Download or read book Numerical Calculations Related to the Rf Properties of the Plasma Sheath written by John Milan Pavkovich and published by . This book was released on 1964 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: In many considerations of the rf properties of a finite plasma, the plasma is treated as a dielectric and the boundary conditions associated with an ordinary dielectric are applied. Although this approach works well at times, it is by no means a satisfactory approach to understanding the rf properties of the boundary. In this paper, a detailed rf theory of the sheath is presented. The complete collisionless Boltzmann equation is used to derive a linear integral equation for the rf electric field through the sheath. The analysis is one-dimensional. This integral equation is solved numerically for a semi-infinite uniform plasma bounded by a sheath defined by a parabolic dc potential. A Maxwellian distribution of velocities is assumed for all computations. The results show that it is reasonable to assume that the normal component of displacement is continuous but that extra waves are set up near the boundary which decay as one moves into the uniform plasma. These waves are somewhat like the cutoff waves excited in the neighborhood of a waveguide discontinuity and thus give rise to a sheath impedance. A pressure type theory is also presented. This theory is based on moments of the collisionless Boltzmann equation. The results do not agree very well with results of the more exact theory and thus it is concluded that this type of theory is rather unreliable. (Author).
Download or read book Numeral Calculations Related to the Rf Properties of the Plasma Sheath written by John Milan Pavkovich and published by . This book was released on 1964 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies of the Volume and Plasma Sheath Properties of Radio Frequency Discharges written by D. W. Ernie and published by . This book was released on 1988 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radio frequency discharges currently play a major role in the fabrication of microelectronic devices. This manuscript reports on theoretical and experimental studies undertaken in an effort to develop a better understanding of the underlying gas discharge physics occuring in these discharges. An equivalent circuit model was developed for a planar rf reactor based on the physical properties of the plasma sheath. This model shows that the waveforms of the potentials across the plasma sheaths are highly nonlinear and agree with previously reported measurements. These waveforms were subsequently incorporated into a model for the energy distribution of ions bombarding the electrode surfaces in low pressure rf reactors. Numerical calculations based on this model show the ion bombardment energy distribution is bimodal and skewed toward lower impact energies. Experimental measurements were also performed on the ion bombardment energy distribution in a planar rf reactor. The results of these measurements agree with the model predictions at low pressure and give information at higher pressures about the effects of collisions on the distribution, which agree with previous studies. The importance of negative ions in a discharge through an electronegative gas was investigated by the development of a collisionless plasma sheath model for such a discharge. A sheath criterion was derived and used to determine the effects of negative ions on the sheath properties.
Download or read book Numerical Analysis of Radio frequency Sheath plasma Interactions in the Ion Cyclotron Range of Frequencies written by Haruhiko Kohno and published by . This book was released on 2011 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electromagnetic plasma waves in the ion cyclotron range of frequencies (ICRF) are routinely used in magnetic fusion experiments to heat plasmas and drive currents. However, many experiments have revealed that wave energy losses in the plasma edge and at the wall are significant, and detected that the acceleration of ions into the walls due to the formation of radio-frequency (RF) sheaths is one of the root causes of this problem. Since the RF-enhanced sheaths have many undesirable effects, such as impurity production and hot spot generation, a predictive numerical tool is required to quantitatively evaluate these effects with complicated boundary shapes of tokamaks taken into account. In this thesis the numerical code that solves self-consistent RF sheath-plasma interactions in the scrape-off layer for ICRF heating is developed based on a nonlinear finite element technique and is applied to various problems in the one-dimensional (1D) and two-dimensional (2D) domains corresponding to simplified models for the poloidal plane of a tokamak. The present code solves for plasma waves based on the cold plasma model subject to the sheath boundary condition, in which the most important physics that happens in the sheath is captured without using the field quantities in the sheath. Using the developed finite element code, several new properties of the RF sheath plasma interactions are discovered. First, it is found in the 1D domain that multiple roots can be present due to the resonance of the propagating slow wave and its nonlinear interaction with the sheath. Second, sheath-plasma waves are identified in a 2D slab geometry, and it is proved in conjunction with an electrostatic 2D sheath mode analysis that the sheath-plasma wave only appears in the vicinity of the sheath surface if the plasma density is greater than the lower hybrid density, and its wavelength depends on various parameters. Third, as a consequence of the self-consistent interaction between the propagating slow wave and the sheath, it is shown that the electric field distribution pattern in the plasma smoothly varies along the magnetic field lines between the conducting-wall and quasi-insulating limits. In the numerical analysis employing the 2D domain whose scale is equivalent to the Alcator C-Mod device, it is demonstrated that the calculated sheath potential can reach the order of kV, which is sufficient to yield enhanced sputtering at the wall. In addition, it is shown that the sheath potential in the close vicinity of the antenna current strap can be insensitive to the direction of the background magnetic field in the RF sheath dominated regime. Further, it is found from a series of nonlinear calculations that the sheath potential sensitively varies depending on the plasma density and electron temperature, which is consistent with the scaling derived from the Child-Langmuir law and the definition of the RF sheath potential. Lastly, a new finite element approach, which is named the finite element wave-packet method, is developed for the purpose of solving for multiscale plasma waves in the tokamak poloidal plane accurately with reasonable computational cost. This method is established by combining the advantages of the finite element and spectral methods, so that important properties in the finite element method, such as the sparsity of the global matrix and the ease in satisfying the boundary conditions, are retained. The present scheme is applied to some illustrative 1D multiscale problems, and its accuracy improvement is demonstrated through comparisons with the conventional finite element method.
Download or read book RF Behavior of the Plasma Sheath written by John Milan Pavkovich and published by . This book was released on 1964 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical treatment for the variation of rf fields within the sheath is given. The analysis is based on an integration of the collisionless Boltzmann equation, assuming that the static potential varies parabolically in the sheath. An effective impedance for the sheath can be defined, and that over the range in which the numerical results have been calculated, this impedance always has a real positive part. The real part of this impedance is associated with Landau damping. A set of curves is given of the field through the sheath. (Author).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Research on Plasma Boundary Studies Final Report written by Stanford University. Microwave Laboratory and published by . This book was released on 1965 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Research written by United States. National Bureau of Standards and published by . This book was released on 1965 with total page 934 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Demand Bibliography written by and published by . This book was released on 1989 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Government Research Reports written by and published by . This book was released on 1964 with total page 2180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Research National Bureau of Standards written by United States. National Bureau of Standards and published by . This book was released on 1964 with total page 1400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radio Science written by and published by . This book was released on 1993 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book National Union Catalog written by and published by . This book was released on 1970 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes entries for maps and atlases.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1994-06 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The National Union Catalogs 1963 written by and published by . This book was released on 1964 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bibliography of Scientific and Industrial Reports written by and published by . This book was released on 1968-04 with total page 1070 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Annual Index of Reports for 1963 written by and published by . This book was released on 1964 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
