Reflections in Gyrotrons With Axial Output

Dumbrājs, O.; Idehara, T.; Watanabe, Shun; Kimura, Atsushi; Sasagawa, Hiroyuki; Agusu, La; Mitsudo, S.; Piosczyk, B.

doi:10.1109/tps.2004.827596

Cited by 21 publications

(6 citation statements)

References 8 publications

(7 reference statements)

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“…For high-power gyrotrons used for plasma heating for fusion applications, the reflections could stem from the output window, the transmission line between the gyrotron and the plasma, or by the first layer of the plasma itself [3]. Reflections can be favorable for gyrotron operation when they are controlled and limited, and have been shown to increase the rf output power [4,5], lock the gyrotron oscillation frequency [6], decrease the sensitivity of the radiation frequency to variation of the magnetic field [2], extend the frequency range by exciting different axial modes [7,8], and suppress parasitic modes [9]. However, when not controlled, even a limited amount of reflection can lead to a complete loss of oscillation by driving the gyrotron to a non-stationary or chaotic phase or into unstable operation in an undesired mode.…”

Section: Introductionmentioning

confidence: 99%

Study of the Effect of Reflections on High-Power, 110-GHz Pulsed Gyrotron Operation

Genoud

Picard

Schaub

et al. 2021

J Infrared Milli Terahz Waves

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The effect of reflection is studied experimentally and theoretically on a high-power 110 GHz gyrotron operating in the TE 22,6 mode in 3 µs pulses at 96 kV, 40 A. The experimental setup allows variation of the reflected power from 0 to 33 % over a range of gyrotron operating conditions. The phase of the reflection is varied by translating the reflector along the axis. Operating at a higher efficiency point, at 4.40 T with 940 kW of output power, reflected power exceeding 11% causes a switch from operation in the TE 22,6 to simultaneous operation in the TE 22,6 and TE 21,6 modes with a large decrease of the total gyrotron output power. This switching effect is in good agreement with simulations using the MAGY code. Operating at a more stable point, 4.44 T with 580 kW of output power, when the reflection is increased, the output power remains in the TE 22,6 mode but it decreases monotonically with increasing reflection, dropping to 200 kW at 33% reflection. Furthermore, at a reflection above 22%, a power modulation at 25 to 30 MHz is observed, independent of the phase of the reflected wave. Such a modulated signal may be useful in spectroscopic and other applications.

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Section: Introductionmentioning

confidence: 99%

Study of the Effect of Reflections on High-Power, 110-GHz Pulsed Gyrotron Operation

Genoud

Picard

Schaub

et al. 2021

J Infrared Milli Terahz Waves

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“…При отсутствии фазовой нелинейности (β ′′ 1 ) свойства собственных частот были исследованы в [15]. Аналогичное уравнение (7) можно получить для частоты второй моды. На рис.…”

Section: основные уравнения и результаты их анализаunclassified

“…При достаточно малых ρ 1 эта зависимость является однозначной (кривая 1). При росте коэффициента отражения число корней уравнения (7), то есть число собственных частот, увеличивается. Соответственно зависимость ω 1 (ψ 1 ) становится неоднозначной (кривая 2).…”

Section: основные уравнения и результаты их анализаunclassified

Влияние Запаздывающих Отражений От Удаленной Нагрузки На Конкуренцию Мод В Гиротроне

2013

AND

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Рассматривается влияние отражений от удаленной нагрузки на конкуренцию мод в двухмодовой модели гиротрона. Анализ проводится на основе квазилинейных уравнений для медленно меняющихся амплитуд мод с кубичной нелинейностью, в которых влияние отражений учтено при помощи слагаемых, содержащих запаздывание. Подробно обсуждается наиболее характерный случай конкуренции двух близких по частоте мод, находящихся в центре зоны генерации. Аналитически и численно исследуется характер смены режимов колебаний при увеличении коэффициента отражения паразитной моды и при различных значениях времени запаздывания.

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“…By placing different reflectors beyond the window and changing the distance between them and the window, one can vary both the magnitude and the phase of the reflection coefficient (see Ref. 7). This simplified scheme might be inaccurate in a real gyrotron, in which, in order to diminish reflection effects, the window can be The output power corresponding to B = 6.86 T is plotted with dashed lines for R el = 9.8 mm, with dots for R el = 9.9 mm and with solid lines for R el = 10.0 mm.…”

Section: Possible Experimentsmentioning

confidence: 99%

Reflections in gyrotrons with radial output: Consequences for the ITER coaxial gyrotron

Dumbrājs¹,

Nusinovich

Piosczyk

2004

Physics of Plasmas

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A theory describing the influence of reflections on operation of gyrotrons with radial output is presented. The theory is used for evaluating the effect of reflections on the operation of the 170 GHz ITER coaxial cavity gyrotron, which is under development in cooperation between EUROATOM Associations (CRPP Lausanne, FZK Karlsruhe, and HUT Helsinki) together with European tube industry (Thales Electron Devices, Velizy, France). It is shown that for optimally chosen external magnetic field value and electron beam radius, possible reflections do not change the final steady-state operation, which corresponds to generation of a 2.2 MW millimeter-wave power. The effect of deviation of the magnetic field and the beam radius from optimal values on the device operation is also studied.

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Reflections in Gyrotrons With Axial Output

Cited by 21 publications

References 8 publications

Study of the Effect of Reflections on High-Power, 110-GHz Pulsed Gyrotron Operation

Study of the Effect of Reflections on High-Power, 110-GHz Pulsed Gyrotron Operation

Влияние Запаздывающих Отражений От Удаленной Нагрузки На Конкуренцию Мод В Гиротроне

Reflections in gyrotrons with radial output: Consequences for the ITER coaxial gyrotron

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