Linear and nonlinear behaviors of gyrotron backward wave oscillators

Chen, Shih Hung; Chen, Liu

doi:10.1063/1.3688892

Cited by 11 publications

(10 citation statements)

References 31 publications

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“…Last but not least, this theoretical approach provides a direct proof of the one-on-one correspondence of chorus chirping with superradiance in free electron lasers, noted first by Zonca et al (2015b) and Chen and Zonca (2016). It is also worthwhile emphasizing that the theoretical approaches presented in this work have interesting possible applications to nonlinear phenomena in high power radiation devices such as gyrotron backwave oscillators, where they may not only be applied, but also yield in-depth understandings (Chen & Chen, 2012.…”

Section: Discussionsupporting

confidence: 63%

“…(2015b) and Chen and Zonca (2016). It is also worthwhile emphasizing that the theoretical approaches presented in this work have interesting possible applications to nonlinear phenomena in high power radiation devices such as gyrotron backwave oscillators, where they may not only be applied, but also yield in‐depth understandings (Chen & Chen, 2012, 2013).…”

Section: Discussionmentioning

confidence: 99%

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A Theoretical Framework of Chorus Wave Excitation

2022

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Chorus waves are whistler mode waves with frequency (ω) typically between one-tenth of and the electron cyclotron frequency (Ω) (see, e.g., Burtis & Helliwell, 1976;Tsurutani & Smith, 1974). These waves have been demonstrated to play important roles in energetic electron dynamics in the terrestrial magnetosphere. Chorus waves are responsible for the acceleration of a few hundred keV electrons to the MeV energy range, leading to the enhancement of MeV electron fluxes in the outer radiation belt during geomagnetically disturbed times

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Section: Discussionsupporting

confidence: 63%

Section: Discussionmentioning

confidence: 99%

A Theoretical Framework of Chorus Wave Excitation

2022

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“…Chen & Zonca, 2016). It is also worthwhile emphasizing that the theoretical approaches presented in this work have interesting possible applications to nonlinear phenomena in high power radiation devices such as gyrotron backwave oscillators, where they may not only be applied, but also yield in-depth understandings (S.-H. Chen & Chen, 2012, 2013.…”

Section: Discussionmentioning

confidence: 99%

A theoretical framework of chorus wave excitation

Zonca,

Tao,

Chen

2021

Preprint

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We propose a self-consistent theoretical framework of chorus wave excitation, which describes the evolution of the whistler fluctuation spectrum as well as the supra-thermal electron distribution function. The renormalized hot electron response is cast in the form of a Dyson-like equation, which is then manipulated to obtain evolution equations for nonlinear fluctuation growth and frequency shift. This approach allows us to analytically derive for the first time the well-known result for the chorus chirping rate originally proposed by Vomvoridis et al. (1982). Chorus chirping is shown to correspond to maximization of wave particle power exchange, where each individual wave belonging to the whistler wave packet is characterized by small nonlinear frequency shift. We also show that different interpretations of chorus chirping proposed in published literature have a consistent collocation within the present theoretical framework, which further illuminates the analogy with similar phenomena in fusion plasmas and free electron laser physics.

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“…14,15 This instability allows the gyro-BWO mode to grow and the field profile contracts to the beam entrance end. 16 As the magnetic field (B 0 ) or the beam voltage (V b ) is tuned, the electron transit angle of gyro-BWO modes varies simultaneously to satisfy the beam-wave resonance condition, thereby enabling frequency tuning. 14 On the other hand, the gyromonotron operates in a resonant structure.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic resonance in gyrotron using non-resonant RF structure

Yang,

Yao,

Chen

et al. 2024

Physics of Plasmas

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Gyromonotrons are typically believed to rely on the convective interaction between the co-propagating beam and wave, with the extended energy-exchanging process stemming from the external feedback. However, numerous studies focusing on both transverse electric (TE) mode and transverse magnetic (TM) mode gyrotrons have consistently shown that beam–wave interactions in weak-feedback systems or even in uniform tubes without any structural feedback can yield a theoretical beam efficiency of more than 30% with major forward-wave output during near-cutoff operation, which is the typical operating condition for gyromonotrons. These intriguing findings raise questions about the actual feedback mechanism of gyromonotrons. In this article, comparative studies on the linear and nonlinear behaviors of uniform-tube gyrotron are investigated. The forward and backward waves are observed to co-generate and exhibit similar characteristics of ultra-slow group velocity under near-cutoff operation. This situation allows the as-generated forward wave to modulate the fresh beam, establishing a new backward-wave-like internal feedback loop. Additionally, the quasi-degenerate nature of the bi-directional propagating waves ensures their intrinsic in-phase relationship. The consequent constructive interference enables the uniform tube to function as a high-Q resonator. These findings are found to be independent of the choices of TE or TM modes, providing valuable insights into the underlying interaction mechanism of gyrotron devices.

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Linear and nonlinear behaviors of gyrotron backward wave oscillators

Cited by 11 publications

References 31 publications

A Theoretical Framework of Chorus Wave Excitation

A Theoretical Framework of Chorus Wave Excitation

A theoretical framework of chorus wave excitation

Intrinsic resonance in gyrotron using non-resonant RF structure

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