共查询到18条相似文献,搜索用时 125 毫秒
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根据球对称激光等离子体空气冲击波在自由空间中传输的约束条件,对多光子非线性Compton散射的强激光等离子体空气冲击波波前的传输特性进行了研究,给出了散射下空气冲击波波前的运动方程,并进行了数值模拟。结果表明:该冲击波的衰减过程不仅与爆炸源和爆炸过程的特性、释放总能量、空气的弹性有关,而且还与散射有关,散射效应使冲击波的初始半径增大,衰减过程加快,能量转移率提高;数值模拟与实验结果符合得很好。 相似文献
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激光感应等离子体冲击波碎石 总被引:1,自引:0,他引:1
文章对激光感应等离子体冲击波碎石技术的物理机理、发展现状及未来趋势做了综合性评述,并结合作者的实验研究对激光碎石中存在的重要技术问题进行了探讨,同时提出了一些可能的解决办法. 相似文献
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对强飞秒激光聚焦在空气中所激发的等离子体的发射光谱进行了实验研究.结果表明,光谱特征表现为短波段(截至波长为340 nm)强烈的连续谱和长波段(波长在800 nm附近)强度相对较低的线光谱.在脉冲宽度(50 fs)保持不变而不断调节激光脉冲能量时,等离子体光谱形状的特征基本相似;当激光脉冲能量(1 mJ)保持不变而脉冲宽度从50 fs增加至500 fs和1 ps时,连续谱的峰值(500 nm)显得格外突出,并开始呈现出线光谱特征.
关键词:
飞秒激光
激光空气等离子体
发射光谱
线光谱 相似文献
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为了研究激光击穿空气产生的等离子体爆轰波形成机制和传播规律,利用高能量CO2激光器产生强激光,进行了空气中产生激光支持等离子体爆轰波实验。实验中:设置了诱导靶板,用于诱发和定位空气中的激光支持爆轰波;以激光器升压过程球隙放电产生的光信号作为触发源,触发高时间分辨率(纳秒级)的高速相机,记录了激光支持爆轰波的成长和传播全过程。分析了激光支持爆轰波的形成机理和传播规律。采用C-J爆轰理论,计算了激光支持爆轰波的压力和温度。研究结果表明:激光支持等离子体爆轰波形成初期,等离子体爆轰波发光体为球形;随着时间增加,等离子体爆轰波发光体的形状类似流星,且头部为等离子体前沿吸收层,亮度较高,而尾部等离子体温度较低,亮度较弱。等离子体爆轰波高速向激光源的方向移动,爆轰波速度高达18 km/s,温度约为107K。随着激光强度的减弱,爆轰波速度迅速按指数规律衰减,当爆轰波吸收的激光能量不能有效支持爆轰波传播时,爆轰波转变为冲击波。 相似文献
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将高功率脉冲激光作用于金属元靶产生等离子体,实验测试了并分析了靶上电势信号的时间演变规律及其成因,同时实验研究了激光能量、靶材料、靶结构等因素对靶上电势信号的影响. 相似文献
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研究对比了激光直接辐照、聚焦辐照以及激光等离子体辐照三种辐照方式下,洋葱表皮细胞的烧蚀特征,并基于激光辐照的热力学特性对细胞的温升以及相变过程进行分析。观察发现: 直接辐照对细胞的杀伤效果很不明显;聚焦辐照会引起焦点附近细胞的断裂以及脱水;激光等离子体辐照作用下,细胞会呈现大面积的去除,断裂边缘粗糙,且细胞层有叠加现象。理论分析发现,激光等离子体具有热效应、辐射电离及冲击波效应等,会增加激光脉冲能量到细胞的沉积、以及对细胞冲击剥离等,从而会大大增加细胞的杀伤范围和效率,可用于对细胞进行大面积杀伤。 相似文献
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The evolution of shock waves produced by 7 ns laser pulses in air is
investigated by time-resolved shadowgraph. A nodular structure of
the shock wave is observed. It is found that the origin of the
structure is the multi-longitudinal-microfocus caused by the
astigmatism of the laser beam. The spherical shock waves formed by
each microfocus expand gradually and collide with each other,
resulting in the nodular structure of the shock wave. 相似文献
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A theoretical model is proposed to describe the mechanism of
laser-induced plasma shock wave evolution in air. To verify the
validity of the theoretical model, an optical beam deflection technique
is employed to track the plasma shock wave evolution process. The
theoretical model and the experimental signals are found to be in
good agreement with each other. It is shown that the laser-induced
plasma shock wave undergoes formation, increase and decay processes;
the increase and the decay processes of the laser-induced plasma
shock wave result from the overlapping of the compression wave and
the rarefaction wave, respectively. In addition, the laser-induced
plasma shock wave speed and pressure distributions, both a
function of distance, are presented. 相似文献
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基于聚偏二氟乙烯压电传感器, 对铜靶材中纳秒激光脉冲诱导的冲击波传播过程进行了实验研究, 给出了铜靶材内冲击压强随激光脉冲能量和靶材厚度的变化规律. 实验结果表明: 500 mJ激光脉冲能量作用到2 mm厚的铜靶材产生的冲击压强达到2.1 MPa; 激光脉冲能量从200 mJ 增加到500 mJ, 在铜靶材厚度为2和4 mm条件下, 冲击压强分别增加了162%和231%; 而当铜靶材厚度从2 mm增加到6 mm时, 在400和500 mJ激光脉冲能量作用下, 铜靶材内冲击压强分别降低了32%和49%. 相似文献
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Abstract Shock-wave studies have made it possible to obtain data on the compressibility of more than 200 materials at standard conditions, in solid, liquid and gaseous states, including about 50 It has been found that the functions of atomic volumes of elementary substances versus the atomic number have a periodic forms. This periodicity is related with the electron shell structure of atoms. A flattening of curves versus a pressure increase and growth of compressibility of substances with large atomic volumes are observed. This phenomenon is related with the reconstruction of the electron structure: the atoms are drawing