A New Type of High-Frequency Amplifier

N CENTIMETER range amplifiers involving electromagnetic resonators or transmission circuits as, in klystrons and conventional traveling-wave tubes, it is desirable to have the electron flow very close to the metal circuit elements, where the radio-frequency field, of the circuit is strong, in order to obtain satisfactory amplification. It is, however, difficult to confine the electron flow close to metal circuit elements without an interception of electrons, which entails both loss of efficiency and heating of the circuit elements. This latter may be extremely objectionable at very short wavelengths for whirh circuit elements are small and fragile. In this paper the writers describe a new type of amplifier. In this amplifier the gain is not obtained through the interaction of electrons with the field of electromagnetic resonators, helices or other circuits. Instead, an electron flow consisting of two streams of electrons having different average velocities is used. When the currents or charge densities of the two streams are sufficient, the streams interact so as to give an increasing wave. Electromagnetic circuits may be used to impress a signal on the electron flow, or to produce an electromagnetic output by means of the amplified signal present in the electron flow. The amplification, however, takes place in the electron flow itself, and is the result of what may be termed an electromechanical interaction.1,2 While small magnetic fields are necessarily present because of the motions of the electrons, these do not play an important part in the amplification.