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  • 1
    Electronic Resource
    Electronic Resource
    Ion dynamics in the sheath in multicomponent plasma with negative ions (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 2733-2736 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Observations on steady state ion-rich sheath around a negatively biased grid in a double plasma device have been made in multicomponent plasma with negative ions. A hump in the potential profile is found to occur at the sheath edge. The characteristics of the hump depend on the grid voltage, source biasing voltage, density difference in the two chambers, and the negative to positive ion concentration ratio. It is argued that resonance which is coupled with the beam ions and background ions is associated in the excitation mechanism to create the nonsymmetrical structures in the plasma potential profile. Below the critical concentration ratio, the hump grows in height and above the critical ratio, the width of the hump increases but the height decreases and ultimately it vanishes. The variation in the hump potential profile due to the injection of negative ions can be explained by the ion momentum exchange and by their dynamics. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150683
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  • 2
    Electronic Resource
    Electronic Resource
    Characteristic behavior of the sheath formation in thermal plasma (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3685-3689 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma sheath equation, based on the quasipotential analysis, has been derived in a plasma taking finite ion temperature into account with a view to showing the characteristic behavior of the sheath formation in front of the electron absorbing wall. The derived Sagdeev potential equation, under small amplitude approximation, describes the Bohm sheath criterion, which enables one to find the required condition for the formation of sheath in plasmas. Later, the sheath equation is completely solved numerically by using the fourth-order Runge–Kutta method to yield the characteristic features of the potential variation in the sheath region. The main goal is to determine the sheath thickness and the potential variation in the sheath region and to compare the variation with those in cold ion plasma. Again, in the higher potential region, an improved Child's law has been derived and the potential variation has been estimated numerically, which shows that the improved Child's law improves the results as compared to that by Child's law. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873627
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  • 3
    Electronic Resource
    Electronic Resource
    Observations of low-frequency mode in a multicomponent plasma with negative ions (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1636-1640 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Based on linear perturbation theory, a dispersion relation for low-frequency (LF) electrostatic waves has been derived in a multicomponent plasma containing negative ions. To relate the theoretical observations with experiments on the LF wave, the slower mode has been studied extensively for various plasma models. The experiment was carried out in Ar, F, and electron plasma in a double plasma device. The experimental observations on LF electrostatic waves yield the qualitative frequency variations due to the presence of negative ions. In the region of lower negative ion concentration, the mode decreases with the addition of a higher percentage of negative ion concentration while later, in the higher region of negative ion concentration, the variation shows the asymptotic behavior with negative ion concentration. Both the observations, theoretical and experimental, have shown a good agreement with each other. Moreover, a theoretical model of plasma with heavy negative ions has also been presented. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873418
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  • 4
    Electronic Resource
    Electronic Resource
    Characteristics of sheath instability in a double plasma device (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 61-68 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Observations are carried out in a double-plasma device where the instabilities are excited around the negatively biased grid when there is sufficient plasma density difference between the two chambers and an ion beam is injected from the source to the target section. If the density difference between the two chambers is slowly decreased, the instabilities exhibit oppositely different characteristics after a critical value. Below the critical value of the density ratio, the energy resonance of the background ions and the beam ions is a typical condition for the excitation of such instabilities. Chaotic phenomena occur when there is a hump in the plasma potential profile near the sheath edge. Above the critical value of the density ratio, the instability occurs due to the interaction of the three beams that arise due to asymmetry of the sheath potential. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872111
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  • 5
    Electronic Resource
    Electronic Resource
    Observation of beam-enhanced sheath instability in a double plasma device (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3245-3250 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of ion beams on sheath properties are experimentally investigated in a double plasma device. The dispersion relations of the ion beam plasmas are measured by interferometer method. The low-frequency instability due to sheath around the negatively biased grid is found to be controlled by two parameters, namely the grid biasing voltage and source anode biasing voltage. The instability is caused by the resonant coupling of the three ion beams that arise due to asymmetry of the sheath potential. The sheath structure follows the Child–Langmuir law and the frequency of the instability is also found to be inversely proportional to the sheath thickness. Therefore, the transit time model is considered to explain the observed phenomena. The coupling between the beam and the oscillating component of the ions through the sheath enhances the instability growth which occurs mainly in the presheath region. The excitation of the instability occurs within certain range of velocity ratio of different beam modes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871607
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental observation of sheath and magnetic presheath over an oblique metallic plate in the presence of a magnetic field (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 683-690 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental observation on sheath and magnetic presheath over an oblique metallic plate in the presence of a magnetic field has been performed. The plate has been deployed in the plasma environment, making some finite angle with the externally applied magnetic field. Studies have been carried out for various angles, magnetic field gradients and plate-biasing voltages as well. The analyses reveal that the magnetic presheath thickness increases while the angle is varied from minimum to maximum; whereas the reverse happens in case of the sheath thickness. Furthermore, measurements of the sheath widths with increasing magnetic field strengths and the plate biasing voltages have been done which imply that sheath width enhances with increasing both the parameters. The electron temperature in the bulk plasma region is also evaluated for all the plasma conditions so as to find out its influence on the characteristic behavior of the sheath formation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1431973
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of magnetic field on plasma sheath and electron temperature (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 2282-2287 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experimental observation has been carried out to see the effect of magnetic field and grid biasing voltage in controlling the sheath thickness in a magnetized plasma system. The experiment is carried out in a stainless steel chamber which is divided into two regions by a mesh grid, via the source region and the diffused region. The characteristic behavior of the ion rich sheath formed across the grid under various conditions of the applied magnetic field and grid biasing voltage has been investigated experimentally. It has been observed that at both conditions of increasing magnetic field and grid biasing voltage, sheath width expands in the source region, whereas in the diffused region, no such noticeable variation has been found. This study has been accompanied by the measurement of the electron temperature in both regions of the chamber via the source region and the diffused region with the help of the Langmuir probe. Plasma is produced in the source region and it penetrates into the diffused region through the grid. It has been found that the electron temperature decreases with increasing magnetic field in the source region while kept at a constant grid biasing voltage. However, in the diffused region the opposite variation has been observed. The variation of electron temperature with grid biasing voltage in both regions is not very significant. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362437
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