共查询到20条相似文献，搜索用时 31 毫秒
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本文报道一种高灵敏飞秒时间分辨光偏转波谱技术。利用这一技术我们探测到锗薄片内超快的声子激发并精确测量了声脉冲的波形。我们观测到了光激发的电子—空穴等离子的超声传播。从实验数据我们推算出等离子的传播速度是锗内纵向声速的4倍。 相似文献
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N. A. Inogamov A. Ya. Faenov V. V. Zhakhovskii I. Yu. Skobelev V. A. Khokhlov Y. Kato M. Tanaka T. A. Pikuz M. Kishimoto M. Ishino M. Nishikino Y. Fukuda S. V. Bulanov T. Kawachi Yu. V. Petrov S. I. Anisimov V. E. Fortov 《等离子体物理论文集》2011,51(4):361-366
Laser‐matter interaction is defined by an electronic band structure of condensed matter and frequency ωL of electromagnetic radiation. In the range of moderate fluences, the energy absorbed by electrons from radiation finally thermalizes in the ion thermal energy. The thermalization processes are different for optical as compared with X‐ray quanta and for metals relative to semiconductors and dielectrics, since the light absorption and electron‐electron, electron‐ion dynamics are sensitive to the electron population in a conduction band and the width of a forbidden gap. Although the thermalization processes are different, the final state is simply a heated matter. Laser heating creates powerful stresses in a target if duration of a laser pulse τL is short in acoustic time scale. Nucleation and material removal take place under such stresses. Such way of removal is called here the spallative ablation. Thus the spallative ablation is an ablation mechanism universally important for qualitatively different materials and quanta (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The analysis of influence of the inhomogeneous distribution of temperature and density of atoms on the probability of absorption of ultrashort electromagnetic pulses in plasma is carried out. A specific example of divertor plasma of tokamaks and absorption in the Lyman series (at the Ly-α line) is considered. It is shown that the absorption probability may exceed relative populations of excited levels in divertor plasma by several orders of magnitude. The influence of the pulse duration on the probability of excitation of an atomic level is considered. The results suggest a possibility of a sharp increase in a fluorescence signal under the action of an ultrashort pulse. 相似文献
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给出了一种精确描述超短、紧聚焦激光脉冲的新方法,其思路是根据两个无量纲小量ε=1/(ω0t0)和s=1/(k0w0)（其中ω0=ck0为中心振荡频率,t0为脉冲延迟时间,w0为激光束腰半径）进行展开来计算脉冲的高阶修正场.在激光束近轴近似表达式的基础上,给出了高斯脉冲一阶修正场的解析表达式,并研究发现其振幅和相位相对于零阶修正场（即长脉冲近似）的修正量都在ε的量级甚至更小.另外对电子在超短高斯脉冲一阶修正场中的动力学特性研究发现：对于ω0t0>20的情况,零阶修正场可以正确地描述电子被光场加速的特性;当ω0t0<20时,则需要采用高阶修正场.关键词：超短激光脉冲激光加速 相似文献
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温稠密物质的物性参数在惯性约束聚变能源、Z箍缩等高能量密度物理领域的实验结果分析和物理过程数值模拟等方面有着重要的应用价值.本文应用部分电离等离子体模型,在理想自由能的基础上考虑了库仑相互作用、排斥体积作用和极化作用等非理想特性,开展了温稠密等离子体物态方程和电离平衡的研究.计算了温稠密铝等离子体的压强等物态方程数据和在密度为1.0×10^-4-3.0 g/cm^3,温度为1.0×10^4-3.0×10^4 K范围内的粒子组分.计算结果显示,铝等离子体的平均电离度在临界密度区域内随着密度的增加而突然增大.根据非理想Saha方程中有效电离能这一关键参数,分析了铝等离子体平均电离度在临界密度区域内随密度迅速增大的现象. 相似文献
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1 Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｔｈｅｍｅｔｈｏｄｓｔｈａｔｃａｎｍｅａｓｕｒｅｔｈｅｐｈａｓｅａｎｄｔｈｅ ｐｕｌｓｅｄｕｒａｔｉｏｎｍａｉｎｌｙｉｎｃｌｕｄｅｔｈｅＦＲＯＧ[1] (ｆｒｅｑｕｅｎｃｙ -ｒｅｓｏｌｖｅｄｏｐｔｉｃａｌｇａｔｉｎｇ)ａｎｄｔｈｅＳＰＩＤＥＲ[2 ] (ｓｐｅｃｔｒａｌ ｐｈａｓｅｉｎｔｅｒｆｅｒｏｍｅｔｒｙｆｏｒｄｉｒｅｃｔｅｌｅｃｔｒｉｃ ｆｉｅｌｄｒｅｃｏｎｓｔｒｕｃｔｉｏｎ) .ＦＲＯＧ[1] ｕｓｅｓｔｈｅｕｎｋｎｏｗｎｐｕｌｓｅｉｔｓｅｌｆａｓａｔｉｍｅ ｄｅｌａｙｅｄ ｇａ… 相似文献
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To measure the characteristics of ultrashort laser pulse, an apparatus design and its data processing based on SPIDER are put forward. In this method, the data processing is very simple and only basic mathematic calculation is needed. Furthermore, the pulse to be measured is avoided to pass through any dispersive structure before it arrives at the nonlinear crystal in the designed apparatus. In such a design, the pulse duration less than 10fs can be measured precisely. 相似文献
