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This paper describes the results of testing an electron gun which produces a beam of rectangular cross-section, designed for use in a 120 GHz QO (quasi-optical) gyrotron. The beam is segmented into beamlets, the spacing of which is equal to half wavelength. This allows optimal interaction of the beam and the standing wave in the resonator, since it can be adjusted so that the beamlets pass through the resonator near the maximum of the RF field, and there are no electrons where the field is zero. In the ideal case the efficiency is increased by 1.4 over a uniform sheet beam. A 2-D simulation using the code EGUN indicated that the beam would be skewed because of the differential in time that the top and bottom of the beam spent in the electric field of the diode region. This problem was eliminated by slanting the emitters in the opposite direction. 3-D modelling using the code ARGUS gave similar predictions to those of EGUN coupled with adiabatic calculations.

Additional information

Authors: READ M E, Physical Sciences Inc. Alexandria (US);DUDAS A J, Physical Sciences Inc. Alexandria (US);PETILLO J, Sc. Applications Int. Corp. McLean (US);TRAN M Q, Sc. Applications Int. Corp. McLean (US)
Bibliographic Reference: Report: LRP 386/89 EN (1989)
Availability: Available from Confédération Suisse, Centre de Recherches en Physique des Plasmas, École Polytechnique Fédérale de Lausanne, 21 avenue des Bains, 1007 Lausanne (CH)
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