Thermo-electron accumulation in light and heavy water during MHz-burst laser ablation
Laser-induced water ablation triggers various physical effects, including atom ionization, optical breakdown of the liquid, phase explosion, cavitation, and shockwave propagation. These effects can be further amplified in heavy water by deuterium-deuterium fusion reactions, which require extremely h...
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Main Authors | , , , |
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Format | Journal Article |
Language | English |
Published |
05.09.2024
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Subjects | |
Online Access | Get full text |
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Summary: | Laser-induced water ablation triggers various physical effects, including
atom ionization, optical breakdown of the liquid, phase explosion, cavitation,
and shockwave propagation. These effects can be further amplified in heavy
water by deuterium-deuterium fusion reactions, which require extremely high
energy levels. Laser pulses can be grouped in bursts to achieve the necessary
energy within the ablation plasma plume. This study aims to compare the
ablation plasma glow and thermal effects in light and heavy water under both
single-pulse and burst-mode ultrashort laser irradiation. Notably, this
research introduces the novel application of burst laser ablation in heavy
water for the first time. The ablation was conducted beneath the water surface
along a circular, laser-scanned trajectory, with two distinct ablation regimes:
burst mode and single-pulse mode, utilizing lenses with varying focal lengths
and different pulse durations. Absorption processes and plasma glow were
monitored using visible and infrared detectors, a fast silicon detector, and a
thermocouple.
The study revealed that the burst regime in heavy water produced the most
intense plasma glow when 1 ps laser pulses were used, with shorter pulses
yielding less intense glow and the longest pulses yielding the least.
Surprisingly, plasma glow at a lower initial power density of 2.6e13 W/cm2 was
four times higher than at a higher power density of 8e13 W/cm2. These findings
were compared with existing theories on plasma formation in water by ultrashort
laser pulses. The observed increase in pulse-to-pulse plasma glow in burst mode
was attributed to thermo-electron accumulation effects. The density of excited
and hydrated electrons was calculated using both strong-field ionization and
avalanche ionization models. Additionally, the influence of pulse parity on
burst ablation glow in heavy water was discussed. |
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DOI: | 10.48550/arxiv.2409.03311 |