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Title: On steady flows in smooth-walled magnetrons: Fundamental modes and no-cutoff flows in planar geometry

Abstract

The Maxwell equations coupled with the ideal fluid equations for a warm isothermal non-neutral plasma are applied without approximation to predict three modes of time-independent electron flow in smooth-walled planar magnetrons, at any temperature. For all three modes, the equations predict that the fluid flow velocity tangent to the cathode is the Brillouin velocity. One of the modes is the well-known magnetic insulation mode, in which the magnetic field is larger than the Hull cutoff field [Phys. Rev. 18, 31 (1921)], the anode current is essentially zero, and virtually all the electrons reside in a sheath near the cathode. The other two modes exhibit fairly large anode currents. One of these modes is the well-known Child-Langmuir flow [Phys. Rev. 32, 492 (1911); ibid. 21, 419 (1923)], in which the magnetic field is smaller than the Hull cutoff field. The other high-current mode, in which the magnetic field is larger than the Hull cutoff field, has not been discussed previously; in this paper, it is called the 'no-cutoff' (NC) mode. Experiments using a thin smooth-walled magnetron were conducted, during which large anode currents were observed even for magnetic fields much larger than the Hull cutoff field. It is shown that NCmore » mode parameters can be adjusted to produce a complete agreement with the experimental results, but that this requires the transverse flow velocity near the cathode to be superthermal and even mildly relativistic for the larger magnetic fields. Matching the experimental values also predicts a number density that is larger near the anode than near the cathode, but is small enough that space-charge effects are negligible in most cases.« less

Authors:
; ; ;  [1];  [2];  [3]
  1. Physics Department, New Mexico State University, Las Cruces, New Mexico 88003 (United States)and Raytheon Missile Systems, 1151 E. Hermans Road, Tucson, Arizona 85706 (United States)
  2. (United States) and Raytheon Missile Systems, 1151 E. Hermans Road, Tucson, Arizona 85706 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
20782359
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 12; Journal Issue: 11; Other Information: DOI: 10.1063/1.2122427; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANODES; APPROXIMATIONS; CATHODES; CHARGED-PARTICLE TRANSPORT; ELECTRIC CURRENTS; ELECTRON TEMPERATURE; ELECTRONS; GEOMETRY; IDEAL FLOW; ION TEMPERATURE; MAGNETIC FIELDS; MAGNETIC INSULATION; MAGNETRONS; MAXWELL EQUATIONS; PLASMA DENSITY; PLASMA INSTABILITY; PLASMA SHEATH; RELATIVISTIC PLASMA; RELATIVISTIC RANGE; SPACE CHARGE

Citation Formats

Goedecke, G.H., Davis, Brian T., Chen Chiping, Baker, C. Vincent, Intense Beam Theoretical Research Group, Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Raytheon Missile Systems, 1151 E. Hermans Road, Tucson, Arizona 85706. On steady flows in smooth-walled magnetrons: Fundamental modes and no-cutoff flows in planar geometry. United States: N. p., 2005. Web. doi:10.1063/1.2122427.
Goedecke, G.H., Davis, Brian T., Chen Chiping, Baker, C. Vincent, Intense Beam Theoretical Research Group, Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, & Raytheon Missile Systems, 1151 E. Hermans Road, Tucson, Arizona 85706. On steady flows in smooth-walled magnetrons: Fundamental modes and no-cutoff flows in planar geometry. United States. doi:10.1063/1.2122427.
Goedecke, G.H., Davis, Brian T., Chen Chiping, Baker, C. Vincent, Intense Beam Theoretical Research Group, Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Raytheon Missile Systems, 1151 E. Hermans Road, Tucson, Arizona 85706. Tue . "On steady flows in smooth-walled magnetrons: Fundamental modes and no-cutoff flows in planar geometry". United States. doi:10.1063/1.2122427.
@article{osti_20782359,
title = {On steady flows in smooth-walled magnetrons: Fundamental modes and no-cutoff flows in planar geometry},
author = {Goedecke, G.H. and Davis, Brian T. and Chen Chiping and Baker, C. Vincent and Intense Beam Theoretical Research Group, Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and Raytheon Missile Systems, 1151 E. Hermans Road, Tucson, Arizona 85706},
abstractNote = {The Maxwell equations coupled with the ideal fluid equations for a warm isothermal non-neutral plasma are applied without approximation to predict three modes of time-independent electron flow in smooth-walled planar magnetrons, at any temperature. For all three modes, the equations predict that the fluid flow velocity tangent to the cathode is the Brillouin velocity. One of the modes is the well-known magnetic insulation mode, in which the magnetic field is larger than the Hull cutoff field [Phys. Rev. 18, 31 (1921)], the anode current is essentially zero, and virtually all the electrons reside in a sheath near the cathode. The other two modes exhibit fairly large anode currents. One of these modes is the well-known Child-Langmuir flow [Phys. Rev. 32, 492 (1911); ibid. 21, 419 (1923)], in which the magnetic field is smaller than the Hull cutoff field. The other high-current mode, in which the magnetic field is larger than the Hull cutoff field, has not been discussed previously; in this paper, it is called the 'no-cutoff' (NC) mode. Experiments using a thin smooth-walled magnetron were conducted, during which large anode currents were observed even for magnetic fields much larger than the Hull cutoff field. It is shown that NC mode parameters can be adjusted to produce a complete agreement with the experimental results, but that this requires the transverse flow velocity near the cathode to be superthermal and even mildly relativistic for the larger magnetic fields. Matching the experimental values also predicts a number density that is larger near the anode than near the cathode, but is small enough that space-charge effects are negligible in most cases.},
doi = {10.1063/1.2122427},
journal = {Physics of Plasmas},
number = 11,
volume = 12,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}