The dimensional controls which must be imposed in the design and fabrication of parallel-operating, wide bandwidth EHF TWTs are examined. These controls were applied to build a group of 20 W, 18-40 GHz tubes, data for which are reported. INTRODUCTlONDesigning an octave bandwidth traveling wave tube for phase and gain matched operation in the EHF region presents several obstacles. In addition to devising means for fabricating the small helix and reducing its velocity dispersion across the wide operating range, the designer must control the dimensional tolerances of the helix and of the assembled tube with a high degree of precision to keep the tube to tube variations within the limits required for parallel tube operation. Table 1 shows the electrical phase and gain deviation limits specified for an application utilizing multiple tubes operating in parallel from a common voltage source.

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A theory of acoustic scattering of light in a Fabry-Perot resonator is described. The theory predicts the optimum acoustic scattering frequencies, the cavity geometry. The calculation is based on the formalism developed by the acoustic bandwidth, and the scattering enhancements as a function of ments are discussed which yield results in excellent agreement with the Gordon and Rigden for the Fabry-Perot Electro-optic Modulator. Experitheory. Acoustic phase velocities can be determined to 4-place accuracy.can be made to produce 100% amplitude modulation with acoustic powers lessThe experiments illustrate that narrowband modulators ( W 10 mc/s) than 50 milliwatts. Session 12: Microwave Tubes /I -Crossed Field DevicesThursday, Oct. 21, 2:OO to 5:OO p.m.

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