ABSTRACT
The electromagnetic characteristics of the input cavity with electron beams loaded are measured successfully in an X-band triaxial relativistic klystron amplifier (TKA) with a high frequency electrical probe. To solve the frequency response issue in the X band, a coaxial electrical probe is optimized and inserted obliquely into the input cavity at the designed angle so that the microwaves in the cavity can be sampled and extracted with the required coupling coefficient while the probe does not interfere with the solenoid coil, which is tightly integrated outside the TKA. Besides, the TKA is redesigned as a structure integrally sealed by the solenoid coil, and the secondary sealing induced by probe insertion is implemented on the flange of the solenoid coils rather than on the wall of the TKA, which is conducive to simplifying the coupling structure while maintaining the high vacuum level. The design is examined in a GW level TKA experiment, indicating that microwaves with a power of about 670 MW are generated in the input cavity at a frequency of 8.40 GHz, which is completely consistent with the injected and output microwave frequencies.
ABSTRACT
We report the first experimental demonstration of coherent combining of phase-steerable high power microwaves (HPMs) generated by X-band relativistic triaxial klystron amplifier modules under the guidance of pulsed magnetic fields. Electronically agile manipulation of the HPM phase is achieved with a mean discrepancy of 4° at the gain level of 110 dB, and the coherent combining efficiency has reached as high as 98.4%, leading to combined radiations with equivalent peak power of 4.3 GW and average pulse duration of 112 ns. The underlying phase-steering mechanism during the nonlinear beam-wave interaction process is furthermore explored by particle-in-cell simulation and theoretical analysis. This Letter paves the way for high power phase array in large scale and may stimulate new interest in research of phase-steerable high power masers.
ABSTRACT
Radial transit time oscillator (RTTO) can be relied on to generate effective coherent electromagnetic radiation in the millimeter wave domain. In this paper, the preliminary experimental research on a Ka-band RTTO is reported for the first time. In experiments, the radial electron beam emitted from the knife edge of the disk cathode is guided by the radial magnetic field. The bombardment trace on the nylon target verifies the emission and transportation uniformity of the radial e-beam. When the diode voltage is 410 kV, the beam current is 7.8 kA, and the magnetic field is 0.6 T, the RTTO can output microwaves with the power of 320 MW and the frequency of 31.35 GHz. As the diode voltage increases from 350 kV to 430 kV, the output microwave power will grow accordingly. Taking the ohmic loss into consideration, the experimental results are in agreement with the simulation ones.
ABSTRACT
Miniaturization is one of the important research directions of low frequency high power microwave sources. This paper presents a three-period coaxial slow-wave structure L-band high-power microwave source. Because the coaxial Quasi-TEM mode has no cut-off frequency, the radial size of the device can be reduced. At the same time, in order to reduce the transverse dimension, the coaxial extractor structure is introduced to realize the longitudinal mode selection and improve the conversion efficiency of the device. In simulation, the device obtains the microwave output with the central frequency of 1.53 GHz, the average power of 3.3 GW and the efficiency of 40%. By optimizing the scheme of electron beam collection, the phenomenon of pulse shortening is effectively suppressed. In the experiment, the device obtains the microwave output with the central frequency of 1.52 GHz, the average power of 3 GW, the efficiency of 33% and the pulse width of 40 ns.
