Radio-frequency plasma cleaning for mitigation of high-power microwave-pulse shortening in a coaxial gyrotron

Cohen, William E.; Gilgenbach, Ronald M.; Jaynes, Reginald L.; Peters, Christopher W.; Lopez, Mike R.; Lau, Y. Y.; Lau, Y.Y.; Anderson, Scott A.; Brake, Mary L.; Spencer, Thomas A.
December 2000
Applied Physics Letters;12/4/2000, Vol. 77 Issue 23
Academic Journal
Results are reported demonstrating that radio-frequency (rf) plasma cleaning is an effective technique for mitigating microwave-pulse shortening (i.e., lengthening the pulse) in a multimegawatt, large-orbit, coaxial gyrotron. Cleaning plasmas were generated by 50 W of rf power at 13.56 MHz in nitrogen fill gas in the pressure range 15-25 mTorr. Improvements in the averaged microwave energy output of this high-power-microwave device ranged from 15% to 245% for different initial conditions and cleaning protocols. The mechanism for this improvement is believed to be rf plasma sputtering of excess water vapor from the cavity/waveguide and subsequent removal of the contaminant by cryogenic vacuum pumps. © 2000 American Institute of Physics.


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