Scaling studies and time-resolved microwave measurements on a relativistic backward-wave oscillator

Author

Swegle, J.A. ; Anderson, R.A. ; Camacho, J.F. ; Poole, B.R. ; Rhodes, M.A. ; Rosenbury, E.T. ; Shaeffer, D.L.

Author_Institution

Lawrence Livermore Nat. Lab., California Univ., Livermore, CA, USA

Volume

21

Issue

6

fYear

1993

fDate

12/1/1993 12:00:00 AM

Firstpage

714

Lastpage

724

Abstract

A relativistic backward-wave oscillator (BWO) operating at a frequency near 8 GHz has been built. The parameters of the 60-ns electron beam driving this microwave source are varied over the ranges 0.8-1.5 MV and 2-10 kA. Several different annular cathodes for launching the electron beam are tried, varying the outer radius and shape. The axial magnetic field guiding the beam through the BWO is varied between 0.6 and 3 T. The power transfer downstream to an output waveguide is investigated as a function of the shape of the transition from the BWO to the waveguide. The scaling of the output power and frequency with these variations is discussed. Time-resolved measurements of 2-ns-long segments of the microwave output are shown. In observations of the microwave signal, it is found that the frequency shifts as the output power envelope passes through a sharp dip. It is proposed that this shift corresponds to a change in the longitudinal operating mode of the BWO

Keywords

backward wave tubes; cathodes; microwave generation; microwave measurement; relativistic electron beam tubes; 0.6 to 3 T; 0.8 to 1.5 MV; 2 to 10 kA; 60 ns; 8 GHz; annular cathodes; axial magnetic field; frequency shifts; longitudinal operating mode; microwave output; microwave source; output power envelope; output waveguide; power transfer; relativistic backward-wave oscillator; scaling; time-resolved measurements; time-resolved microwave measurements; Electromagnetic waveguides; Electron beams; Frequency; High power microwave generation; Magnetic fields; Microwave measurements; Microwave oscillators; Power generation; Shape; Waveguide transitions;

fLanguage

English

Journal_Title

Plasma Science, IEEE Transactions on

Publisher

ieee

ISSN

0093-3813

Type

jour

DOI

10.1109/27.256791

Filename

256791