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  • 1
    Electronic Resource
    Electronic Resource
    Spatial characteristics of electron swarm parameters in gases (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 4024-4029 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of a Monte Carlo simulation study focusing on the spatial characteristics of swarm parameters in an isolated electron swarm and the distribution of the electron density and flux taking into account the anode boundary are presented. The spatial variation of the swarm parameters is interpreted using conventional swarm theory, and potential problems with the measurement of arrival-time spectra of electrons are considered. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367157
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electron swarm parameters in ramp electric fields (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2902-2908 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The behavior of electron swarms in gases in time-varying ramp electric fields is investigated using a Monte Carlo simulation. In particular, we consider the case of swarms in chlorine gas. Swarm parameters as a function of instantaneous E/N(E is the electric field and N is the gas number density) for different dE/dt are determined. At higher dE/dt, all the parameters as a function of E/N are shifted to larger E/N when compared to the steady-state case. The drift velocity curve develops a peak which shifts to higher E/N and increases in magnitude as dE/dt is increased. Next, we pay attention to the definition of the swarm parameters, where the parameters derived from kinetic theory and by analogy to experiment are compared. For the high dE/dt cases, differences in the swarm parameters at the same E/N values are caused by the inertia of the electrons and their transient beam-like high drift velocity, while discrepancies due to the difference between the definitions in the kinetic theory and in the analogy to experiment appear significantly. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361286
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Simulations of step responses of electronegative radio-frequency capacitively coupled discharges (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1848-1858 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transient response of electronegative radio-frequency glow discharges is important for process control, charge free etching, and highly selective etch applications. The step response of typical electronegative process gases (silane at 1 Torr and chlorine at 100 mTorr) is studied using a drift-diffusion model for silane and a three-moment model for chlorine. The silane simulations include a blocking capacitor whereas the chlorine results do not. For the silane results with a blocking capacitor in series with the plasma, it is found that there are three types of transients. Depending on the final steady-state value of the source rf voltage, the step response can be characterized either by smooth transitions in the number densities of species in the discharge from one steady state to the next, temporary extinction of the discharge or a discharge mode characterized by temporary extinction and reignition of the discharge. In the case of silane definite thresholds separate the phenomena. The step response of the chlorine discharges is always characterized by a smooth transition from one steady state to the next. Smooth transitions from one steady state to the next in the case of step decreases in the source voltage are possible since decrease of the negative ion density in the bulk is controlled by ion–ion recombination. It appears that the temporary extinction of the discharge and natural pulsed steady state is the consequence of how the voltage is divided between the gap and the blocking capacitor during the transient and the fact that the attachment coefficient becomes larger than the ionization coefficient at low values of reduced electric field. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368343
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  • 4
    Electronic Resource
    Electronic Resource
    A two-dimensional model of laser ablation of frozen Cl2: A possible neutral beam source for etching applications (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1146-1155 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge damage considerations are prompting the development of neutral beam sources for etching applications. Anisotropic etching with hyperthermal Cl2 and SF6 beams has been demonstrated. We describe a two-dimensional plasma chemistry fluid model of laser ablation of frozen Cl2 in vacuum as a neutral beam source. In this scheme an externally applied electric field would be used to enhance the dissociation rate of Cl2 potentially providing an enhanced Cl content in the beam for a greater etch rate. Laser ablation generated neutral beams also may contain a desirable and controllable ion content which may be used to further enhance the etch rate. Limitations of the concept are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362852
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  • 5
    Electronic Resource
    Electronic Resource
    T2 shortening in childhood moyamoya disease (1996)
    Springer
    Neuroradiology 38 (1996), S. S169 
    Details
    ISSN: 1432-1920
    Keywords: Moyamoya disease ; Cerebral infarction ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined T2 shortening in six children with infarcts due to moyamoya disease to clarify whether there are characteristic patterns of T2 shortening in the deep grey and white matter. Profound T2 shortening in the deep grey and white matter was observed in the acute stage of infarct in two cases, which changed to high intensity in the chronic stage; in this stage no T2 shortening was demonstrated in any case. Neither haemorrhagic infarction nor calcification was seen on CT or MRI. There could be longitudinally different T2 shortening patterns between infarcts due to moyamoya disease and other disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278150
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    T2 shortening in childhood moyamoya disease (1996)
    Springer
    Neuroradiology 38 (1996), S. S169 
    Details
    ISSN: 1432-1920
    Keywords: Key words Moyamoya disease ; Cerebral infarction ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined T2 shortening in six children with infarcts due to moyamoya disease to clarify whether there are characteristic patterns of T2 shortening in the deep grey and white matter. Profound T2 shortening in the deep grey and white matter was observed in the acute stage of infarct in two cases, which changed to high intensity in the chronic stage; in this stage no T2 shortening was demonstrated in any case. Neither haemorrhagic infarction nor calcification was seen on CT or MRI. There could be longitudinally different T2 shortening patterns between infarcts due to moyamoya disease and other disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050945
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    Paper (German National Licenses)
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