Quasi-stationary convection in a periodic-pulsed optical discharge in high pressure rare gas

Zimakov, V. P.; Кузнецов, В. А.; Solovyov, N. G.; Shemyakin, A. N.; Shilov, A. O.; Yakimov, M. Yu.

doi:10.1088/1742-6596/815/1/012003

Cited by 5 publications

(6 citation statements)

References 9 publications

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“…В работах [19,20] сообщалось о первых экспериментах, в которых наблюдался необычный тип вынужденной конвекции в ИПОР, при которой генерируемый квазистационарный поток был направлен нормально к оси лазерного излучения.…”

Section: влияние лазерно-индуцированной конвекции на стабильность плаunclassified

“…Свечение плазмы было симметричным и стабильным, самыми значительными эффектами были искажение проходящего лазерного луча и потоки газа, направленные в стороны от оптической оси. Причины такого необычного направления потока обсуждались в [20] на основе известных результатов расчетов поздних стадий релаксации облака горячего газа, образующегося при одиночном пробое. Конкретный механизм образования такого потока все еще остается неопределенным.…”

Section: влияние лазерно-индуцированной конвекции на стабильность плаunclassified

“…В данном разделе представлены результаты экспериментов по генерации потоков в ИПОР с использованием фемтосекундного импульсно-периодического лазера. Энергетические характеристики используемого лазера (до 260 мкДж/имп, до 10 кГц частота повторения) близки к характерным величинам в экспериментах [19,20].…”

Section: влияние лазерно-индуцированной конвекции на стабильность плаunclassified

“…В области фокуса в аргоне при 10 бар поглощалось от 35 % до 60 % излучения, в зависимости от настройки (0.3  0.5 Вт или 30  100 мкДж/импульс). Такие уровни выделения энергии в разряде близки к условиям предыдущих экспериментов [19,20]. При таком уровне диссипации энергии за импульс в объеме области ионизации до 10 -7 см 3 газовая температура достигает 10 кK и выше.…”

Section: влияние лазерно-индуцированной конвекции на стабильность плаunclassified

“…Такого рода направленные потоки, вытекающие из зоны разряда, действительно обнаруживались при теневой визуализации картины в окрестности ИПОР. Схемы наблюдения аналогичны применявшимся в [19,20]. В качестве точечного источника излучения высокой яркости для теневого прибора использовался лазерно-плазменный источник типа ЛПИ-50 [22].…”

Section: влияние лазерно-индуцированной конвекции на стабильность плаunclassified

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Spatial and Temporal Instabilities of Optical Discharges

Zimakov¹,

Lavrentyev²,

Solovyov³

et al. 2019

PhChGD

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By now technologies, employing optical discharges find ever expanding applications in metering and diagnostic equipment in science, engineering and medicine. Based on the original experimental results authors look into some manifestations of spatial and temporal instabilities of the continuous and periodic pulse optical discharges (COD, POD). Set of the phenomena considered makes a great impact on a performance of laser produced plasmas essential for many applications, such as high brightness broadband light sources, for instance. Performance instability of continuous optical discharges followed by laser beam refraction on the refraction index gradients exhibit themselves first in spatial inhomogeneity of plasma thermal radiation luminosity and the other parameters related. Spatial inhomogeneity is accompanied by temporal instability of the plasma. The paper reports criteria for the appearance of instabilities related to the refraction followed by the limitations on supporting of elongated plasma. One of the main reasons of temporal instabilities of COD is thermal gravity convection. Instability of a heated gas zone surrounding optical discharge is followed by regular self-sustained oscillations leading in turn to pulsing of brightness and position of radiated plasma. Simple physical model proposed gives estimations correspondent to the observed pulse frequency dependence on gas pressure. In the case of periodic pulse optical discharges forced convection may be put forward as one of the main discharge instability reasons. Pulse optical discharge induces convective flows due to asymmetrical gas expanding following gasdynamical effect of the energy release zone shape determined by laser beam focusing system configuration.

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Section: влияние лазерно-индуцированной конвекции на стабильность плаunclassified

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Spatial and Temporal Instabilities of Optical Discharges

Zimakov¹,

Lavrentyev²,

Solovyov³

et al. 2019

PhChGD

View full text Add to dashboard Cite

show abstract

Research of continuous fiber laser sustained Xe plasma

Wang

Zuo

2022

Vacuum

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Gasdynamic effects in optical discharges produced by periodic pulse femtosecond laser

Lavrentyev

Solovyov

Shemyakin

et al. 2019

J. Phys.: Conf. Ser.

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Quasi-stationary gas streams in argon (10 bar) were observed for the first time being generated by periodic-pulse optical discharge produced by laser pulses of less than 500 fs pulse length with energy up to 200 μJ/pulse and repetition rate 1.66÷10 kHz. Optical discharge was obtained in laser beam focused by off-axis (90°) parabolic mirror. In experiments the shape of the discharge zone was varied accordingly to the laser beam waist shapes varied from astigmatic to non-aberrated ones depending on the parabolic mirror tilt. Intense convective streams flowing out of the discharge volume were observed by schlieren technique. The gas streams produced could be directed normally to the laser beam axis, at some angle to the beam axis or along the beam axis toward the laser or in opposite direction. It was found that the directions of the streams produced, dynamics of their formation and their intensity were governed by the shape of the discharge zone. It was revealed that most intense and fast forming streams produced were directed normally to the laser beam axis. Two opposite streams are induced by the discharge located in astigmatic beam waist in a form of flattened “disk” ∼10 μm thick and ∼100 μm wide. The streams were directed normally to the “disk” surfaces. The energy spent on the gas flow acceleration was estimated to be up to 30% of thermal component of energy dissipated in plasma. When the focusing mirror was aligned to get no astigmatism, the gas flow generated was directed along optical axis toward the laser or backward in some cases. Refraction of the incident laser beam on the refraction index gradients of heated and excited gas injected by backward stream was followed by oscillations of the discharge zone location and generated stream direction. Discharge became stable when the gas streams were co-directional, normal or angled to the laser beam. Further studies are required to define mechanisms and possible applications of the phenomena observed.

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Quasi-stationary convection in a periodic-pulsed optical discharge in high pressure rare gas

Cited by 5 publications

References 9 publications

Spatial and Temporal Instabilities of Optical Discharges

Spatial and Temporal Instabilities of Optical Discharges

Research of continuous fiber laser sustained Xe plasma

Gasdynamic effects in optical discharges produced by periodic pulse femtosecond laser

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