Intense electron-beam ionization physics in air

Strasburg, Sean; Hinshelwood, D.D.; Schumer, J.W.; Mosher, D.; Ottinger, P. F.; Fernsler, R. F.; Slinker, S. P.

doi:10.1063/1.1600737

Cited by 14 publications

(8 citation statements)

References 69 publications

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“…Propagation of the electron beam through fully ionized plasmas has been studied for several decades [3]. However, relatively few studies investigating the ionization dynamics of neutral materials have been reported [4][5][6][7][8].A high current density electron beam propagated through a neutral material can generate a large electrostatic field owing to the effect of charge nonneutrality. The large electrostatic field can directly ionize the neutral material, a process referred to as field ionization [9].…”

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Role of Field and Electron Impact Ionization in Ionization Front Generated by an Intense Electron Beam

Katō

Kishimoto

Takahashi

et al. 2012

Plasma and Fusion Research

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The interaction of an intense electron beam with a neutral background material is studied. The neutral material is ionized by the electrostatic field generated by the intense electron beam and electron impact ionization. The structure of the ionization front is analyzed using a one-dimensional model. The structure is determined primarily by electron impact ionization of the ionized background electrons. In addition, the field ionization contributes to the generation of the ionization front by increasing the density of the electron beam. An intense electron beam can be efficiently generated by intense short laser pulses. One particular application for this is energetic ion sources using thin foils [1,2]. In this regard, the understanding of the dynamics of the electron beam is crucial. Propagation of the electron beam through fully ionized plasmas has been studied for several decades [3]. However, relatively few studies investigating the ionization dynamics of neutral materials have been reported [4][5][6][7][8].A high current density electron beam propagated through a neutral material can generate a large electrostatic field owing to the effect of charge nonneutrality. The large electrostatic field can directly ionize the neutral material, a process referred to as field ionization [9]. Furthermore, the field enhances impact ionization by the background electrons. However, once a plasma is created, it strongly screens the electrostatic field. The ionization processes and electrostatic field screening significantly affect the properties of the plasma.In this paper, the structure of the ionization front in the direction of the initial electron beam propagation is studied using a one-dimensional stationary model, and the role of the ionization processes is clarified. We assumed that the electron motion is separated by the components of the ionized background and input high-energy beam electrons. The density of the background electrons is usually much higher than that of the high-energy electron beam. We assumed that the background electron motion is described by electron fluid equations and that the atom only changes the charge states. The density profile of an electron beam does not change, and its energy b is constant; that is, the author's e-mail: s.kato@aist.go.jp beam only propagates under the same initial density n b and velocity u b . Thus, the evolution of the density of a background electron n e and that of an ion n i are described bywhere N and ν I are density and ionization rate of the atom, respectively, and u d is the electron fluid velocity, which is determined by u d = −eE/m e ν e , where E is the electrostatic field, e and m e are the electron charge and mass, respectively, and ν e is the electron collision frequency of a background electron. The electron collision frequency and ionization rate are dependent on the type of material and the density and strength of the electric field. In this model, the ionization rate ν I is assumed to consist of contributions from the electric field and electron impa...

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confidence: 99%

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Role of Field and Electron Impact Ionization in Ionization Front Generated by an Intense Electron Beam

Katō

Kishimoto

Takahashi

et al. 2012

Plasma and Fusion Research

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“…The predecessor to this model [4] assumed an undissociated gas with singlyionized molecules, and used the localrfield approximation for the electron temperature, so that T,…”

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“…A ring-diode experiment [4] used a twocolor interferometer to analyze the effects of a 140 ns annular electron beam, extending from 6.5 to 7.5 cm radius, transporting 800 kA at 900 kV through 1 to IO Ton air. In a second experiment, a paraxial diode generated a 30 U, 1.4 M v electron beam whose effects in air, argon and helium were studied.…”

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confidence: 99%

“…The gas-physics method described here extends an earlier LSPI31 scalar conductivity swarm model which was compared to experiment through theory and computation [4]. In the present model, rate equations for three molecular species and all atomic charge states are solved simultaneously with two energy balance equations to determine the temperatures of electrons and heavy particles.…”

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Strongly-perturbed non-equilibrium gas physics model for the paraxial diode transport cell

Strasburg

Hinshelwood

Mosher

et al.

Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference (IEEE Cat. No.03CH37472)

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Intense short-pulse charged-particle beam-those with tens or hundreds of kA/cm2 and beam risetimes less than 100 ns-can disturb the background gas so severely that not only are diatomic molecules ionized, but molecules may be dissociated and the product atoms themselves multiply ionized. Such beam-background systems are generally far from temperature and species equilibrium. The plasma conductivity 0, which is determined by the degree of ionization and the species temperatures, strongly influences the beam behavior through the plasma return current. Thus, simultaneously and self-consistently solving for both o and the beam propagation is essential for a correct description of the system behavior. A plasma physics model with advanced gas chemistry has been developed and incorporated into the simulation code LSP to help meet this objective.

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On intense electron beam propagation through gas jets

Krasheninnikov

Frolov

2006

Physics of Plasmas

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The structure of the ionization front created by an expanding high-intensity electron beam as it travels through ∼1atm gas is considered theoretically. The velocity of the front, Vf, on the order of a few 10∧9cm∕s, is determined by the electric field ionization process. When decreasing the gas density, the velocity Vf decreases relatively slowly up to some threshold, after which it starts rapidly falling. The magnitude of Vf is higher for argon than for helium. These findings are supported by experimental observations.

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Intense electron-beam ionization physics in air

Cited by 14 publications

References 69 publications

Role of Field and Electron Impact Ionization in Ionization Front Generated by an Intense Electron Beam

Role of Field and Electron Impact Ionization in Ionization Front Generated by an Intense Electron Beam

Strongly-perturbed non-equilibrium gas physics model for the paraxial diode transport cell

On intense electron beam propagation through gas jets

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