Gyrotron parasitic-effects studies using the time-dependent self-consistent monomode code TWANG

Basic wave-particle interaction dynamics from linear to chaotic regimes is experimentally studied on a frequency tunable gyrotron generating THz radiation in continuous mode (200 W) at 263 GHz which will be used for dynamic nuclear polarization nuclear magnetic resonance spectroscopy applications. In the studied system, the nonlinear dynamics associated to the waveparticle interaction is dominated by longitudinal mode competition of a given transverse TE m;p cavity-mode. This study covers a wide range of control parameter from gyro-traveling wave tube (gyro-TWT) to gyro-backward wave oscillator (gyro-BWO) like interactions for which extensive theoretical studies have been performed in the past on a simplified system. Besides the common route to chaos characterized by period doubling, other routes have been identified among which some are characterized by line-width frequency-broadening on the side-bands. The complex nonlinear dynamics is in good agreement with the theory and the experimental results are discussed on the basis of the prediction obtained with the nonlinear time-dependent selfconsistent codes TWANG and EURIDICE both based on a slow-time scale formulation of the self-consistent equations governing the wave-particle dynamics. V C 2012 American Institute of Physics. [http://dx

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“…These codes are TWANG 4 and EURI-DICE 5 with both codes based on a slow-time scale formulation of the electron equation of motion.…”

Section: Theoretical and Numerical Modelsmentioning

confidence: 99%

Experimental study from linear to chaotic regimes on a terahertz-frequency gyrotron oscillator

et al. 2012

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“…There are four European interaction codes, available at EGYC, based on the slow-time scale approximation and thus capable of fast simulations: EURIDICE [4], SELFT [5], COAXIAL [6], and TWANG [7]. The results of the codes are in agreement in the majority of cases that have been tested.…”

Section: Introductionmentioning

confidence: 81%

On the numerical scheme employed in gyrotron interaction simulations

Avramides

Ram

Dumbrājs

et al. 2012

EPJ Web of Conferences

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Abstract. We report on the influence of the numerical scheme employed in gyrotron interaction simulations. Results obtained with the Crank-Nicolson scheme are compared with those obtained with the Backward Time -Centred Space (BTCS) fully implicit scheme. We present realistic cases where, for discretisation parameters in the range usually used in gyrotron simulations, the results can be very different. Hence, the numerical scheme used can be responsible for obscuring the underlying physics if its convergence is not tested carefully.

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“…The new model is based on the nonlinear model of the code TWANG 14 , describing self-consistently the waveparticle interaction for a single transverse TE m,p mode. Together with its linearization it is described in details in references 6,14,15 .…”

Section: Model Descriptionmentioning

confidence: 99%

“…Together with its linearization it is described in details in references 6,14,15 . An important point to be stressed is that the amplitude and phase of the rf-field profile were considered to vary on a time-scale much longer than the electron transit-time in previous models 6,14 (in the model presented in this paper and in a new reduced 1D ParticleIn-Cell (PIC) model 15 , this assumption is relaxed). The equations describing respectively the perpendicular and parallel electron motion for each electrons are…”

Section: Model Descriptionmentioning

confidence: 99%

Novel linear analysis for a gyrotron oscillator based on a spectral approach

et al. 2016

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With the aim of getting a better physical insight in linear regimes in gyrotron, a new linear model was developed. This model is based on a spectral approach for solving the self-consistent system of equations describing the wave-particle interaction in the cavity of a gyrotron oscillator. Taking into account the walllosses self-consistently and including the main system inhomogeneities in the cavity geometry and in the magnetic field, the model is appropriate to consider real system parameters. The main advantage of the spectral approach, compared to a time-dependent approach, is the possibility to describe all the stable and unstable modes, respectively with negative and positive growth rate. This permits to reveal the existence of a new set of eigenmodes, in addition to the usual eigenmodes issued from cold-cavity modes. The proposed model can be used for studying other instabilities such as for instance backward waves potentially excited in gyrotron beam tunnels.

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Gyrotron parasitic-effects studies using the time-dependent self-consistent monomode code TWANG

Cited by 15 publications

References 6 publications

Experimental study from linear to chaotic regimes on a terahertz-frequency gyrotron oscillator

Experimental study from linear to chaotic regimes on a terahertz-frequency gyrotron oscillator

On the numerical scheme employed in gyrotron interaction simulations

Novel linear analysis for a gyrotron oscillator based on a spectral approach

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