多光子非线性Compton散射对等离子体平面反射电磁波的影响

应用多光子非线性Compton散射模型和电磁波与等离子体相互作用模型,研究了Compton散射对等离子体平面反射电磁波特性的影响,提出了将Compton散射作为影响等离子体平面反射电磁波的机制,给出了等离子体平面反射电磁波反射率的修正方程,并进行了仿真实验。结果表明：不同频率下,低频段等离子体密度随电场强度增大而迅速增大,到达平衡态时间明显缩短,这是因散射使场强迅速增大,等离子体中粒子发生电离几率增大的缘故。高频入射波使反射波强度减低最多,最后几乎趋于0,这是因散射使等离子体频率高于入射波频率的成分大大增加的缘故。不同频率入射波的反射波频率有微小增大,这是因散射使信号与等离子体复合扩散时间尺度差距缩小,反射波的非线性效应逐步显现的缘故。随碰撞频率增大,低密度等离子体密度增加最快,到达平衡态时间最短,这是因散射使等离子体碰撞频率增大,有更多粒子参与电离的缘故。     

Compton散射对激光等离子体通道天线特性的影响

应用多光子非线性Compton散射模型和数值计算方法,研究了激光等离子体通道天线传播和辐射特性,结果表明:随通道周围介质损耗和传输模式阶数的增大,传输模式THnm衰减常数明显增大.这是因散射使通道内外电场和磁场增强,粒子间碰撞频率增大,电场使更多分子电离而吸收更多能量的缘故.随模式阶数增大,电性有耗介质使相移常数明显减小.这是因散射使高阶模式可能存在被耦合电场俘获的缘故.等离子体耦合频率为0.7附近,衰减常数随频率增大而剧烈增大.这是因散射使介质分子发生二、三阶电离,更多电子被耦合电场急剧加速的缘故.随天线长度增加,天线辐射方向图主瓣和副瓣数量、宽度和最大辐射方向发生明显变化.这是因散射使天线频率增大,辐射波长变短,粒子电离几率增大,辐射波能量和频率成分增大的缘故.     

Compton散射对激光等离子体通道天线特性的影响

应用多光子非线性Compton散射模型和数值计算方法, 研究了激光等离子体通道天线传播和辐射特性,结果表明: 随通道周围介质损耗和传输模式阶数的增大, 传输模式TH n m衰减常数明显增大。这是因散射使通道内外电场和磁场增强, 粒子间碰撞频率增大, 电场使更多分子电离而吸收更多能量的缘故。随模式阶数增大, 电性有耗介质使相移常数明显减小。这是因散射使高阶模式可能存在被耦合电场俘获的缘故。等离子体耦合频率为0.7附近, 衰减常数随频率增大而剧烈增大。这是因散射使介质分子发生二、三阶电离, 更多电子被耦合电场急剧加速的缘故。随天线长度增加, 天线辐射方向图主瓣和副瓣数量、宽度和最大辐射方向发生明显变化, 这是因散射使天线频率增大, 辐射波长变短,粒子电离几率增大, 辐射波能量和频率成分增大的缘故。     

Compton散射下离子初始速度对等离子体鞘层厚度的影响

应用相对论理论、Compton散射等离子体离子源和龙格-库塔方法,研究了Compton散射对等离子体鞘层厚度的影响,提出了Compton散射等离子体离子源概念,并将入射光和Compton散射光作为形成等离子体离子初始速度的新机制,给出了Compton散射下鞘层空间内电位梯度随等离子体离子初始速度变化的修正方程,并进行了数值模拟.结果表明,与Compton散射前相比,Compton散射使等离子体鞘层厚度随加速电压增大而明显的非线性增大,这主要是由于Compton散射使离子与电子碰撞频率增大,电子温度升高,使离子初始速度和能量增大的缘故.     

