Measurement of the parallel velocity distribution function of the electron beam in a quasi‐optical gyrotron by Electron Cyclotron Emission

The parallel velocity distribution function of the weakly relativistic electron beam of a quasi‐optical gyrotron has been determined by measuring the Doppler‐shifted Electron Cyclotron Emission (ECE) at an angle θ=15° with respect to the external magnetic dc‐field. Due to the Doppler shift, the freq...

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Bibliographic Details
Published in:Physics of plasmas 1996-09, Vol.3 (9), p.3501-3506
Main Authors: Soumagne, G., Alberti, S., Hogge, J. P., Pedrozzi, M., Siegrist, M. R., Tran, M. Q., Tran, T. M.
Format: Article
Language:English
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Summary:The parallel velocity distribution function of the weakly relativistic electron beam of a quasi‐optical gyrotron has been determined by measuring the Doppler‐shifted Electron Cyclotron Emission (ECE) at an angle θ=15° with respect to the external magnetic dc‐field. Due to the Doppler shift, the frequency of the spontaneous cyclotron emission at the fundamental (ν0=100 GHz) is upshifted to 140 GHz. A broadening of the spectrum up to 10 GHz [full width at half maximium (FWHM)] was measured. The measured mean frequency agrees well with the theoretical predictions, but the observed line‐width, and hence the parallel velocity distribution function, is 2–3 times larger than expected. Considerations on ECE‐measurements of the electron beam energy spread, performed at larger angles θ, are also discussed.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.871500