Broadband Plasma Relativistic Microwave Source with a Short Pulse Duration
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IED PHYSICS
Broadband Plasma Relativistic Microwave Source with a Short Pulse Duration D. K. Ulyanova, *, I. L. Bogdankevicha, S. E. Ernylevaa, and S. E. Andreeva a Prokhorov
General Physics Institute of the Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received October 10, 2018
Abstract—This study continues a series of works on creating a broadband plasma microwave sources on the basis of a smooth waveguide. Various methods for creating microwave sources and various methods for feedback uncoupling are considered with the purpose of generating continuous-spectrum microwave radiation. It is shown by numerical simulations that the plasma relativistic oscillator can be transformed into a noise amplifier by changing the parameters of the system. The numerical simulations allow one to determine the operating parameters of the experimental devices that are planned to be created and investigated in the future. It is shown that, when the time of the wave passage along the microwave oscillator exceeds the duration of the relativistic electron beam (REB) pulse, the microwave spectrum is continuous. However, if the wave passage time is much shorter than the REB pulse duration, then a line microwave spectrum will be observed at frequencies at which the oscillator length is a multiple of the half-wave, because microwave generation occurs on the longitudinal types of plasma oscillator modes. The tuning of the average microwave frequency from 3 to 9 GHz is achieved at a power of about 40 MW. DOI: 10.1134/S1063780X19080117
1. INTRODUCTION Plasma relativistic microwave oscillators and amplifiers (PRMOs and PRMAs) belong to a specific class of microwave devices. These are plasma masers based on the interaction of a high-current annular relativistic electron beam (REB) with a tubular plasma. A distinctive feature of plasma masers is the possibility of tuning the average microwave frequency in a wide range by varying the plasma density. For example, in [1], seven-fold tuning of the microwave frequency from pulse to pulse was achieved at a microwave power of 50 MW and microwave pulse duration of 20 ns. Similar results were later obtained in other frequency ranges in both the amplification and generation modes. In [2], the frequency tuning was demonstrated in the pulse-periodic mode at a repetition rate of 50 Hz. In each pulse of the microwave packet, the radiation frequency was determined by the plasma density prepared before the REB pulse (the plasma density in each pulse could be specified in accordance with a prescribed time dependence). The fourfold microwave frequency tuning was achieved within one packet of microwave pulses. Of particular interest are studies of a PRMO with an inverse geometry, which was previously used in several works [3–5]. Such a design is convenient for microwave oscillators operating in the pulse-periodic mode, because it makes much easier to cool the collector. Another advantage of this geometry is the pos-
sibility of using high REB currents [3, 4], whereas the classica
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