Improved analysis techniques for cylindrical and spherical double probes

Journal Article · Sun Jul 15 00:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4739221· OSTI ID:22093665

Beal, Brian; Brown, Daniel; Bromaghim, Daron ^[1]; Johnson, Lee ^[2]; Blakely, Joseph ^[3]

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1. Air Force Research Laboratory, 1 Ara Rd., Edwards Air Force Base, California 93524 (United States)
2. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, California 91109 (United States)
3. ERC Inc., 1 Ara Rd., Edwards Air Force Base, California 93524 (United States)

A versatile double Langmuir probe technique has been developed by incorporating analytical fits to Laframboise's numerical results for ion current collection by biased electrodes of various sizes relative to the local electron Debye length. Application of these fits to the double probe circuit has produced a set of coupled equations that express the potential of each electrode relative to the plasma potential as well as the resulting probe current as a function of applied probe voltage. These equations can be readily solved via standard numerical techniques in order to determine electron temperature and plasma density from probe current and voltage measurements. Because this method self-consistently accounts for the effects of sheath expansion, it can be readily applied to plasmas with a wide range of densities and low ion temperature (T{sub i}/T{sub e} Much-Less-Than 1) without requiring probe dimensions to be asymptotically large or small with respect to the electron Debye length. The presented approach has been successfully applied to experimental measurements obtained in the plume of a low-power Hall thruster, which produced a quasineutral, flowing xenon plasma during operation at 200 W on xenon. The measured plasma densities and electron temperatures were in the range of 1 Multiplication-Sign 10{sup 12}-1 Multiplication-Sign 10{sup 17} m{sup -3} and 0.5-5.0 eV, respectively. The estimated measurement uncertainty is +6%/-34% in density and +/-30% in electron temperature.

• OSTI ID: 22093665
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 7; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CYLINDRICAL CONFIGURATION
DEBYE LENGTH
DENSITY
ELECTRON TEMPERATURE
EXPANSION
ION TEMPERATURE
IONS
LANGMUIR PROBE
OPERATION
PLASMA
PLASMA DENSITY
PLASMA POTENTIAL
SPHERICAL CONFIGURATION
THRUSTERS
XENON