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1.
采用蒙特-卡罗(Monte Carlo)模拟方法,研究了初始溅射粒子密度对其传输中的密度和速度分布以及环境气体密度分布的影响.结果表明,随着初始溅射粒子密度增大,烧蚀粒子和环境气体高密度峰的交叠区离开靶的最大距离减小,被衬底反弹后,距靶的最小距离减小,烧蚀粒子的速度分布随初始溅射粒子密度增大而变宽,当初始溅射粒子密度大于8.33×1025 m-3时,出现速度劈裂现象.所得结论为进一步定量研究纳米晶粒的成核机理提供了基础. 关键词: Monte Carlo模拟 烧蚀粒子 密度分布 速度分布  相似文献   

2.
在背景气压为8× 10-3— 100Pa范围内 ,通过测量脉冲激光烧蚀平面Al靶产生的等离子体辐射谱的时间分辨特征 ,比较空间不同点辐射的飞行时间轮廓的相对延迟 ,从而得到辐射粒子速度及其空间分布 .利用绝热膨胀的理论和激波模型分别对背景气压小于 0 .6Pa的结果和 5Pa时的结果作了分析 ,并得出激波的波面基本上为柱对称. With the ambient gas pressure in the range from 8×10 -3 to 10 2 Pa, Q-switched YAG laser ablates plane aluminum target and plasma are produced. Optical emission spectroscopy is used to carry out time-resolved analysis of atomic particles. Using the resonance transition of Al I 396.1 nm (3p 2P-4s 2S), the spatiol velocity distribution of Al I has been obtained under the laser energies of 160 mJ/pulse when the ablating size is about 200 μm. The velocity is at the order of 10 6 cm/s...  相似文献   

3.
利用一维辐射流体动力学程序MULTI数值模拟研究了功率为1014W/cm2、脉冲宽度为1ns、波长为0.35μm的短脉冲强激光辐照不同厚度的平面Au靶时,靶厚度对靶背面x射线能谱结构和辐射强度的影响. 关键词: 激光等离子体 辐射流体力学 x射线转换  相似文献   

4.
激光聚变物理实验中,背光透视照相是靶丸内爆动力学过程观测的重要方法. Ag是一种重要的背光材料, 激光辐照产生的等离子体可以产生强L线辐射, 研究其烧蚀和辐射特性, 对提高内爆靶丸背光透视照相的图像质量具有十分重要的意义.在神光II装置上, 采用第九路输出的2 ns, ~ 5× 1014 W/cm2, 526.5 nm激光均匀辐照Ag薄膜靶, 实验研究了其烧蚀特性, 获得了银薄膜靶在激光烧蚀驱动下的飞行轨迹和飞行速度的数据. 实验结果与一维辐射流体力学模拟结果相符. 火箭模型对实验数据进行拟合, 得到了Ag材料的质量烧蚀速率和烧蚀压的数据. 采用平面晶体谱仪和X射线二极管探测器阵列观测等离子体的辐射特性, 获得了Ag等离子体辐射光谱和L线转换效率, 实验结果对激光聚变内爆靶丸背光照相的实验设计具有重要的参考价值.  相似文献   

5.
周磊  李晓亚  祝文军  王加祥  唐昌建 《物理学报》2016,65(8):85201-085201
提出一种通过诊断等离子体反冲动量来计算激光加载产生冲击压强的方法. 当强激光辐照固体靶表面时, 所产生的高速喷射的等离子体对靶具有反冲作用, 通过诊断等离子体反冲动量的变化可以计算激光辐照固体靶产生的冲击压强变化. 本文利用辐射流体力学软件研究了这种诊断方法, 模拟采用的激光功率密度为5×1012-5×1013 W/cm2, 激光脉宽选取纳秒量级. 模拟结果表明该方法是有效且可行的.  相似文献   

