Distributed Ferrite Isolation in Traveling-Wave Tubes.
Final technical rept. Jun 74-May 76,
RAYTHEON CO WALTHAM MASS RESEARCH DIV
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This report presents the results of a two year program to demonstrate the feasibility of achieving wideband isolation in high power approximately 1 KW CW, 2 KW peak traveling-wave tubes. The program included cold test, analysis and hot test in one experimental tube. In attempting to achieve the widest band possible with TWTs, ferrite designs exploiting the existence of broadband edge modes were sought. This report describes the existence of two branches of such edge modes and evidence of coupling to at least one branch called the magnetostatic wave branch. Though somewhat restricted because of available space in the existing TWT QKW 1750 the final tube assembly showed the ability to produce over 40 dB reverse loss over an octave band. The designed isolation was wiped out, however, by an unanticipated effect of the axial focussing field in the completed tube. Hot tests showed reasonable beam focussing at above 50-100 percent higher than usual focussing current. No degradation of the samarium-cobalt magnet was observed after tube bakeout 400 C in vacuum. A program to achieve a theoretical understanding of ferrite slab modes and helix ferrite interaction is recommended. The results of such a theoretical study should permit a more successful realization of distributed isolation in TWTs. Author
- Electrical and Electronic Equipment