Comment on 'Power loss in open cavity diodes and a modified Child-Langmuir law' [Phys. Plasmas 12, 093102 (2005)]

Journal Article · Sat Sep 15 04:00:00 EDT 2007 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2761862· OSTI ID:21069862

Swanekamp, S B; Ottinger, P F ^[1]

---

1. Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

In this Comment, it is shown that no modification of the Child-Langmuir law [Phys. Rev.32, 492 (1911); Phys. Rev. 2, 450 (1913)] is necessary to treat the space-charge-limited flow from a diode with an open boundary as reported in Phys. Plasmas 12, 093102 (2005). The open boundary condition in their simulations can be represented by a voltage source and a resistor whose value is the vacuum-wave impedance of the opening. The diode can be represented as a variable resistor whose value depends on the voltage drop across the diode (as measured by the line integral of E across the diode gap). This is a simple voltage-divider circuit whose analysis shows that the real diode voltage drops as the vacuum-wave impedance increases. Furthermore, it is shown that in equilibrium, the voltage drop between the anode and cathode is independent of the path chosen for the line integral of the electric field so that E=-{nabla}{phi} is valid. In this case, the equations of electrostatics are applicable. This clearly demonstrates that the electric field is electrostatic and static fields DO NOT RADIATE. It is shown that the diode voltage drops as the vacuum wave impedance increases and the current drops according to the Child-Langmuir law. Therefore, the observed drop in circuit current can be explained by a real drop in voltage across the diode and not an effective drop as claimed by the authors.

• OSTI ID: 21069862
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 14; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANODES
BOUNDARY CONDITIONS
CATHODES
COMPUTERIZED SIMULATION
ELECTRIC CURRENTS
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ELECTROSTATICS
IMPEDANCE
PLASMA
POWER LOSSES
RESISTORS
SPACE CHARGE
VOLTAGE DROP