超强激光照射三维时变等离子体散射新机制

应用多光子非线性Compton散射模型和电流密度拉普拉斯变换改进的时域有限差分法,研究了超强激光照射三维时变等离子体的散射特性,提出了Compton散射光是影响等离子体散射的新机制,给出了该等离子体散射截面和频率随时间变化的修正方程,并进行了数值仿真。结果表明：与Compton散射前相比,Compton散射使等离子体散射截面增大,且随频率增大迅速衰减。这是因散射使等离子体中电子从耦合激光场中获得更多能量,从而导致电子被耦合场俘获的缘故;使瞬变等离子体最大频率随时间呈准直线缓慢下降趋势。这是因散射使等离子体中电子辐射阻尼效应增强,从而导致电子能量衰减、频率下降的缘故;使缓变等离子体频率随时间缓慢增大。这是因散射使等离子体中电子辐射阻尼增大效应减弱了频率增大的缘故。     

超强激光照射三维时变等离子体散射新机制

应用多光子非线性Compton散射模型和电流密度拉普拉斯变换改进的时域有限差分法,研究了超强激光照射三维时变等离子体的散射特性,提出了Compton散射光是影响等离子体散射的新机制,给出了该等离子体散射截面和频率随时间变化的修正方程,并进行了数值仿真。结果表明：与Compton散射前相比,Compton散射使等离子体散射截面增大,且随频率增大迅速衰减。这是因散射使等离子体中电子从耦合激光场中获得更多能量,从而导致电子被耦合场俘获的缘故;使瞬变等离子体最大频率随时间呈准直线缓慢下降趋势。这是因散射使等离子体中电子辐射阻尼效应增强,从而导致电子能量衰减、频率下降的缘故;使缓变等离子体频率随时间缓慢增大。这是因散射使等离子体中电子辐射阻尼增大效应减弱了频率增大的缘故。     

Compton散射下离子初始速度对等离子体鞘层厚度的影响

应用相对论理论、Compton散射等离子体离子源和龙格-库塔方法,研究了Compton散射对等离子体鞘层厚度的影响,提出了Compton散射等离子体离子源概念,并将入射光和Compton散射光作为形成等离子体离子初始速度的新机制,给出了Compton散射下鞘层空间内电位梯度随等离子体离子初始速度变化的修正方程,并进行了数值模拟。结果表明,与Compton散射前相比,Compton散射使等离子体鞘层厚度随加速电压增大而明显的非线性增大,这主要是由于Compton散射使离子与电子碰撞频率增大,电子温度升高,使离子初始速度和能量增大的缘故。     

Compton散射对等离子体零色散附近调制不稳定性的影响

应用Compton散射模型和非线性Schrdinger方程,研究了Compton散射对等离子体零色散附近调制不稳定性的影响,提出了将Compton散射作为形成调制不稳定性的新机制,给出了等离子体修正色散方程,并进行了数值计算.结果表明:二阶色散较大时,远离零色散附近调制不稳定性增益谱由入射和散射光产生的二阶色散决定,随二阶色散增大,四阶色散作用迅速减小,这是因散射效应有效削弱了四阶效应的缘故.零色散附近调制不稳定性增益谱由入射和散射光产生的四阶色散决定,二阶色散被湮灭,微扰频率最大值向临界微扰频率较快靠近,这是因散射效应有效增强了四阶效应的缘故.增益谱宽随等离子体损耗增大而迅速增大,这是因功率增大使散射效应增强,导致带电粒子辐射阻尼增强的缘故.     

Compton散射下太赫兹波段介质微腔光学特性

应用Compton散射模型、1维等离子体光子晶体模型和数值计算方法,研究太赫兹波段介质微腔光学特性,给出了系统反射率、反射相移和相位穿透深度修正方程和实验验证。结果表明：与散射前相比,系统中心波长左移15 ,这是因散射使等离子体层中电子与光子碰撞频率增大效应导致系统振荡频率增大的缘故;反射相移在截止区与波长呈准线性关系,中心波长处相对 有一定偏离,这是因散射使等离子体层中电子辐射阻尼增强效应导致系统振荡频率减小的缘故;禁带区相位穿透深度增大,这是因散射与入射光形成的耦合光与入射光在禁带区的相位不同,导致入射光禁带对于耦合光产生局部失效的缘故。谐振峰左移15 ,强度提高了22倍,这是因散射产生的等离子体频率和电子辐射阻尼增大效应使系统中心波长左移,透射几率增大,从而导致透射禁带两个谐振峰左移和谐振峰强度提高的缘故。     

