A high-efficiency quasi-optical mode converter for whispering gallery mode gyrotrons

M. Blank

doi:10.1117/12.2297848

1 October 1991 A high-efficiency quasi-optical mode converter for whispering gallery mode gyrotrons

M. Blank

Proceedings Volume 1576, 16th International Conference on Infrared and Millimeter Waves; 15763R (1991) https://doi.org/10.1117/12.2297848
Event: 16th International Conference on Infrared and Millimeter Waves, 1991, Lausanne, Switzerland

Abstract

A mode converter for whispering gallery mode gyrotrons has been designed and experimentally demonstrated to have 95% calorimetric efficiency. Experiments were performed on a megawatt power level, 3μs pulsed gyrotron operating in the TE_16,2,1 whispering gallery mode at 146 GHz. The gyrotron cavity employs a nonlinear uptaper to minimize radial mode conversion. About 97% of the output power is in the TE_16,2 mode. A doubly curved reflector, designed using ray optics and vector diffraction theory, was recently built to focus the full radiation pattern. Experiments show that the converter focuses at least 92% of the incident radiation into a Gaussian-like TE_16,2 focal spot, about 1.5 cm in width. Small fractions of other spatial modes were found to form focal spots in the far field. Analysis of the power in the other focal spots allows for a good quantitative measurement of the gyrotron output mode content, potentially on a single shot basis.

Citation Download Citation

M. Blank "A high-efficiency quasi-optical mode converter for whispering gallery mode gyrotrons", Proc. SPIE 1576, 16th International Conference on Infrared and Millimeter Waves, 15763R (1 October 1991); https://doi.org/10.1117/12.2297848

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