6.
5—200?范围激光等离子体X射线辐射特性研究   总被引:1,自引:0,他引:1       下载免费PDF全文
利用带有针孔的透射式光栅光谱仪研究了激光等离子体X射线辐射的原子序数依赖性和激光功率密度对辐射的影响。得到了波长为1.06μm,平均功率密度为5×1014W/cm2的激光辐照条件下Z=6(C)到Z=79(Au)的不同原子序数激光等离子体X射线发射光谱。点聚焦和线聚焦激光照射方式下Al,Au等离子体X射线发射的对照实验结果表明,激光功率密度对低Z等离子体X射线发射的影响比对高Z的影响更明显。 关键词:  相似文献   

7.
利用针孔透射光栅光谱仪(PTGS)研究了波长为1.06μm、平均功率密度为2×1012W/cm2的线聚焦激光照射Al平板靶所产生的线状等离子体的轴向和非轴向X射线发射(5—200?)的光谱和空间分布特性。文中也就该条件下的线状等离子体作为X射线激光增益介质的有关问题进行了讨论。 关键词:  相似文献   

8.
利用“星光Ⅱ”高功率激光装置三倍频激光(波长0.35μm,能量5—90J,焦斑直径约200μm,脉冲宽度400—800ps)辐照多种材料(C,Al,Cu,Au)靶,对于不同激光功率密度,研究软X射线转换和发射能谱.结合0.35μm激光辐照Al靶的质量烧蚀率和等离子体喷射速度与激光功率密度的定标关系进行数值模拟,对于激光功率在1013—1015W/cm2理论模拟结果与实验结果符合得很好 关键词:  相似文献   

9.
介绍了激光加热Cu靶和NaF靶发射的在1.2keV区X射线转换效率的测量方法和实验结果。结果表明,在激光辐照功率密度为1×1013—1×1014W·cm-2条件下,激光波长为1.06μm或0.53μm时,Cu等离子体发射的1.2KeV区X射线的转换率为NaF等离子体的4—5倍;对此两种等离子体,激光波长为0.53μm的X射线转换效率是波长为1.06μm的2倍左右。 关键词:  相似文献   

10.
本文提出一种软X射线条纹相机与吸收膜相耦合测量激光等离子体辐射温度的实验方法,并且应用这个方法测量了平面金靶在1.053μm激光(LF-11#激光装置)作用下,靶面功率密度约为1014W/cm2的辐射温度。对温度处理中存在的误差,以及把此方法推广到能谱的时间分辨和温度的空间分辨测量中的可能性进行了讨论。 关键词:  相似文献   

11.
2 Cu3O7, using a Q-switched Nd:YAG laser is investigated by time-resolved emission-spectroscopic techniques at various laser irradiances. It is observed that beyond a laser irradiance of 2.6×1011 W cm-2, the ejected plume collectively drifts away from the target with a sharp increase in velocity to 1.25×106 cm s-1, which is twice its velocity observed at lower laser irradiances. This sudden drift apparently occurs as a result of the formation of a charged double layer at the external plume boundary. This diffusion is collective, that is, the electrons and ions inside the plume diffuse together simultaneously and hence it is similar to the ambipolar diffusion of charged particles in a discharge plasma. Received: 30 January 1998/Revised version: 12 June 1998  相似文献   

12.
The spectra and dynamics of the line emission of a lead erosion laser plasma at a distance of 1 mm from the target are investigated. The plasma is ignited in a vacuum (P=3–12 Pa) with a pulse-periodic neody-mium laser (τ=20 ns, f=12 Hz, W=(1–2)×109 W/cm2, and λ=1.06 µm). The data obtained are used to analyze the emission dynamics and the mechanism of formation of the laser plume.  相似文献   

13.
Gold nanorods manifest a readily tunable longitudinal plasmon resonance with light and consequently have potential for use in photothermal therapeutics. Recent work by others has shown how gold nanoshells and rods can be used to target cancer cells, which can then be destroyed using relatively high power laser radiation (∼1×105 to 1×1010 W/m2). Here we extend this concept to demonstrate how gold nanorods can be modified to bind to target macrophage cells, and show that high intensity laser radiation is not necessary, with even 5×102 W/m2 being sufficient, provided that a total fluence of ∼30 J/cm2 is delivered. We used the murine cell line RAW 264.7 and the monoclonal antibody CD11b, raised against murine macrophages, as our model system and a 5 mW solid state diode laser as our energy source. Exposure of the cells labeled with gold nanorods to a laser fluence of 30 J/cm2 resulted in 81% cell death compared to only 0.9% in the control, non-labeled cells.  相似文献   

