Abstract
The radio-frequency breakdown due to ultrahigh electric field strength essentially limits power handling capability of an individual high power microwave (HPM) generator, and this issue becomes more challenging for high frequency bands. Coherent power combining therefore provides an alternative approach to achieve an equivalent peak power of the order of ∼100 GW, which consequently provides opportunities to explore microwave related physics at extremes. The triaxial klystron amplifier (TKA) is a promising candidate for coherent power combing in high frequency bands owing to its intrinsic merit of high power capacity, nevertheless phase-locked long pulse radiation from TKA has not yet been obtained experimentally as the coaxial structure of TKA can easily lead to self-excitation of parasitic modes. In this paper, we present investigations into an X-band TKA capable of producing 1.1 GW HPMs with pulse duration of about 103 ns at the frequency of 9.375 GHz in experiment. Furthermore, the shot-to-shot fluctuation standard deviation of the phase shifts between the input and output microwaves is demonstrated to be less than 10°. The reported achievements open up prospects for accomplishing coherent power combining of X-band HPMs in the near future, and might also excite new development interests concerning high frequency TKAs.
Highlights
The radio-frequency breakdown due to ultrahigh electric field strength essentially limits power handling capability of an individual high power microwave (HPM) generator, and this issue becomes more challenging for high frequency bands
Notwithstanding the inspiring achievements, the output microwave power of a single HPM generator can hardly be further enhanced owing to an intrinsic physical limit: surface plasma formation due to breakdown on metal surface induced by ultrahigh radio-frequency electric field strength, usually termed as radio-frequency breakdown[3,4,5,6,7]
Pulsed accelerator, which was capable of providing an electrical power up to 5 GW with a full width at half maximum (FWHM) pulse duration of about 150 ns
Summary
The radio-frequency breakdown due to ultrahigh electric field strength essentially limits power handling capability of an individual high power microwave (HPM) generator, and this issue becomes more challenging for high frequency bands. The triaxial klystron amplifier (TKA) is a promising candidate for coherent power combing in high frequency bands owing to its intrinsic merit of high power capacity, phase-locked long pulse radiation from TKA has not yet been obtained experimentally as the coaxial structure of TKA can lead to self-excitation of parasitic modes. The relativistic klystron amplifier (RKA)[11,12,13,14], owing to its specific capability to lock the output HPM frequency and phase by input signal, is naturally suitable for coherent power combing. We present investigations into an improved X-band TKA and the associated experimental results of HPM radiations with peak power more than 1 GW, pulse duration in excess of 100 ns, and most remarkably with shot-to-shot phase shift fluctuation (standard deviation) less than 10°. We discuss the issues that should be addressed to achieve a high efficient coherent power combining in experiment
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