Startup Scenarios in High-Power Gyrotrons

Nusinovich, Gregory S.; Sinitsyn, O. V.; Velikovich, L.; Yeddulla, M.; Antonsen, Thomas M.; Vlasov, Alexander N.; Cauffman, S.; Felch, K.

doi:10.1109/tps.2004.828854

Cited by 63 publications

(12 citation statements)

References 35 publications

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“…In this section, we analyze the mode competition and startup scenarios of the TE 22,6 and the TE 19,7 sequence of the mode startup is vital in deciding the eventual dominant mode. 17,18 By studying the relative values of start current of the two modes during the evolution of the voltage, current, and alpha, we can predict the eventual dominant mode. The generalized equation for the start current in an overmoded gyrotron is…”

Section: Startup Scenario Analysismentioning

confidence: 99%

Experimental results for a 1.5MW, 110GHz gyrotron oscillator with reduced mode competition

et al. 2006

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A new result from a 110GHz gyrotron at MIT is reported with an output power of 1.67MW and an efficiency of 42% when operated at 97kV and 41A for 3μs pulses in the TE22,6 mode. These results are a major improvement over results obtained with an earlier cavity design, which produced 1.43MW of power at 37% efficiency. These new results were obtained using a cavity with a reduced output taper angle and a lower ohmic loss when compared with the earlier cavity. The improved operation is shown experimentally to be the result of reduced mode competition from the nearby TE19,7 mode. The reduced mode competition agrees well with an analysis of the startup scenario based on starting current simulations. The present results should prove useful in planning long pulse and CW versions of the 110GHz gyrotron.

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Section: Startup Scenario Analysismentioning

confidence: 99%

Experimental results for a 1.5MW, 110GHz gyrotron oscillator with reduced mode competition

et al. 2006

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show abstract

“…Up to now there is no general computationally efficient solution for arbitrary number of modes with arbitrary indices and arbitrary frequencies. The recent development of the models is based on the most common patterns of mode competition in gyrotrons [4,5], namely triplet (or multiplet) of modes capable of parametric cross-excitation and doublet of modes with different azimuthal indices. The developed models allow for combination of triplets and doublets of modes to resolve main sequence of modes among large number of modes capable of self-excitation and competition.…”

Section: Magy Models For Mode Interaction In Gyrotronsmentioning

confidence: 99%

Numerical models of mode interaction in gyrotrons: Capabilities and limitations

Vlasov¹,

Chernyavskiy²,

Antonsen

et al. 2008

2008 IEEE International Vacuum Electronics Conference

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Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. Operation at high order modes increases possibility of excitation of several modes capable of efficient interaction with an electron beam during start up process. Starting current of several modes is below the operating current for all operating values of beam energy, see Fig.1. Presence of several modes leads to complicated processes of mode competition during start-up. Gyrotron design requires accurate simulations of start-up scenario to be able to control gyrotron operation at optimal efficiency at desired mode. Computationally efficient code, such as MAGY [2,3], is suitable for mode competition modeling during the long voltage rise time with respect to period of operating frequency.This presentation devoted to recent development of MAGY model that allows effective simulations of start-up scenario in gyrotrons with dense mode spectrum, such as the FZK 170 GHz gyrotron. The development of new models is motivated by the needs of accurate modeling of mode competition involves six or eight modes. This includes modes both at fundamental and cyclotron harmonics. MAGY Models for Mode Interaction in GyrotronsAccurate simulations of mode competition process in gyrotrons with dense spectrum is challenging task even for the efficient code MAGY. Up to now there is no general computationally efficient solution for arbitrary number of modes with arbitrary indices and arbitrary frequencies. The recent development of the models is based on the most common patterns of mode competition in gyrotrons [4,5], namely triplet (or multiplet) of modes capable of parametric cross-excitation and doublet of modes with different azimuthal indices. The developed models allow for combination of triplets and doublets of modes to resolve main sequence of modes among large number of modes capable of self-excitation and competition.Simulations of mode interaction processes involving large number of modes require models with large number of particles included in simulations. If number of particles is N for the single mode model, then it should be N 2 for the two of three modes and N 3 for six or eight modes to provide the same level of accuracy of simulations. A typical run time for MAGY simulation at PC type computers (Pentium 4, 3.4 GH...

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“…Mode competition during gyrotron startup is also an important problem because the cyclotron resonance condition can be fulfilled for a large number of modes during the voltage increase from zero to its nominal value. Several studies [5,6] have shown that the excitation of one or two parasitic modes is practically unavoidable. Therefore, optimum design of the resonant cavity for gyrotron oscillators requires analysis of the startup scenario.…”

Section: Introductionmentioning

confidence: 99%

Code development for the calculations of time-dependent multimode oscillations in the cavity of the future high-power gyrotrons

Numakura¹,

Imai²,

Kariya³

et al. 2016

AIP Conference Proceedings

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Investigations and advanced concepts on gyrotron interaction modeling and simulations Physics of Plasmas 22, 123114 (2015) Abstract. A computational code for the electromagnetic field in the cavity of high-power gyrotrons is developed. The gyrotron mechanism is described by a self-consistent set of equations taking into account the dependence of the axial structure of microwave oscillations on the relativistic electron beam in the cavity. The parameters of the electron beam are calculated using the EGUN electron trajectory code, and the effects of the space charge and the velocity spread of the electron beams are considered. The computational code includes a time-dependent description of the electromagnetic field and a self-consistent analysis of the electron beams. The equations are solved using a second-order predictor-corrector scheme. The calculations of the present study are carried out for a 1-MW gyrotron developed for the GAMMA10/PDX tandem mirror (80 kV, operating mode: TE94 mode, 35.45 GHz). The calculations reveal that, using a triode-type electron gun, stable excitation of the desired mode can be realized in standard startup scenarios.

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Startup Scenarios in High-Power Gyrotrons

Cited by 63 publications

References 35 publications

Experimental results for a 1.5MW, 110GHz gyrotron oscillator with reduced mode competition

Experimental results for a 1.5MW, 110GHz gyrotron oscillator with reduced mode competition

Numerical models of mode interaction in gyrotrons: Capabilities and limitations

Code development for the calculations of time-dependent multimode oscillations in the cavity of the future high-power gyrotrons

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