High Gain Relativistic Klystron Amplifier Self-oscillating Mechanism And Suppression Technique

As the technology of structure process and power capacity of high-power microwave devices are restricted, the output power of a single device is quite close to its limitation. To achieve higher output power at present, a feasible way is the combination of several high-power microwave devices. Because intense relativistic klystron amplifier (1RKA) has characteristics of high gain, high power, locking of phase and frequency, it was used for power combination. However self-oscillation will seriously affect the device’s operating characteristics, espicially for the high gain cases. And the high gain devices need very lower rf input power to drive, so the technologhy pressure can be significantly decreased compared with the low gain cases. In order to accomplish a high gain (more than50dB) relativistics klystron ampilfier, an S-band1RKA with four cavities is chose to study self-oscillation mechanism and suppression technology through theory analyze, particle simulation and experimental research.The mechanism of monotron oscillation and couple between cavities are investigated for the suppression of the non-working modes’excitation as follows.(1) The physics mechanism of monotron oscillation is analyzed to give the transit angle’s range for each caviy in the sturture;(2) Another kind of self-oscillation is also analyzed base on the couple between cavities, and the relationships between starting current of oscillation and structure parameters are given. So some methods of suppression high mode oscillation to increase the starting current of oscillation (such as adjusting length of drift tube between idle cavities and decreasing Q value of idle cavities) are proposed.(3)the validity of supressing method are not only proved in PIC simulation, but also under the condition of2.3kW input microwave power, output microwave with power of3GW, efficiency of24%, gain of61dB is obtainedIn intense relativist]c klystron amplifier, the raltion between the returning electrons and the design of output cavity, the parameter of beam and inject microwave is given. Four aspects are studied:(1) the radial force expressions of returning electrons is deduced, which well explained the phenomena of returning electronic easily diffusing and intercepted by drift tube;(2) the generating mechanism of returning electrons is studied, the study shows that the electronic reflux is closely related to voltage of output cavity gap, electronic initial phase and electronic initial kinetic energy;(3)the condition of current intension and phase of returning electron which excite oscillation in the upstream cavities is ananlyzed;(4)through simulationt to study how parameters of structure, input microwave power and electron beam affect the electronic returning, and then propose some restraining methods, these retraining measures is validated in simulation,the study found that output microwave with higher power,higher gain, phase and frequency locking,and higher efficiency can not be attained untill comprehensive suppressing measures are adopted.According to the self-oscillation supressing method,an S-band3GW high gain IRKA is designed through PIC simulation,an output microwave with power of3GW,efficiency of24%,gain of61dB is obtained.(?) the (?) time,an experiment research of(?)(?)(?)with the input microwave powe the of10kW level,the high power microweive with bandwidth of103ns,effiency of26.5%,gain of52dBand GW level output power is obtained.