Mode selective properties of coaxial gyrotron resonators
- Forschungszentrum Karlsruhe-Association EURATOM-FZK (Germany). Inst. fuer Technische Physik
One of the main technological restrictions in the development of high-frequency ({approximately}170 GHz) high-power (>1 MW) CW gyrotrons for heating and current drive of magnetically confined fusion plasmas is the ohmic loading of the resonator wall, which will presently available cooling technology cannot exceed the upper limit of 2--3 kW/cm{sup 2}. Whispering gallery modes load considerably the resonator wall and high-power CW operation in such modes, within the ohmic loading limits, would require a significant increase of the resonator diameter, and thus of the mode eigenvalue for high operating frequency. In this paper, the mode-selective properties of coaxial gyrotron resonators are discussed for different cavity configurations. Expressions are derived for the ohmic loading of a coaxial conductor with longitudinal corrugations where the RF field inside the corrugations is fully taken into account, and for the diffractive quality factor in coaxial cavities with tapered inner conductor relative to that of an empty cylindrical cavity. The competing action of a kind of surface mode that appears in corrugated structures is investigated by considering its diffractive and ohmic quality factors. Additional mode competition problems that can arise in coaxial cavities with corrugated inner conductor due to second cyclotron harmonic interaction are investigated and solutions to the problem are proposed.
- OSTI ID:
- 377817
- Journal Information:
- IEEE Transactions on Plasma Science, Journal Name: IEEE Transactions on Plasma Science Journal Issue: 3 Vol. 24; ISSN ITPSBD; ISSN 0093-3813
- Country of Publication:
- United States
- Language:
- English
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