由激光在等离子体中激发的尾波场产生的超强太赫兹电磁辐射

在不均匀等离子体中产生的激光尾波场在一定条件下可以通过线性模式转换产生电磁辐射。由于激光尾波场可以达到的电场振幅达100Gv/m，其振动频率在太赫兹（1012Hz）附近，用这种方法可以产生超强GV/m的太赫兹辐射。它既可以作为一种辐射源，也可以在新型等离子体波加速器中用以诊断等离子体波的振幅。     

相对论效应对强激光在非均匀等离子体介质中吸收的影响

随着激光新技术的发展,超短脉冲强激光打靶成为目前激光等离子体领域的一个新动向。超短脉冲打靶能产生超短scale-lensth的表面等离子体层,激光在这样的等离子体层中的吸收问题又引起人们新的研究兴趣。对于斜入射p偏振(E矢量平行入射面)激光,存在两种吸收机制,一种是普通的碰撞阻尼引起的吸收,另一种是由于临界面附近电     

Single-Shot Broad Bandwidth Terahertz Pulse Measurement

A new method based on a chirped optical pulse interferogram has been proposed to measure terahertz radiation. The frequency domain phase information of the interferogram is used to extract the time-domain terahertz pulse waveform. In principle, the resolution of our method can be as high as the unchirped probe pulse duration, with the advantages of relatively simple measurement setup and signal extracting techniques.     

低杂波驱动电流对撕裂模不稳定性的影响

用动力论和磁流体两个途径研究了低杂波驱动电流(LHCD)对撕裂模不稳定性的影响。线性动力论的结果表明:在碰撞区,由低杂波驱动出的快电子对撕裂模扰动的响应,导致了撕裂模的增长率和扰动层宽度的减小。从对托卡马克条件下低杂波驱动电流的数值模拟及解磁流体撕裂模方程可得出,低杂波驱动电流引起电流分布的变化并使有理面移动,从而导致撕裂模的△＇值的变化。在多数情况下,撕裂模会因低杂波驱动电流而被抑制。但在文中所示的参数下,低杂波驱动电流在较高q_α值的等离子体中对撕裂模起增稳作用;而在较低q_α值的等离子体中有失稳作用。这一结果与实验观测结果定性相符。     

飞秒强激光产生沿靶表面出射高能超热电子束

在超短超强激光与固体薄膜靶相互作用研究中,实验上首次观测到了沿靶面方向发射的高能超热电子束.该电子束只有在等离子体电子密度标长较短的条件下才会出现.理论模拟表明,靶表面电磁场的约束作用是产生此电子束的主要原因.这一结果有助于加深对激光愤性约束聚变快点火实验中的锥靶物理过程的理解,并有潜在的应用前景.     

Transmission Degradation of Femtosecond Laser Pulses in Opened Cone Targets

Irradiated by femtosecond laser pulses with different energies, opened cone targets behave very differently in the transmission of incident laser pulses. The targets, each with an opening angle of 71 and an opening of 5 μm, are fabricated using standard semiconductor technology. When the incident laser energy is low and no pre-plasma is generated on the side walls of the cones, the cone target acts like an optical device to reflect the laser pulse, and 15% of the laser energy can be transmitted through the cones. In contrast, when the incident laser energy is high enough to generate pre-plasmas by the pre-pulse of the main pulse that fills the inner cone, the cone with the plasmas will block the transmission of the laser, which leads to a decrease in laser transmission compared with the low-energy case with no plasma. Simulation results using optical software in the low-energy case, and using the particle-in-cell code in the high-energy case, are primarily in agreement with the experimental results.     

Electromagnetic Emission from Laser Wakefields in Magnetized Underdense Plasmas

A wakefield driven by a short intense laser pulse in a perpendicularly magnetized underdense plasma is studied analytically and numerically for both weakly relativistic and highly relativistic situations.Owing to the DC magnetic field,a transverse component of the electric fields associated with the wakefield appears,while the longitudinal wave is not greatly affected by the magnetic field up to 22 Tesla.Moreover,the scaling law of the transverse field versus the longitudinal field is derived.One-dimensional particle-in-cell simulation results confirm the analytical results.Wakefield transmission through the plasma-vacuum boundary,where electro-magnetic emission into vacuum occurs,is also investigated numerically.These results are useful for the generation of terahertz radiation and the diagnosis of laser wakefields.     

Critical Initial Amplitude of Langmuir Wave Damping

By one-dimensional Vlasov-Poisson simulation,the critical initial state marking the transition between the Landau scenario,in which the electric fields definitively damped to zero and the O’NEIL scenario,in which the Landau damping is stopped after a certain damping stage,is studied.It is found that the critical initial amplitude ε can only exist when the product of the wave number(k m) and the electron thermal velocity(v th) is moderate,that is,0.2 < k m v th < 0.7.Otherwise,no critical initial amplitude is found.The value ε increases with the increase in k m for a fixed v th,and also increases with the increase in v th for a fixed k m.When k m v th is fixed,the value ε also changes with the wave number and the electron thermal velocity,even though the damping rate and the oscillation frequency are the same in this case.     

激光诱导击穿光谱在液体样品分析中的应用

介绍了激光诱导击穿光谱(LIBS)技术的原理,重点讨论了该技术在液体样品方面的技术发展和应用,分析并比较了选取不同样品形式(液体内部、液体表面、液体喷流、液滴以及将液体转化为固体等)的优劣,指出提高元素检测限的关键。液体LIBS技术因其可在线、快速检测等优点,在环境检测、污水处理、生物医药、工业控制等诸多方面具有巨大的应用潜力。