electric probe was used for measurements of the normal cathode fall in a glow discharge in flowing CO2 laser mixtures (CO2:N2:He=4.5:13.5:82 and 5:20:75) for uncooled copper, stainless-steel and tungsten cathodes. The results imply that the cathode fall value in the mixture is governed mainly by the presence of carbon dioxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350584
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Interaction of CO2 laser pulses of microsecond duration with Al2O3 ceramic substrates (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 75-81 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The working efficiency and other properties of laser-induced surface plasmas have been compared for the case where two kinds of CO2 laser pulse interact with alumina substrates. Pulses of several times 10-μs duration are able to drill hole patterns while producing negligible mechanical stresses in the material. However, because of the formation of a laser-induced plasma which shields the material against the incoming laser beam, the drilling efficiency is rather low. A simple vaporization model shows that 30%–100% of the laser-pulse energy is used for material processing. There is in addition a threshold energy of about 50 mJ, below which no material processing occurs. Plasma diagnosis verifies characteristic times of absorptive modulation in the range of 5–10 μs. Therefore, laser pulses of high repetition rate ((approximately-greater-than)10 kHz) and of a pulse duration below 5 μs have been used in order to overcome the above-mentioned disadvantages. An important role with respect to the shielding effect is played by the electron density inside the laser-induced plasmas, because the absorption coefficient of the laser light in these surface plasmas is proportional to the square of the electron density. The spatial and temporal distribution of the electron density during material processing is therefore continuously monitored by a beam-deflection technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350246
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Measurements of the optical constants of solid and molten gold and tin at λ=10.6 μm (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1642-1647 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The index of refraction, the extinction coefficient, and the absorptance for gold and tin were measured in a temperature range from room temperature up to the melting point for the wavelength λ=10.6 μm. All measurements were performed under ultrahigh-vacuum conditions using a photometric infrared ellipsometer with a rotating analyzer. Measurements verify a discontinuous jump of the absorptance at the solid-to-liquid phase transition from 3.5 to 6.5% in the case of gold and from 4.9 to 9.2% in the case of tin. The experimental results derived for the clean solid surface are in good agreement with the theoretical prediction by a Drude model, if additionally appropriate effective masses and the anomalous skin effect are taken into account. This theory is much less accurate if applied to the molten state of gold and tin, as was already shown previously for liquid aluminum and copper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349530
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Potential and velocity measurements in a magnetized hollow cathode discharge by means of electric probes and laser induced fluorescence (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 3044-3052 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By means of electric probes, surfaces of equal electrical potential are measured in the plasma of a magnetized hollow cathode arc burning in argon. At moderate distances between the cathode and the anode the potential increases nearly linearly in proceeding in the axial direction from the cathode to the anode. In the radial direction a potential growth can be observed up to a plateau regime near the plasma edge. If the cathode–anode distance exceeds a critical length, the situation changes insofar as a voltage jump of nearly a factor of 2 occurs near the anode where higher voltage values are reached than on the anode surface. There the voltage drops in the radial direction to the outside plateau value. This voltage distribution is produced by a (positive) anodic space charge cloud, which accelerates the electrons. The voltage jump guarantees the transport of the arc current even in the case of a long arc. This space charge decelerates the ions flying in the axial direction and creates the possibility of ions rotating around the cathode–anode axis in the anode regime. This latter possibility was examined by monitoring the frequency resolved Doppler shift of the argon ion line at λ=611.49 nm measured by laser induced scattering. The flow field of the ions can be quantitatively understood from the spatial distribution of the electrical potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866961
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Measurements of absorption coefficients of water vapor by means of an H"2O laser in the far-infrared
    Amsterdam : Elsevier
    Infrared Physics 19 (1979), S. 585-592 
    Details
    ISSN: 0020-0891
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0020-0891(79)90077-0
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Laser diagnostics of a low-pressure hollow-cathode arc
    Amsterdam : Elsevier
    Journal of Quantitative Spectroscopy and Radiative Transfer 34 (1985), S. 309-320 
    Details
    ISSN: 0022-4073
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-4073(85)90012-3
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...