Abstract: In a substantially circular waveguide constituting a mode converter in a gyrotron tube, there is a region whose transverse inner surface shape changes to a non-true circular shape from a true circular shape in a range of 0 mm to 5 mm toward a radiation aperture from the incident side. Therefore, an undesirable cavity resonator which causes parasitic oscillation can be prevented from being formed in the vicinity of an inlet of the mode converter. Therefore, the parasitic oscillation of the mode converter can be suppressed, and a conversion efficiency of the converter can be enhanced, because of the effective length of the mode converter can be enhanced in the limited actual length.

Abstract: In a substantially circular waveguide constituting a mode converter in a gyrotron tube, there is a region whose transverse inner surface shape changes to a non-true circular shape from a true circular shape in a range of 0 mm to 5 mm toward a radiation aperture from the incident side. Therefore, an undesirable cavity resonator which causes parasitic oscillation can be prevented from being formed in the vicinity of an inlet of the mode converter. Therefore, the parasitic oscillation of the mode converter can be suppressed, and a conversion efficiency of the converter can be enhanced, because of the effective length of the mode converter can be enhanced in the limited actual length.

Abstract: An electromagnetic wave matching element makes it possible to reduce the cost of a transmission system to a great degree. An electromagnetic wave matching element is adapted to allow electromagnetic wave beams incident from an entrance to be reflected by using plural mirrors to couple these reflected electromagnetic wave beams to an external transmission system through an exit. Mirrors are used that have a shape adapted to receive the plural electromagnetic waves in a beam form and to output electromagnetic wave beams having a predetermined distribution in which the number of the output electromagnetic waves is different from the number of the received electromagnetic waves.

Abstract: An electron beam generated by an electron gun is oscillated in a cavity resonator and output as a millimeter electromagnetic wave. The output electromagnetic wave is transmitted to a cylindrical mode converter. The inner wall surface of this mode converter has a plurality of sets of ridges and grooves spirally formed at equal pitches so as to gradually change the degree of corrugation in the transmission direction of the electromagnetic wave. The mode converter separates the input electromagnetic wave from the cavity resonator into a plurality of electromagnetic waves having the same power distribution. The output electromagnetic waves from the mode converter are transformed into wave beams by mirror systems and output to the outside of a gyrotron from output windows provided in a one-to-one correspondence with these electromagnetic waves.

Abstract: There is provided a gyrotron including a quasi-optical mode converter wherein a solid dielectric layer such as silicon carbide for absorbing unnecessary millimeter waves generated by diffraction of the quasi-optical mode converter is arranged in annular shape in the periphery of the quasi-optical mode converter, and millimeter absorption fluid can be supplied to the periphery of the mode converter in a predetermined direction through vacuum barrier walls formed by a dielectric member, thereby efficiently absorbing the diffracted millimeter wave which is the cause of generating heat.