External RF Signal Research Articles

Operation and theory of a driven single-mode electron cyclotron maser.

A study is made of the operation of the electron cyclotron resonance maser (ECRM), when subjected to an external rf signal. The signal is introduced both via direct injection through a coupling hole in the oscillator and by modulating the electron beam in separate cavities, upstream of the oscillator. Experiments using both one and two ``prebunching'' cavities are reported. It is experimentally found that the gyromonotron, a specific embodiment of the ECRM, can be phase locked by premodulating the electron beam at drive power levels more than two orders of magnitude below that predicted by Adler's widely applicable theory for single-cavity oscillators. A perturbation theory is used to predict the phase-locking frequency band for a gyromonotron with any number of prebunching cavities. The predictions of this theory agree with the experimental results for two- and three-cavity phase locking. An investigation is made into the general amplitude and frequency response of the ECRM to an applied external signal. Experimentally, three distinct regions of qualitatively different ECRM behavior are noted: soft excitation, which is free, self-excited oscillation; hard excitation, where the oscillation requires an external impulse for startup; and amplifier, in which the output power level and frequency are linearly related to the drive in the small-signal regime.

Suppression of beam excited ion-acoustic noise by an externally applied RF signal

Ion-acoustic noise with a broad spectrum is suppressed by an external RF signal. Deformation of the ion energy distribution accompanies the suppression.

Analogue simulation of Josephson junction with linear-periodic current-phase relation

It is shown that an RCL sweep oscillator can serve as a simple analogue of a Josephson-like junction with linear-periodic current-phase relation. The presentation includes the ac Josephson effect, response to external rf signals and the hysteresis in the dc characteristic. The analogue has obvious value for instructional purposes and is useful where numerical analysis becomes complicated.