Simulation of rapid startup in microwave magnetrons with azimuthally-varying axial magnetic fields

Jones, M. C.; Neculaes, V.B.; White, W.; Lau, Y. Y.; Gilgenbach, R. M.; Luginsland, J.W.; Pengvanich, P.; Jordan, Nicholas M.; Hidaka, Yoshiki; Bosman, H.

doi:10.1109/ivelec.2004.1316255

Cited by 5 publications

(15 citation statements)

References 2 publications

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“…Noise reduction for 2.45-GHz microwave oven magnetrons is an important issue, as there exists an increasing concern about signal interference for cordless phones and wireless communications systems which also operate in this unlicensed frequency band [3], [4]. Not only the low noise behavior was observed, but also the startup was found to be substantially hastened when the number of the perturbing magnets equals the number of electron spokes in the operating mode of the magnetron (usually the pi-mode, in which the radio frequency (RF) electric field differs by in neighboring cavities [2], [5]). We call this technique "magnetic priming" and for an -cavity magnetron operating in the pi-mode it consists of imposition of /2 azimuthal magnetic field perturbations.…”

Section: Rapid Kinematic Bunching and Parametric Instability In A Cromentioning

confidence: 99%

“…They have few counterparts in the much better understood electron beam-driven devices such as the klystron, traveling wave tube, gyrotron, and free electron laser [18]. Thus, the additional embodiments associated with the azimuthal perturbations in the axial magnetic field in the low-noise magnetron [1], [2], [5], [6] prompted an analysis beginning with single particle orbits. Here, we report the findings of such a study.…”

Section: Rapid Kinematic Bunching and Parametric Instability In A Cromentioning

confidence: 99%

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Rapid kinematic bunching and parametric instability in a crossed-field gap with a periodic magnetic field

Neculaes

Pengvanich

Hidaka

et al. 2005

IEEE Trans. Plasma Sci.

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Single particle orbit considerations show that the cycloidal orbits of electrons in a gap with crossed electric and magnetic fields lead to rapid spoke formation if the external magnetic field has a periodic variation. This spoke formation is primarily a result of kinematic bunching, which is independent of the radio frequency electric field and of the space charge field. A parametric instability in the orbits, which brings a fraction of the electrons from the cathode to the anode region, is discovered. These results are examined in light of the recent rapid startup, low noise magnetron experiments and simulations that employed periodic, azimuthal perturbations in the axial magnetic field.

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Section: Rapid Kinematic Bunching and Parametric Instability In A Cromentioning

confidence: 99%

Section: Rapid Kinematic Bunching and Parametric Instability In A Cromentioning

confidence: 99%

Rapid kinematic bunching and parametric instability in a crossed-field gap with a periodic magnetic field

Neculaes

Pengvanich

Hidaka

et al. 2005

IEEE Trans. Plasma Sci.

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“…[9,11 ] By first studying the nonreiativistic, thermionic magnetron, we discover a parametric instability in the electron orbits which provide instantaneous creation of the electron spokes, even before the rf mode is excited. [12] This is a very important discovery, because even in the MAGIC simulations, startup is a major issue.…”

Section: Magnetic Primingmentioning

confidence: 99%

Relativistic Magnetron Priming Experiments and Theory

Gilgenbach¹,

Lau²

2005

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The publit reporting burden for this collection of information is estimated to average 1 hour per response, including ' gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments information, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Conthat notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a ». control number. PLEASE DO NOT RETURN YOUR FORWI TO THE ABOVE ORGANIZATION.AFRL-SR-AR-TR-05- PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)University of Michigan Ann Arbor, MI 48109 PERFORMING ORGANIZATION REPORT NUMBER SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Air Force Microwave/ RF priming experiments have been performed on the UM relativistic magnetron. The high power RF priming source (40 kV, non-relativistic magnetron) was obtained on-loan from the Air Force Research Lab. Microwave power output from the AFRL priming magnetron was input into one arm of the three-waveguide exfraction system on the relativistic magnetron. The UM/ Titan A6 relativistic magnetron was driven by MELBA-C; the ceramic insulator yields 10-8 Torr scale vacuum for quasi-hard-tube conditions. Microwave priming experiments showed mode-beating effects at power levels and frequency detuning consistent with Adier's equation. Effects of microwave priming on start-oscillation time and microwave pulselength were also characterized. Major breakthroughs in this research were the discovery and demonstration of two new magnetron priming techniques: magnetic priming and cathode priming. Magnetic priming was patented by UM (US patent No. 6,872,929

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“…The basic physical phenomena which are govern relativistic magnetron operation are well described in textbooks and reviews [1][2][3] and several methods for improving it operation, i.e., fast turn on of MW generation [4], elimination of mode competition [5], improved extraction of the MW [6], and improvements in electron emission [7,8], have been suggested. However, the influence of the cathode plasma on the beginning, duration and other parameters of the MW generation is not yet completely understood.…”

Section: Introductionmentioning

confidence: 99%

“…[8,9] These cathodes can be considered as a passive cathodes because the source of electrons is explosive emission plasma which is generated during the application of the accelerating pulse [10,11,12]. The parameters of this explosive plasma (time delay in the plasma generation, plasma density and temperature, plasma uniformity and expansion velocity) depend on the parameters of the accelerating pulse, namely, on its amplitude and rise time.…”

Section: Introductionmentioning

confidence: 99%

Relativistic magnetron operation with explosive emission and ferroelectric plasma source cathodes

Hadas

Sayapin

Kweller

et al. 2009

2009 IEEE International Conference on Plasma Science - Abstracts

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In this report we present results of comparison of experimental research of the relativistic magnetron operation with commonly used explosive emission plasma cathode and novel ferroelectric plasma source (FPS) cathode. The experiments were carried with relativistic Sband magnetron powered by Linear Induction Accelerator (LIA) (~350kV, 4kA, 200ns). Using time-and spaceresolved electrical, optical and spectroscopic diagnostics plasma parameters (density, temperature and expansion velocity) were studied during the accelerating pulse. In the case of explosive emission plasma it was found that the plasma is not uniform and consists of separate plasma spots whose number increases during the accelerating pulse. It was shown that the microwave generation is accompanied by a significant increase in plasma density and ion temperature, up to ∼5·10 16 cm -3 and ∼8 eV, respectively. The plasma electron temperature was found to be ∼8 eV. It was shown that the plasma expansion velocity in the axial direction reaches ∼10 7 cm/s and ≤2·10 5 cm/s in the radial direction. Investigation of the plasma parameters during the magnetron operation with FPS cathode showed also increase of the plasma density up to ∼7·10 14 cm -3 electron and ion temperature up to ∼7 eV and ∼4 eV respectively. It was shown that the application of the ferroelectric plasma cathode allows one to avoid a time delay in the appearance of the electron emission, to achieve better matching between the magnetron and LIA impedances, and to increase significantly (~30%) the duration of the microwave pulse with a ~10% increase in the microwave power. The latter results in generation of microwave radiation to be 30% more efficient than with the use of explosive emission cathode where the efficiency ≤20 %.

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Simulation of rapid startup in microwave magnetrons with azimuthally-varying axial magnetic fields

Cited by 5 publications

References 2 publications

Rapid kinematic bunching and parametric instability in a crossed-field gap with a periodic magnetic field

Rapid kinematic bunching and parametric instability in a crossed-field gap with a periodic magnetic field

Relativistic Magnetron Priming Experiments and Theory

Relativistic magnetron operation with explosive emission and ferroelectric plasma source cathodes

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