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本文研究了在自由振荡钕玻璃激光照射下LY12铝靶产生喷溅的物理机制及特性。这种幅度与时间无规律变化的激光序列尖峰脉冲的单个脉冲宽度约2μs,脉冲间隔约5μs。在这些脉冲作用下产生的喷溅过程也呈现相应的序列特性。在10^7W/cm^2的激光平均功率密度下,个别的尖峰脉冲功率密度可大于10^8W/cm^2。用分幅和扫描高速相机分别测量速度较低的喷溅物汽化运动图象,观察到了以7.7mm/μs的速度逆着入射激光方向传播的靶蒸汽和等离子体的喷溅过程,这相应于激光吸收波现象,并发现有屏蔽效应。 相似文献
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实验研究了样品表面有切向空气气流、切向氮气气流和无气流时,976 nm连续激光对玻璃纤维增强E-51环氧树脂复合材料的辐照效应。结果表明:无气流时,喷出的热分解产物会对入射激光产生屏蔽作用;有气流时,激光对玻璃纤维的破坏方式是其升温熔化后再被切向气流带走;当激光功率密度较低时,切向空气气流以加强样品表面的对流冷却作用为主,不利于激光对玻璃纤维复合材料的破坏;当激光功率密度较高时,切向空气气流以降低屏蔽作用和提供氧气助燃为主,有利于激光对玻璃纤维复合材料的破坏。三种气流状态下,质量损失随功率密度呈现单调增加趋势,当入射激光功率密度在100~600 W/cm2范围内,随着功率密度的增大,激光能量的利用效率逐渐增大并趋于稳定。 相似文献
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《光学学报》2017,(9)
在全面分析碱金属蒸气激光放大器的激光动力学与流体动力学过程的基础上,结合热效应、饱和放大效应、放大自发辐射、高能级激发与电离的影响,建立了一个相对完善的物理模型来模拟流动散热条件下半导体抽运碱金属蒸气激光放大器的输出特性。计算模拟了纵向和横向两种不同流动方式下,气体流速对输出功率的影响,比较分析了高抽运功率密度下各能级粒子数密度的变化趋势,最后模拟了各级放大器的功率分配比对提高级联放大器输出效率的作用。结果表明:在相同工作温度条件下,多个等长蒸气池和均等抽运光功率分配能让高级数放大器获得比低级数放大器更高的放大倍数。所提模型有助于高功率碱金属蒸气激光放大器的参量选择和优化设计。 相似文献
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运用热化学分析、扫描电子显微技术等手段,分析了碳纤维增强环氧树脂基复合材料在ms量级重频激光辐照下的损伤形式,研究了峰值功率密度、辐照时间、重复频率和脉冲宽度等对复合材料烧蚀规律的影响。研究结果表明:在激光辐照过程中,复合材料树脂基体在300 ℃开始裂解;由于裂解气体的保护作用,碳纤维不发生氧化,而是在汽化点(3 300 ℃)汽化烧蚀;复合材料热烧蚀率随峰值功率密度和重复频率提高而增大,随辐照时间增加而减小,最终均趋于定值;增加脉冲宽度可以提高辐照区峰值温度,降低碳纤维损伤的功率密度阈值。 相似文献
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《光学技术》2015,(4):327-330
应用Compton散射模型、平均原子模型和碰撞-辐射模型,研究了超强激光等离子体推进机制,提出了将入射光和Compton散射光作为超强激光等离子体推进新机制,给出了束缚电子占据概率和流体力学修正方程,得到了O、Ne、N、Xe的等离子体烧蚀压、等效烧蚀深度和烧蚀速度随入射激光功率密度变化的模拟结果。结果表明:与散射前相比,随着激光功率密度增大,Xe烧蚀压最大,其次是Ne、O、N;O等效烧蚀深度最大,其次是N、Xe、Ne;Ne弛豫时间最长,其次是O、N、Xe;Xe烧蚀速度最快,其次是Ne、O、N。采用含电子多的轻元素超强激光等离子体,有利于等离子体整体推进。 相似文献
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Laser material processing involving welding, ablation and cutting involves interaction of intense laser pulses of nanosecond
duration with a condensed phase. Such interaction involving high brightness radiative flux causes multitude of non-linear
events involving thermal phase transition at soild-liquid-gas interfaces. A theoretical perspective involving thermal dynamics
of the vaporization process and consequent non-linear multiple thermal phase transitions under the action of laser plasma
is the subject matter of the present work. The computational calculations were carried out where titanium (Ti) was treated
as a condensed medium. The solution to the partial differential equations governing the thermal dynamics and the underlying
phase transition event in the multiphase system is based on non-stationary Eulerian variables. The Mach number M depicts significant fluctuations due to thermal instabilities associated with the laser beam flux and intensity. A conclusive
amalgamation has been established which relates material surface temperature profile to laser intensity, laser flux and the
pressure in the plasma cloud.
相似文献
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激光感生等离子体特性的三维数值模拟 总被引:1,自引:0,他引:1
在激光焊接过程中,作用于金属工件表面的高强度激光会引起材料的强烈蒸发,金属蒸汽与入射激光相互怍用,又会引起金属蒸汽部分电离,形成激光感生等离子体。本文采用三维模拟方法,考虑保护气和侧吹气的影响,对激光感生等离子体中的温度与速度分布进行了研究。 相似文献
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S.I. Anisimov N.A. Inogamov A.M. Oparin B. Rethfeld T. Yabe M. Ogawa V.E. Fortov 《Applied Physics A: Materials Science & Processing》1999,69(6):617-620
Theoretical study of laser ablation is usually based on the assumption that the vapor is an ideal gas. Its flow is described
by gas dynamics equations [1, 2]. The boundary conditions at vaporization front are derived from the solution of the Boltzmann
equation that describes the vapor flow in the immediate vicinity of the vaporizing surface (so-called Knudsen layer) [1].
