A Ku-band coaxial relativistic transit-time oscillator with low guiding magnetic field

Abstract

A novel coaxial relativistic transit-time oscillator with low guiding magnetic field is proposed and investigated to generate high power microwave at Ku-band. With the coaxial structure and a quasi body wave adopted as the operating mode, the device has a larger space-charge limiting current, higher power handling capacity, and lower guiding magnetic field. Moreover, for further improving the output power, a coaxial TM 02 mode resonant reflector is well designed. Main structure parameters of the device are optimized by particle in cell simulations. A typical simulation result is that, with a 358 keV, 7.25 kA beam guided by a magnetic field of about 0.7 T, an 810 MW microwave pulse at 14.25 GHz is generated, yielding a conversion efficiency of about 31%. The primary experiments are also carried out. At a low guiding magnetic field of 0.7 T, a microwave pulse with power of 400 MW, pulse duration of 30 ns, frequency of 14.3 GHz close to the simulation one, and efficiency of 15.4% is generated.

A Ka-band TM02 mode relativistic backward wave oscillator with cascaded resonators

“…TM 02 mode provides higher power handling capability than TM 01 mode does. 12 And for the same output frequency, the structure sizes of RBWO operating in TM 02 mode are considerably larger than that operating in TM 01 mode. This facilitates the fabrication and assembly of the Ka-band generator.…”

“…12 The microwave leaking into the diode region is likely to disturb the explosive emission of the annular cathode and the transmission of the electron beam. In order to eliminate the leakage, the front cascaded resonators consisting of three resonant reflectors instead of the traditional resonant reflector are applied at the beginning end of the overmoded SWS as shown in Fig.…”

“…This disturbs the explosive emission and the transmission of the electron beam. 12 For the foresaid problems, this paper proposes a Ka-band RBWO complemented by cascaded resonators as shown in Fig. 1.…”

“…The proposed RBWO operates in TM 02 mode but the microwave pulse radiates in the pure TM 01 mode. TM 02 mode is considered as the volumetric wave remarked by higher power handling capability than the surface wave, such as FIG 12 In terms of the power handling capability and the conversion efficiency, the ripples of the overmoded SWS are improved into the structure composed of semicircle on top of the rectangle. The cascaded resonators at both ends of SWS can significantly enhance the conversion efficiency, and the front cascaded resonators efficiently prevent the power generated in SWS from leaking into the diode region.…”

Suppression of the asymmetric competition mode in the relativistic Ku-band coaxial transit-time oscillator

“…[10][11][12] In our previous research, by combining the advantages of the traditional TTO and the coaxial structure, we proposed a Ku-band coaxial TTO, which could output 400 MW microwave at 14.3 GHz under the diode voltage 360 kV, current 7.2 kA, and guiding magnetic field 0.7 T in the primary experiments. 13 However, in our recent work, with the increase of the input electric power, the experimental microwave power of the device is limited by the mode competition. For obtaining higher Ku-band HPM, the investigations on the methods for suppression of the competition mode in the device have been carried out.…”