together under compression and the energy exchange is increasing. It leads to broadening and overlapping of electron energy levels. The pressure range up to several megabars has been studied in detail under laboratory conditions. At these pressures electron structure changes of substances having an inverse population may take place. Transitions of outer A-electrons into vacant d-levels are the most prevailing ones under compression. Closed internal configurations characterized by an essentially lower compressibility appear. The treatment of shock-wave experiments results has shown the inflections of shock adiabats at pressures of some hundred kilobars in some cases', which was related with the completion of above-mentioned transitions. There are contradictions in this interpretation of experimental results. So most of metals of the fourth group are characterized by the most closely packed atom structures and therefore it is impossible to explain a sharp reduction of the compressibility with respect to transition to the close-packed phases; we have failed to find the hypothesis-predicted bend on the shock-wave adiabat of pottasium. Furthermore most of inflections have not been confirmed by later experimental researches3. According to Ref. 3 the inflections of three materials are expressed considerably weaker and not at the same values of particle velocity as compared with Ref. 1. In the procedure of the treatment of experimental results' there is an inconsistency which is typical for many early researches. In our opinion this inconsistency has led to an appearance of the shock adiabat inflections for some substances. We shall explain the above said in detail now. 相似文献
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Ion-acoustic shock waves and their head-on collision in a dense electron-positron-ion quantum plasma
Jiu-Ning Han Long HeNing-Xuan Yang Zhen-Hai HanXin-Xing Wang 《Physics letters. A》2011,375(43):3794-3800
Ion-acoustic shock waves and their head-on collision in a dense quantum plasma comprised of electrons, positrons, and ions are studied. The extended Poincaré-Lighthill-Kuo perturbation method is used to derive the Korteweg-de Vries-Burgers equations for shock waves in this plasma. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. The effects of the ratio of positrons to ions unperturbation number density μ, the normalized kinematic viscosity ηi0, and the quantum Bohm potential H on the interaction and structure of the shock waves are investigated. It is found that there are integrally vertical downward movements for both the colliding shocks after their head-on collision, but there are no shifts of the postcollision trajectories (phase shifts). It is also found that these plasma parameters can significantly influence the collision and properties of the colliding shocks. The results may have relevance in dense astrophysical plasmas (such as neutron stars or white dwarfs) as well as in intense laser-solid density plasma experiments. 相似文献
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SpatialandtemporalstudyofshockwavesgeneratedbylaserablationforTitargetWUJiada;WULinghui;WUChangzheng;LIFuming(StateKeyJointLa... 相似文献
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The propagation of light waves in an underdense plasma is studied using one-dimensional Vlasov-Maxwell numerical simulation.It is found that the light waves can be scattered by electron plasma waves as well as other heavily and weakly damping electron wave modes,corresponding to stimulated Raman and Brilluoin-like scatterings.The stimulated electron acoustic wave scattering is also observed as a high scattering level.High frequency plasma wave scattering is also observed.These electron electrostatic wave modes are due to a non-thermal electron distribution produced by the wave-particle interactions.The collision effects on stimulated electron acoustic wave and the laser intensity effects on the scattering spectra are also investigated. 相似文献