This model is applicable within the range of temperatures much lower than the critical temperature of target material. In
the present work, a general case is considered when the temperature of the condensed phase is comparable to or higher than
the critical temperature. The dynamics of both condensed and gaseous phases can be described in this case by the equations
of hydrodynamics. The dynamics of vaporization of a metal heated by an ultrashort laser pulse is studied both analytically
and numerically. The analysis reveals that the flow consists of two domains: thin liquid shell moving with constant velocity,
and thick low-density layer of material in two-phase state.
Received: 2 March 1999 / Accepted: 28 May 1999 / Published online: 21 October 1999 相似文献
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在原子法激光同位素分离工程中,电子枪加热金属铀产生的原子蒸气的密度、速度以及温度等宏观量分布特性是非常重要的参数.为了分析电子枪功率和束宽对原子蒸气密度、速度、温度、质量通量和速度分布等物理特性的影响,采用直接MonteCarlo方法用柱坐标模拟了铀原子平面蒸发动力学过程.在电子枪加热方式下,蒸发源温度场不均匀,而且温度场随电子枪功率和束宽变化.着重研究这种变化对蒸气各种物理特性的影响.模拟结果表明,电子枪功率越高,蒸气径向宏观漂移速度越大,蒸发量越大;电子束束宽越窄,蒸发量越大.
关键词:
金属蒸发
原子法激光同位素分离
直接MonteCarlo
电子枪 相似文献
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从理论仿真计算方面开展了脉冲激光诱导CCD探测器铝层金属温升变化的液-固相变时间特性研究。通过傅里叶热传导方程计算仿真了纳秒激光诱导CCD探测器铝层金属材料的温升曲线,获得了铝层金属材料液-固相变起始时刻和液-固相变时间长度随激光脉冲峰值功率和激光入射角度的变化规律。理论计算结果表明,随着入射激光脉冲峰值功率增加,激光诱导CCD探测器铝层表面的最高温度逐渐升高,铝层材料的液-固相变起始时刻往后延迟,且液-固相变时间长度增加;随激光入射角度的增大,铝层表面的最高温度逐渐降低,液-固相变起始时刻不断前移,而液-固相变时间长度逐渐变短。研究结果表明,激光脉冲峰值功率密度和激光入射角对激光诱导CCD探测器的液-固相变时间特性有重要影响,对揭示纳秒激光诱导CCD探测器的热损伤机制有重要的理论意义。 相似文献
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This work investigates evaporation kinetics -- the relation between the surface temperature and pressure during excimer laser ablation. Nickel targets are ablated by excimer laser pulses in a laser fluence range between 1 and 6 J/cm2, with the upper limit exceeding the threshold of phase explosion (5 J/cm2). The surface pressure is determined with a polyvinylidene fluoride (PVDF) piezoelectric transducer. When phase explosion occurs, the surface temperature is known to be near the thermodynamic critical temperature, therefore, by measuring the surface pressure, the surface temperature-pressure relation is determined at the threshold fluence of phase explosion. The surface temperature and the threshold fluence of phase explosion are also estimated from the measured velocity of the vapor plume and gas dynamics calculations. It is shown that, during excimer laser ablation, the temperature and pressure relation deviates significantly from the equilibrium kinetic relation. 相似文献
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根据高功率二极管激光器的散热需求,设计了一种储能式相变冷却实验系统,并开展了喷雾相变冷却器和微通道相变冷却器的设计。采用多孔微结构的换热表面,用氨做制冷剂,实现了喷雾相变冷却器表面温度37 ℃时,散热功率密度达到了511 W/cm2。采用节流汽化原理,分别设计了背冷式相变微通道冷却器和薄片型的模块式相变微通道冷却器,背冷式相变微通道冷却器采用氨做制冷剂, 散热功率密度达到了550 W/cm2,采用R124做制冷剂,散热功率密度约270 W/cm2。采用R124做制冷剂,实现了脉冲激光功率3 kW和连续激光功率100 W的相变冷却二极管激光器模块封装。 相似文献
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研究了高能短脉冲激光薄膜制备的整个烧蚀过程.首先建立了基于超热理论的烧蚀模型,然 后利用较为符合实际的高斯分布表示脉冲激光输入能量密度,给出了考虑蒸发效应不同阶段 的烧蚀状态方程.结合适当的边界条件,以Si靶材为例,利用有限差分法得到了靶材在各个 阶段温度随时间和烧蚀深度的演化分布规律及表面蒸发速度与烧蚀深度在不同激光辐照强度 下随时间的演化规律.结果表明,在脉冲激光辐照阶段,靶材表面的蒸发效应使得靶材表面 温度上升显著放缓;在激光辐照强度接近相爆炸能量阈值时,蒸发速度与蒸发厚度的变化由 于逆流现象将显著放缓.还得到了考虑了熔融弛豫时间及蒸发效应的固-液界面随时间的演化 方程,这一结论较先前工作更具有普适性.
关键词:
脉冲激光烧蚀
热流方程
温度演化
有限差分法 相似文献
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We present the most important results of investigations of lasers based on vapors and solutions of complex organic compounds.
We investigated the effect of a foreign gas, the duration and intensity of the exciting pulse, the temperature of the active
medium, and the spectroscopic parameters of the material on the generation characteristics of complex molecules in the gas
phase. The special features of generation of radiation by a laser with distributed feedback in transition from a condensed
to the gas phase in heating the active medium are considered. It is suggested that the polarization characteristics of the
radiation generated by a vapor laser be used to investigate the laws that govern the relaxation of optically induced anisotropy
of excited molecules of the active medium.
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 709–720, September–October, 1998. 相似文献