Gain and bandwidth of the gyro-TWT and CARM amplifiers

Chu, K. R.; Lin, A. T.

doi:10.1109/27.3798

Cited by 191 publications

(60 citation statements)

References 33 publications

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“…As the gyrotron works near the cut-off frequency region, and a large orbit gyrotron requires s = m, the operating frequency (390 GHz) and harmonic number (s = 7) as well as the azimuthal index of the waveguide mode (m = 7) were chosen prior to the cavity size. The interaction of the waveguide mode and axisencircling electron beam cyclotron mode can be described by the equation below [21,22]:…”

Section: Gyrotron Designmentioning

confidence: 99%

Design and simulation of a ∼390 GHz seventh harmonic gyrotron using a large orbit electron beam

Li¹,

He²,

Cross³

et al. 2010

J. Phys. D: Appl. Phys.

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Abstract. A~390 GHz harmonic gyrotron based on a cusp electron gun has been designed and numerically modelled. The gyrotron operates at the 7 th harmonic of the electron cyclotron frequency with the beam interacting with a TE 71 waveguide mode. Theoretical as well as numerical simulation results using the 3D Particle-In-Cell (PIC) code MAGIC are presented. The cusp gun generated an axis-encircling, annular shaped electron beam of energy 40 keV, current 1.5 A with a velocity ratio of 3. Smooth cylindrical waveguides have been studied as the interaction cavities and their cavity Q optimized for 390 GHz operation. In the simulations 600 W of output power at the design frequency has been demonstrated. [5,6]. The gyrotron is well known as a coherent millimeter wave source capable of high power and high frequency output which is extendable to the Terahertz (THz) frequency region. Recently a gyrotron achieved kilowatts of output power operated at the fundamental electron cyclotron frequency of 1 THz [7] by using a pulsed solenoid. However, continuous wave (CW) operation at such a frequency is a formidable task because of the large magnetic field (~40 T) that is required. As the output frequency increases, both larger magnetic fields and reduced interaction region size are needed when operating at the fundamental cyclotron frequency. An alternative approach to generate CW high frequency radiation is to work at higher cyclotron harmonics [8,9,10,11] which allow the use of larger cavity sizes and smaller magnetic fields by a factor of s, where s is the harmonic number. A CW high harmonic gyrotron operating at a frequency of~390 GHz at relatively lower B-field was designed and is presented in this paper. In this gyrotron cyclotron resonance takes place between the seventh harmonic of the electron cyclotron frequency (s = 7) and the TE 71 waveguide mode. A large orbit electron beam from a cusp gun is used to reduce the possibility of parasitic interactions. The small-signal theory of the beam-wave interaction was used to calculate the growth rate and the starting current. A smooth-bore cavity was designed with a suitable Q value by optimizing the angle of the output taper and the length of the cavity so that the starting current requirement is met. Finally, the beam-wave interaction of the gyrotron was simulated using the 3D Particle-In-Cell (PIC) code MAGIC and the results are presented. Keywords: Harmonic gyrotron, terahertz, large orbit electron beam

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Section: Gyrotron Designmentioning

confidence: 99%

Design and simulation of a ∼390 GHz seventh harmonic gyrotron using a large orbit electron beam

Li¹,

He²,

Cross³

et al. 2010

J. Phys. D: Appl. Phys.

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“…Although the derivation of the dispersion relation by Chu et al [2] for TE modes is free from any of these drawbacks, their treatment is too sketchy leaving out many details of analysis. However, a complete derivation with all details filled in has been provided by Chu et al in a subsequent paper [4]. Fliflet [3], on the other hand, gives a detailed derivation of the linear dispersion relation together with a description of the single-particle quasilinear theory for both TE and TM modes.…”

Section: Introductionmentioning

confidence: 99%

“…However, he contradicts this hypothesis in a subsequent step by assuming a 'delta-function' dependence for f o on r o . Chu and Lin [4], on the contrary, do no drop the ∂ f o /∂r o terms at any stage of their derivation of the dispersion relation except that they too assume a 'delta-function' dependence for a differentiable function of r o ! It is shown in Section 2 that the axially symmetric equilibrium distribution function corresponding to an applied axially directed uniform magnetic field will be independent of r o .…”

Section: Introductionmentioning

confidence: 99%

“…The resulting biquadratic algebraic equation may be solved for the (complex) propagation phase constant as a function of the operating frequency. The works of Edgcombe [1], Chu et al [2], Fliflet [3] and Chu and Lin [4] may be cited as being specifically directed towards a derivation of the linear dispersion relation for circular cylindrical wave-guide modes. Edgecombe [1] assumes without adequate justification that the r.f.…”

Section: Introductionmentioning

confidence: 99%

“…The mechanism of small-signal amplification in gyro-TWTs and cyclotron resonance masers (CRMs) was actively studied by many researchers in the 1980s [1][2][3][4] culminating in the derivation of the dispersion relation in the form of an infinite series. The celebrated (Doppler-shifted) cyclotron resonance condition ω − v z β mn (ω) − sΩ e /γ = 0 (1) was identified as a sufficient requirement for small-signal amplification.…”

Section: Introductionmentioning

confidence: 99%

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On Small-Signal Amplification in a Gyro-TWT

Kalyanasundaram¹,

Saini²

2011

PIER C

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Abstract-The corrected dispersion relation governing the linear interaction of a TE mode in a circular cylindrical wave guide with an annular beam of gyrating electrons in a gyro-TWT configuration is derived. The derivation of the correct dispersion relation no longer involves any integration with respect to the radial coordinate r o of the electron guiding center as the relevant equilibrium distribution function turns out to be independent of r o . When the cyclotron resonance condition is satisfied by the TE mode for a positive s-number, the small-signal theory is shown to predict an initial exponential growth of the mode with interaction length over a small but finite band of frequencies around the design frequency.

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