Mode Priming in an Overmoded Gyrotron Oscillator.
Abstract
Axial mode control in a gyrotron oscillator is accomplished by injection of an external signal into the oscillator. The mechanism by which the selection technique works is that of priming, where the injected signal is required only during the early stages of oscillation growth. Like phase priming, mode control can be obtained with an external mode than any other. It is found that the external signal can select a mode when the free gyrotron operation skips between modes from pulse to pulse. Also, in certain conditions, a single stable mode can be changed to a different mode by a priming signal. Finally a case is studied where a bistable system (two simultaneous modes) is reduced to a single mode because of the external signal. Mode control is used as a diagnostic to investigate the coupling of an external electromagnetic wave to the electron beam via electron cyclotron resonance absorption. Beam-wave coupling is studied as a function of the polarization of the input drive signal. It is found that the external electromagnetic signal couples best when launched as a right-hand circularly polarized wave. The theoretical ratio (55.2) of the coupling factors for the right- and left-hand electromagnetic waves is found to be consistent with the experimentally value within the uncertainties of the measurement.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 19, 1987
- Accession Number
- ADA189151
Entities
People
- Alan H. Mccurdy
- Carter A. Armstrong
Organizations
- United States Naval Research Laboratory