14.
Single-walled carbon nanotubes (SWCNTs) are synthesized by the ablation of a catalyst-containing carbon target with a cw CO2 laser. Emphasis is on ablation conditions that are favorable to self-organized SWCNT synthesis. It is shown that the graphite target intensely evaporates with the formation of fractal-like tubes at the edge of the jet when the laser power density exceeds 105 W/cm2. Still more favorable conditions for carbon nanotube synthesis are set if the power density lies within 2×104–5×104 W/cm2. Under these conditions, both individual SWCNTs and their bundles of diameter from 1.1 to 1.5 nm are produced, as shown by Raman scattering and electron microscopy studies. In this series of experiments, the maximal fraction of SWCNTs reaches 20%. A mechanism of SWCNT fast growth in the laser torch is suggested.  相似文献   

15.
A new candidate laser dye based 1,4-bis[β-(2-naphthothisolyl) vinyl] benzene (BNTVB) were prepared, and characterized in various organic solvents. The center polarity is less sensitive than electronic absorption. A red shift was noticed in the fluorescence spectra (ca. 40 nm) with increment in the solvent’s polarity, this means that BNTVB’s polarity appreciates upon excitation. The dipole moment of ground state (μg) and the excited singlet state dipole moment (μe) are determined from Kawski – Chamma and Bakshiev–Viallet equations using the disparity of Stokes shift with solvent polarity function of ε (dielectric constant) and n (refractive index) of the solvent. The result was found to be 0.019D and 5.13D for ground and exited state, in succession. DFT/TD-DFT manners were used to understand the electronic structures and geometric of BNTVB in other solvents. The experimental and theoretical results showed a good agreement. The photochemical quantum yield (Фc) of BNTVB was calculated in variable organic reagents such as Dioxane, CHCl3, EtOH and MeOH at room temperature. The values of φc were calculated as 2.3?×?10?4, 3.3?×?10?3, 9.7?×?10?5 and 6.2?×?10?5 in Dioxane, CHCl3, EtOH and MeOH, respectively. The dye solutions (2?×?10?4 M) in DMF, MeOH and EtOH give laser emission in the blue-green region. The green zone is excited by nitrogen pulse 337.1 nm. The tuning range, gain coefficient (α) and cross – section emission (σe) of laser were also estimated. Excitation energy transfer from BNTVB to rhodamine-6G (R6G) and N,N-bis(2,6-dimethyphenyl)-3,4:9,10-perylenebis-(dicarboximide) (BDP) was also studied in EtOH to increase the laser emission output from R6G and BDP when excited by nitrogen laser. The dye-transfer power laser system (ETDL) obeys the Foster Power Transmission (FERT) mechanism with a critical transmission distance, Ro of 40 and 32 ? and kET equals 2.6?×?1013 and 1.06?×?1013 M?1 s?1 for BNTVB / R6G and BNTVB / BDP pair, respectively.  相似文献   

16.
红外激光对可见光CCD成像系统的干扰   总被引:5,自引:1,他引:4       下载免费PDF全文
采用连续波红外激光对可见光面阵CCD成像系统进行了干扰实验,观察到饱和串扰、全屏饱和等干扰现象,并测到串扰阈值小于2.0×102W/cm2,全屏饱和阈值为1.2×104W/cm2。通过分析CCD输出电压、视频信号,提出基于有效干扰面积的干扰效果评估方法,并利用该方法对干扰面积与激光功率密度、辐照时间之间的关系进行了半定量分析。结果显示:激光功率密度对干扰效果的影响较大,而辐照时间在0.5~2.0 s之间时,辐照时间对CCD干扰效果的影响不明显。  相似文献   

