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1 Mar 2006

Volume 99, Issue 5, Articles (05xxxx)

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Ablation study in the capillary discharge of an electrothermal gun

Michael Keidar and Iain D. Boyd

J. Appl. Phys. 99, 053301 (2006); http://dx.doi.org/10.1063/1.2174111 (7 pages) | Cited 14 times

Online Publication Date: 1 March 2006

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In this paper, we study the ablation phenomena associated with the operation of a capillary discharge for an electrothermal gun. Electrothermal-chemical (ETC) guns are used for enhancement of ignition and combustion of an energetic propellant. One of the major components of the ETC system is a plasma source based on a capillary discharge. In this paper, a model of the capillary discharge is developed. In this model, primary attention is paid to the ablation phenomenon. Different characteristic subregions near the ablated surface, namely, a space-charge sheath, a Knudsen layer, and a hydrodynamic layer, are considered. In this formulation, the ablation rate is determined by the parameters at the edge of the Knudsen layer. The kinetic approach is used to determine the parameters at the interface between the kinetic Knudsen layer and the hydrodynamic layer. Coupling the solution of the nonequilibrium Knudsen layer with the hydrodynamic layer provides a self-consistent solution for the ablation rate. According to the model predictions, the peak electron temperature is about 1.4 eV, the polyethylene surface temperature is about 700 K, and the pressure is about 10 MPa. It is found that the ablation rate increases with the capillary length. The ablated mass and the predicted total pressure agree with previous experimental observations.
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52.80.-s Electric discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.33.Vx Reactions in flames, combustion, and explosions
52.50.Dg Plasma sources
52.40.Hf Plasma-material interactions; boundary layer effects
52.40.Kh Plasma sheaths

Optical emission spectroscopy of metal-halide lamps: Radially resolved atomic state distribution functions of Dy and Hg

T. Nimalasuriya, A. J. Flikweert, W. W. Stoffels, M. Haverlag, J. J. A. M. van der Mullen, and N. B. M. Pupat

J. Appl. Phys. 99, 053302 (2006); http://dx.doi.org/10.1063/1.2175466 (7 pages) | Cited 15 times

Online Publication Date: 2 March 2006

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Absolute line intensity measurements are performed on a metal-halide lamp. Several transitions of atomic and ionic Dy and atomic Hg are measured at different radial positions from which we obtain absolute atomic and ionic Dy intensity profiles. From these profiles we construct the radially resolved atomic state distribution function (ASDF) of the atomic and ionic Dy and the atomic Hg. From these ASDFs several quantities are determined as functions of radial position, such as the (excitation) temperature, the ion ratio Hg+/Dy+, the electron density, the ground state, and the total density of Dy atoms and ions. Moreover, these ASDFs give us insight about the departure from equilibrium. The measurements show a hollow density profile for the atoms and the ionization of atoms in the center. In the outer parts of the lamp molecules dominate.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Jm Ionization of plasmas
52.25.Fi Transport properties

Floating potential and sheath thickness for cylindrical and spherical probes in electronegative plasmas

R. Morales Crespo, J. I. Fernández Palop, M. A. Hernández, S. Borrego del Pino, J. M. Díaz-Cabrera, and J. Ballesteros

J. Appl. Phys. 99, 053303 (2006); http://dx.doi.org/10.1063/1.2179137 (6 pages) | Cited 11 times

Online Publication Date: 13 March 2006

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In this paper, the floating potential, for cylindrical and spherical Langmuir probes immersed into an electronegative plasma, is determined by using a radial model described in a previous paper. This floating potential is determined for several probe radius values and ranks of plasma electronegativity, from almost electropositive plasmas to high electronegative plasmas. The thickness of the positive ion sheath is also determined for this kind of probes in electronegative plasmas, as well as the analytical expressions fitting this thickness, showing its dependence on the probe radius and electric potential.
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52.70.Ds Electric and magnetic measurements
52.40.Kh Plasma sheaths
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