. The Bell System technical journal . gain arisingfrom the interaction between two streams of electrons is clear, and that thebroad frequency response predicted by the theory has been confirmed. 2. Description or Amplifier The frequency range near 200 Mc was chosen for the first experimentaltest of the proposed method of amplification for reasons of theory indicates that current density requirements increase with fre-quency, but that these requirements become severe only at the higher micro-wave frequencies. Availability of circuit parts and test equipment, ratherthan anticipat
. The Bell System technical journal . gain arisingfrom the interaction between two streams of electrons is clear, and that thebroad frequency response predicted by the theory has been confirmed. 2. Description or Amplifier The frequency range near 200 Mc was chosen for the first experimentaltest of the proposed method of amplification for reasons of theory indicates that current density requirements increase with fre-quency, but that these requirements become severe only at the higher micro-wave frequencies. Availability of circuit parts and test equipment, ratherthan anticipated difficulties at higher frequencies, led to the choice that wasmade. The essential features of one of the double-stream amplifier tubes whichhas been constructed and operated are represented in Fig. 1. The out-put helix was identical with the input helix in construction and connection 1A New Type of High Frequency Amplifier, J. R. Pierce and W. B. Hebenstreit, thisissue of the B. S. T. J. 52 INTERACTION BETWEEN ELECTRON STREAMS 53. 54 BELL SYSTEM TECHNICAL JOURNAL to the coaxial line. The two identical probes pi, and p2 , extending fromcoaxial lines into the two electron streams at the beginning and end of thecentral portion of the tube between the two helices were inserted for com-parison of the signal amplitudes at the be;.^innini? and end of the region inwhich no circuit is present. A similar tube containing an output gap in place of the output helix sec-tion is represented in Fig. 2. In both cases concentric tubular electron streams originate at the ring-shaped emitting surfaces of the two cathodes at potentials Vi and V2, passthrough their respective control grids and through a common acceleratinggrid. An axial magnetic field of approximately 700 gauss is applied in orderto maintain the definition of the beams. The outer and inner tubular beams
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