17.
Here, we report the fabrication of diamond-like carbon (DLC) thin films using pulsed laser deposition (PLD). PLD is a well-established technique for deposition of high-quality DLC thin films. Carbon tape target was ablated using a KrF (248 nm, 25 ns, 20 Hz) excimer laser to deposit DLC films on soap-coated substrates. A laser fluence between 8.5 and 14 J/cm2 and a target to substrate distance of 10 cm was used. These films were then released from substrates to obtain freestanding DLC thin foils. Foil thicknesses from 20 to 200 nm were deposited using this technique to obtain freestanding targets of up to 1-inch square area. Typically, 100-nm-thick freestanding DLC films were characterized using different techniques such as AFM, XPS, and nano-indentation. AFM was used to obtain the film surface roughness of 9 nm rms of the released film. XPS was utilized to obtain 74 % sp2, 23 % sp3, and 3 % C–O bond components. Nano-indentation was used to characterize the film hardness of 10 GPa and Young’s modulus of 110 GPa. Damage threshold properties of the DLC foils were studied (1,064 nm, 6 ns) and found to be 7 × 1010 W/cm2 peak intensity for our best ultrathin DLC foils.  相似文献   

18.
The irradiation of Nd:Y2O3 targets with an absorption coefficient of 13–1.7 × 103 cm?1 using laser pulses with a duration of 0.1–3.5 ms and peak power of 200–700 W at a power density of (0.2–1.3) × 106 W/cm2 is studied. A relatively large spread of the delay times of laser plume, spike emission of the laser plume, cleavage of the front surface of the target, and greater ejection of substance from the crater in comparison with the effect of the CO2-laser radiation with almost the same power are demonstrated. A numerical model of the effect of radiation on a target with a nonuniform refractive index is proposed to interpret the destruction of dielectric material (cleavage of the front surface) and the large spread of the delay times of the plume.  相似文献   

19.
A Nd:YAG laser operating at the fundamental wavelength (1064 nm) and at the second harmonic (532 nm), with 9 ns pulse duration, 100–900 mJ pulse energy, and 30 Hz repetition rate mode, was employed to ablate in vacuum (10?6 mbar) biomaterial targets and to deposit thin films on substrate backings. Titanium target was ablated at the fundamental frequency and deposited on near-Si substrates. The ablation yield increases with the laser fluence and at 40 J/cm 2 the ablation yield for titanium is 1.2×1016 atoms/pulse. Thin film of titanium was deposited on silicon substrates placed at different distance and angles with respect to the target and analysed with different surface techniques (optical microscopy, scanning electron spectrosopy (SEM), and surface profile).

Hydroxyapatite (HA) target was ablated to the second harmonic and thin films were deposited on Ti and Si substrates. The ablation yield at a laser fluence of 10 J/cm 2 is about 5×1014 HA molecules/pulse. Thin film of HA, deposited on silicon substrates placed at different distance and angles with respect to the target, was analysed with different surface techniques (optical microscopy, SEM, and Raman spectroscopy).

Metallic films show high uniformity and absence of grains, whereas the bio-ceramic film shows a large grain size distribution. Both films found special application in the field of biomaterial coverage.  相似文献   

20.
This paper presents the construction, use and characterisation of a laser-induced sealed plasma shutter to clip off the nitrogen pulse tail of a CO2-TEA laser-based lidar dial system. Investigation of the optimum gas filling pressure, temporal profile of the clipped pulse, and the laser threshold power intensities to achieve ionisation growth and breakdown in helium, argon, and nitrogen are also presented. Values of these power density thresholds lie between 3×1011 W cm-2–5×1012 W cm-2, 2×1011 W cm-2–2×1012 W cm-2 and 3×1013 W cm-2–2×1014 W cm-2 for helium, argon, and nitrogen, respectively. The range resolution attainable with the present clipped pulses is 15 m, which is 30 times better than that readily obtained with the nitrogen-tailed pulses. Field measurements of the lidar returns with the clipped pulse from a co-operative target are presented. Received: 27 December 1999 / Revised version: 11 February 2000 / Published online: 27 April 2000  相似文献   

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