Performance of Weakly Relativistic Oversized Backward Wave Oscillators

Yambe

et al. 2016

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A W-band (75-110 GHz) oversized surface wave oscillator driven by weakly relativistic electron beams with energy in the range of 10-80 keV is studied. Rectangular corrugations are used as slow-wave structures (SWS) having surface waves with an upper cutoff frequency of approximately 100 GHz (W-band). Uniformly distributed annular electron beams are generated by a disk-type cold cathode and then are injected into the W-band oscillator. A longer SWS length causes the oscillator to function in both backward wave oscillator (BWO) and travelling wave tube (TWT) operations, and no meaningful oscillation occurs at the π-point or the Bragg condition. When the SWS length is short enough, oscillation occurs in all regions: BWO, π-point and TWT. The operations of the oscillator are strongly affected by the structure length. The maximum radiation power is estimated to be approximately 20 kW with the figure of merit of about 2 × 10 2 MW.GHz 2 .

Section: Introductionmentioning

confidence: 99%

Experimental Study on W-Band (75 - 110 GHz) Oversized Surface Wave Oscillator Driven by Weakly Relativistic Electron Beams

San

Yambe

et al. 2016

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“…One is the rectangularly corrugated waveguide shown in Fig. 1, which has commonly been used in oversized BWOs [2][3][4][8][9][10]. The other is the rectangularly corrugated cylinder shown in Fig.…”

Section: G-band Swsmentioning

confidence: 99%

“…By using uniformly distributed annular electron beams, oversized BWOs operating at less than 100 kV have been studied in the K-and Q-bands [8][9][10]. An annular beam of the order of 100 A completely covers the corrugated surface.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on G-Band Oversized Backward Wave Oscillator Driven by Weakly Relativistic Electron Beam

Magori

Iwasaki

et al. 2014

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We studied a G-band oversized backward wave oscillator (BWO) driven by a weakly relativistic electron beam of less than 100 kV. Rectangular corrugations are used as slow-wave structures having surface waves with upper cutoff frequencies above 150 GHz (G-band). We examine how dispersion characteristics of surface waves are affected by accuracy in machining the corrugation amplitude, width, and period length. Of these, accuracy in the amplitude has the largest effect. Uniformly distributed annular electron beams are generated by a disk-type cold cathode and injected into the G-band BWO. G-band BWO operations in 137-173 GHz and above 173 GHz are achieved by changing the corrugation amplitude. The radiation patterns are fairly broad, and the estimated radiation power is at kW level.

“…For oversized BWOs using a hollow SWS, it has been shown theoretically and experimentally that a critical beam energy exists (the so-called starting energy) at which meaningful radiations begins to oscillate [1,7]. In Fig.…”

Section: Coaxial Oversized Bwo Experimentsmentioning

confidence: 99%

“…In slowwave devices, slow-wave structure (SWS) is used to reduce the phase velocity of electromagnetic waves to the beam velocity. To increase the operating frequency and powerhandling capability, oversized devices have been used successfully [1,2]. The term "oversized" means that the diameter D of the SWS is larger than the free-space wavelength λ of the output electromagnetic waves by at least several times.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Oversized Backward Wave Oscillator with Coaxial Slow-Wave Structure

Yoshimura

Bansho

et al. 2010

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Studies of coaxial oversized backward wave oscillators (BWOs) are reported. The beam voltage is weakly relativistic (less than 100 kV). The slow-wave structure consists of a periodically corrugated oversized waveguide and periodically corrugated inner conductor, whose target operating frequency due to Cherenkov interaction is in the K-band. A starting energy exists for the coaxial oversized BWO as it does for a hollow oversized BWO. The coaxial slow-wave structure has two surface wave modes caused by the inner and outer corrugations. Operation based on these surface modes can be controlled by the beam diameter. The phase difference between the inner and outer corrugations has little effect on operation of the oversized BWO.