Relationship Between the Number Density and the Phase Shift in Microwave Interferometry for Atmospheric Pressure Plasmas

  • Mounir Laroussi


Diagnosing atmospheric pressure discharges requires more sophisticated techniques than for low pressure plasmas. The plasma number density is a crucial parameter in several applications. Langmuir probe as a number density measuring technique is not applicable at high pressures because the electron mean free path is shorter than the Debye distance. Microwave interferometry appears to be an effective diagnostic technique in this case. However, because of the high collisionality of atmospheric pressure plasmas, the relationship between the phase shift, as measured by a microwave interferometer, and the plasma number density is not straightforward, as is the case in collisionless plasmas. For the special case of a uniform discharge, the plasma number density is found to depend on the square root of the phase shift.


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  1. [1]
    S. Kanazawa, M. Kogoma, T. Moriwaki, and S. Okazaki, “Stable Glow Plasma at Atmospheric Pressure“, J. Phys. D: Appl. Phys., 21, 839, (1988).Google Scholar
  2. [2]
    F. Massines, C. Mayoux, R. Messaoudi, A. Rabehi, and P. Segur, “Experimental Study of an Atmospheric Pressure Glow Discharge: Application to Polymers Surface Treatment“, In Proc. 1992 Int. Conf. Gas Discharges & their Applications, 730, (1992).Google Scholar
  3. [3]
    M. Laroussi, “Sterilization of Contaminated Matter with an Atmospheric Pressure Plasma“, IEEE Trans. Plasma Sci., 24, 1188, (1996).Google Scholar
  4. [4]
    R. Block, M. Laroussi, and K. Schoenbach, “Test Facility for High Pressure Plasmas“, In Proc. 1999 IEEE Int. Conf. Plasma Sci., (1999).Google Scholar
  5. [5]
    M. A. Heald, and C. B. Wharton, “Plasma Diagnostics with Microwaves“, Krieger Pub., New York, (1978).Google Scholar
  6. [6]
    M. Laroussi, “Interaction of Microwaves with Atmospheric Pressure Plasmas”, Int. J. Infrared and Millimeter Waves, 16, 2069, (1995).Google Scholar
  7. [7]
    E. Koretzky, and S. P. Kuo, “Characterization of an Atmospheric Pressure Plasma Generated by a Plasma Torch Array“, Phys. Plasmas, 5, 3774, (1998).Google Scholar
  8. [8]
    R. J. Vidmar, “On the Use of Atmospheric Pressure Plasmas as Electromagnetic Reflectors and Absorbers“, IEEE Trans. Plasma Sci., 18, 733, (1990).Google Scholar
  9. [9]
    M. Laroussi, and W. T. Anderson, “Attenuation of Electromagnetic Waves by a Plasma Layer at Atmospheric Pressure”, Int. J. Infrared and Millimeter Waves, 19, 453, (1998).Google Scholar

Copyright information

© Plenum Publishing Corporation 1999

Authors and Affiliations

  • Mounir Laroussi
    • 1
  1. 1.Applied Research CenterOld Dominion UniversityNewport NewsVirginia

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