Chapter 39. Tunable TM010 Mode Cavity with Variable Coupling for Microwave Processing of Low-Loss Materials

  1. John B. Wachtman Jr.
  1. Hardial S. Dewan1,
  2. Morris E. Brodwin2 and
  3. D. Lynn Johnson2

Published Online: 28 MAR 2008

DOI: 10.1002/9780470314050.ch39

A Collection of Papers Presented at the 94th Annual Meeting and the 1992 Fall Meeting of the Materials & Equipment/Whitewares Manufacturing: Ceramic Engineering and Science Proceedings, Volume 14, Issue 1/2

A Collection of Papers Presented at the 94th Annual Meeting and the 1992 Fall Meeting of the Materials & Equipment/Whitewares Manufacturing: Ceramic Engineering and Science Proceedings, Volume 14, Issue 1/2

How to Cite

Dewan, H. S., Brodwin, M. E. and Johnson, D. L. (1993) Tunable TM010 Mode Cavity with Variable Coupling for Microwave Processing of Low-Loss Materials, in A Collection of Papers Presented at the 94th Annual Meeting and the 1992 Fall Meeting of the Materials & Equipment/Whitewares Manufacturing: Ceramic Engineering and Science Proceedings, Volume 14, Issue 1/2 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314050.ch39

Author Information

  1. 1

    Materials Research Laboratory Pennsylvania State University University Park, PA 16802

  2. 2

    Northwestern University Evanston, IL 60201

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1993

ISBN Information

Print ISBN: 9780470375235

Online ISBN: 9780470314050

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Keywords:

  • variable coupling;
  • microwave processing;
  • sapphire tubes;
  • mechanical system;
  • microwave heating systems

Summary

Materials having a low loss factor are very difficult to heat by microwaves, more so when they are in the form of thin rods, filaments, or tubes. This paper describes a TM010 mode cavity with a demountable coupling aperture that forms a smooth transition into the cavity and the radio frequency field inside. TM010 mode cavity cannot be easily tuned because its resonant frequency, f0, depends on the diameter of the cavity and not on its length. To compensate for changes of f0 with material dimensions, the dielectric constant, and its variations with temperature, two sapphire tubes are symmetrically moved in and out at the cavity axis. A tuning range of 145 MHz has been attained. The unloaded Q0 of the cavity is 4500, which indicates low cavity losses and a high field concentration at the axis. A uniform hot zone of about 1 in. length is produced on the axially placed sample of an alumina composite with an average rate of rise of temperature of over 20°C/s, using a 1-kW, 2 45-GHz generator.