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回顾了短暂时间间隔测量的历史。条纹概念的引入、电光源和电子仪器的使用、激光的出现使能测量到的短暂时间间隔大大缩短。由于对撞脉冲锁模和啁啾脉冲压缩新概念的提出,人们将脉冲宽度压缩到了几个飞秒。介绍了自锁模钛宝石激光器的锁模、放大和调谐的工作原理以及飞秒技术在物理学、生物学、化学控制反应、光通讯等领域中的应用。 相似文献
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Naeem A. Tahir Paul Neumayer Alexander Shutov Antonio R. Piriz Igor V. Lomonosov Vincent Bagnoud Sofia A. Piriz Claude Deutsch 《等离子体物理论文集》2019,59(4-5)
This paper describes an experiment design based on numerical simulations to measure the equation‐of‐state properties of high‐energy‐density (HED) matter using intense particle beams. The simulations are performed using a 2D hydrodynamic computer code, BIG2, while the beam parameters are considered to match the Facility for Antiprotons and Ion Research beam. This study has shown that in such experiments one can generate different phases of HED lead. Similar calculations are planned for other materials. 相似文献
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类锂硅离子软X射线激光研究 总被引：1，自引：0，他引：1
在激光等离子体典型参数条件下，利用碰撞－辐模型计算了类锂硅离子５ｆ－３ｄ和４ｆ－３ｄ跃的粒子数反转比率和激光增益系数。讨论了不同热带条件和不同冷却速度下，激光增益系统数的变化。计算结果表明，高功率，短脉冲激光生产的高温等离子体在快速冷却条件下能产生软Ｘ射的线激光增益。 相似文献
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研究了均匀等离子体中超短脉冲激光在传输过程中的脉宽、峰值功率随时间，空间变化的解析式，结果表明，对于２５ｆｓ左右的超短脉冲，由等离体色散引起的脉宽变长及峰值功率降低效应是明显的。 相似文献
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A linear theory on the propagation of ultrashort pulses including only a few cycles in underdense plasmas is presented. It is shown that the dispersion in plasmas causes severe distortions in the pulse shape, including pulse chirping and spreading. The analytical calculations coincide very well with those obtained by particle-in-cell (PIC) simulations. The upper limit of the peak amplitude of the pulses, above which the linear theory breaks down due to the setting in of nonlinear effects of both the relativistic electron-mass increase and ponderomotive force, is also examined by PIC simulations. At certain high amplitudes, it is found that the ultrashort laser pulses can propagate like solitons. 相似文献
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The uniform electron gas (UEG) is one of the key models for the understanding of warm dense matter—an exotic, highly compressed state of matter between solid and plasma phases. The difficulty in modelling the UEG arises from the need to simultaneously account for Coulomb correlations, quantum effects, and exchange effects, as well as finite temperature. The most accurate results so far were obtained from quantum Monte Carlo (QMC) simulations with a variety of representations. However, QMC for electrons is hampered by the fermion sign problem. Here, we present results from a novel fermionic propagator path integral Monte Carlo in the restricted grand canonical ensemble. The ab initio simulation results for the spin-resolved pair distribution functions and static structure factor are reported for two isotherms (T in the units of the Fermi temperature). Furthermore, we combine the results from the linear response theory in the Singwi-Tosi-Land-Sjölander scheme with the QMC data to remove finite-size errors in the interaction energy. We present a new corrected parametrization for the interaction energy and the exchange–correlation free energy in the thermodynamic limit, and benchmark our results against the restricted path integral Monte Carlo by Brown et al. [Phys. Rev. Lett. 110 , 146405 (2013)] and configuration path integral Monte Carlo/permutation-blocking path integral Monte Carlo by Dornheim et al. [Phys. Rev. Lett. 117 , 115701 (2016)]. 相似文献
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LI Xuexin LIU Yaqing ZHAI KanXU Zhizhan HAN Shensheng 《Chinese Journal of Lasers》1997,6(6):539-542
ＥｆｅｃｔｓｏｆＰｕｌｓｅＤｕｒａｔｉｏｎｓｏｎＨｉｇｈｏｒｄｅｒＨａｒｍｏｎｉｃＧｅｎｅｒａｔｉｏｎＬＩＸｕｅｘｉｎＬＩＵＹａｑｉｎｇＺＨＡＩＫａｎＸＵＺｈｉｚｈａｎＨＡＮＳｈｅｎｓｈｅｎｇ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＯｐｔｉｃｓａｎ... 相似文献