Influence of wall plasma on microwave frequency and power in relativistic backward wave oscillator

Sun, Jun; Wu, Ping; Chen, Yibing; Teng, Yan; Zhang, Yuchuan; Chen, Changhua

doi:10.1063/1.4926526

Cited by 14 publications

(2 citation statements)

References 29 publications

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“…6 And plasmas in the collector influence the frequency and the output power of a BWO. 7 Moreover, plasmas in a HPM generator may cause impedance collapse and pulse shortening. 8 Besides, plasmas generated in different regions may have different impacts on the HPM generator.…”

Section: Introductionmentioning

confidence: 99%

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Plasma bombardments in the diode in Ka-band coaxial transit-time oscillator

Song

et al. 2018

AIP Advances

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Plasma is a non-ignorable factor in a high power generator. In this paper, plasma bombardments in the diode region are found in experiment on a Ka-band transit-time oscillator. Microcosmic and energy dispersive analysis has been done first on the plasma spots. Based on the Carbon contents in different areas of the diode, a physical model describing the progress of the plasma from appearance to expansion is built. Subsequently, simulations on the plasma expansion have been done with particle-in-cell code calculation. The result agrees well with the model proposed above. Finally, a special structure is adopted in the improved Ka-band coaxial TTO to suppress or even avoid the plasma Bombardment. The study is of significance to generators for long-pulsed and repetition operation.

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Section: Introductionmentioning

confidence: 99%

“…8 Besides, plasmas generated in different regions may have different impacts on the HPM generator. [5][6][7][8][9] Therefore, it is of great significance to clarify the generation of plasmas.…”

Section: Introductionmentioning

confidence: 99%

Plasma bombardments in the diode in Ka-band coaxial transit-time oscillator

Song

et al. 2018

AIP Advances

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Power combiner with high power capacity and high combination efficiency for two phase-locked relativistic backward wave oscillators

Xiao

Deng

Wang

et al. 2015

Applied Physics Letters

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To realize power combination of two phase-locked relativistic backward wave oscillators (RBWOs), a compact power combiner is designed and investigated by 3-D particle-in-cell (PIC) simulation and experiment. The power combiner consists of two TM01-TE11 serpentine mode converters with a common output. When the two incident ports are fed with TM01 modes with a relative phase of 180° and power of 2.5 GW at each port, the conversion efficiency from the incident TM01 modes to the combined TE11 mode is 95.2% at 9.3 GHz, and the maximum electric field in the combiner is 714 kV/cm. The PIC simulation shows that the output power from the common port is 4.2 GW when the power combiner is connected to the two RBWOs with input signals, both producing 2.2 GW microwave, corresponding to a combination efficiency of 95.4%. In the high power microwave test, a method is proposed to obtain the combination efficiency without breaking the vacuum, which is 94.1% when the two phase-locked RBWOs output 1.8 GW and 2.2 GW. The power capacity of multi-gigawatts has been demonstrated.

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Axial motion of collector plasma in a relativistic backward wave oscillator

et al. 2016

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In this paper, it is proposed that plasma formed at the collector may drift back to the cathode and cause pulse shortening of the relativistic backward wave oscillator. Theoretical analysis shows that the axial drift velocity of plasma ions can be up to 5 mm/ns due to the presence of space charge potential provided by an intense relativistic electron beam. Particle-in-cell simulations indicate that the plasma electrons are initially trapped around the collector surface. With the accumulation of the plasma ions, a large electrostatic field forms and drives the plasma electrons to overcome the space charge potential and enter the beam-wave interaction region along the magnetic field lines. As a result, the beam current modulation is disturbed and the output microwave power falls rapidly. The plasma ions move in the beam-wave interaction region with an average axial velocity of 5–8 mm/ns. After the plasma ions reach the diode region, the emitted current at the cathode rises due to the charge neutralizations by the ions. The impedance collapse leads to further decrease of the microwave power. In experiments, when the diode voltage and beam current were 850 kV and 9.2 kA, and the collector radius was 2.15 cm, the output microwave power was 2.4 GW with a pulse width of less than 20 ns. The ion drift velocity was estimated to be about 5 mm/ns. After an improved collector with 3.35 cm radius was adopted, the pulse width was prolonged to more than 30 ns.

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Influence of wall plasma on microwave frequency and power in relativistic backward wave oscillator

Cited by 14 publications

References 29 publications

Plasma bombardments in the diode in Ka-band coaxial transit-time oscillator

Plasma bombardments in the diode in Ka-band coaxial transit-time oscillator

Power combiner with high power capacity and high combination efficiency for two phase-locked relativistic backward wave oscillators

Axial motion of collector plasma in a relativistic backward wave oscillator

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