Compton散射下太赫兹波段介质微腔光学特性

应用Compton散射模型、1维等离子体光子晶体模型和数值计算方法，研究太赫兹波段介质微腔光学特性，给出了系统反射率、反射相移和相位穿透深度修正方程和实验验证。结果表明：与散射前相比，系统中心波长左移15 ，这是因散射使等离子体层中电子与光子碰撞频率增大效应导致系统振荡频率增大的缘故；反射相移在截止区与波长呈准线性关系，中心波长处相对 有一定偏离，这是因散射使等离子体层中电子辐射阻尼增强效应导致系统振荡频率减小的缘故；禁带区相位穿透深度增大，这是因散射与入射光形成的耦合光与入射光在禁带区的相位不同，导致入射光禁带对于耦合光产生局部失效的缘故。谐振峰左移15 ，强度提高了22倍，这是因散射产生的等离子体频率和电子辐射阻尼增大效应使系统中心波长左移，透射几率增大，从而导致透射禁带两个谐振峰左移和谐振峰强度提高的缘故。     

Different configurations of transferred atmospheric pressure plasma jet and their application to polymer treatment

The employment of atmospheric pressure plasma jets (APPJs) in a large sort of applications is limited by the adversities related to the size of the treated area and the difficulty to reach the target. The use of devices that employ long tubes in their structure has contributed significantly to overcome these challenges. In this work, two different plasma systems employing the jet transfer technique are compared. The main difference between the two devices is how the long plastic tube was assembled. The first one uses a copper wire placed inside a long plastic tube. The other device has a metallic mesh installed in a concentric arrangement between two coaxial plastic tubes. As a result, the two APPJ systems exhibit different properties, with the wire assembly being more powerful, also presenting higher values for the electrical current and rotational temperature when compared to the mesh mounting. X-ray photoelectron spectroscopy (XPS) demonstrates that both configurations were capable of inserting O-containing functional groups on the polypropylene (PP) surface. However, the transferred plasma jet with wire assembly was able to add more functional groups on the PP surface. The results from XPS analysis were corroborated with water contact angle measurements (WCA), being that lower WCA values were obtained when the PP surface presented higher amounts of O-containing groups. Furthermore, the results suggest that the APPJ with wire configuration is more appropriate for material treatments, while the transferred jet with mesh arrangement tends to present lower electrical current values, being more suitable for biological applications.     

Enhanced laser-induced plasma channels in air

Plasma is a significant medium in high-energy density physics since it can hardly be damaged. For some applications such as plasma based backward Raman amplification(BRA), uniform high-density and large-scale plasma channels are required. In the previous experiment, the plasma transverse diameter and density are 50–200 μm and 1–2 × 10~(19)cm~(-3),here we enhance them to 0.8 mm and 8 × 10~(19)cm~(-3), respectively. Moreover, the gradient plasma is investigated in our experiment. A proper plasma gradient can be obtained with suitable pulse energy and delay. The experimental results are useful for plasma physics and nonlinear optics.     

外加磁场微波等离子推力器内流场数值模拟

为了提高微波等离子推力器性能，改善等离子体对电磁波能量的吸收状况，提高核心区温度，提出外加磁场的方案，并对热等离子体进行了数值模拟.假设局域热平衡条件，采用Navier-Stokes，Maxwell和Saha方程，利用压力修正的半隐格式和时域有限差分求解方法，建立了径向磁镜场下推力器内等离子体流场的数值计算模型.数值模拟结果表明：外加磁场后的磁感应强度小于0.5 T时，推力器内热等离子体核心区最高温度随磁感应强度的增加而迅速提高.外加磁场后的磁感应强度大于0.5 T时，核心区最高温度随磁感应强度的增加而缓慢提高.磁感应强度为0.5 T时，热等离子体核心区最高温度与不加磁场相比提高了24%.外加磁场对等离子体流场速度分布影响不大. 关键词： 等离子体模拟 等离子体相互作用 等离子体流动     

The dielectric tensor and field equations in the inhomogeneous cold collisionless magnetized drift plasmas with elliptical cross sections

In this Letter the dielectric permittivity tensor and field equations in multi layer cold collisionless magnetized inhomogeneous drift plasma columns with confocal elliptical cross sections are investigated. It will be shown that the dielectric tensor of each region can be written as non-operational Hermitian and pure spatial operational parts.     

强光一号POS等离子体源性能参数测量

以强光一号等离子体源（电缆枪）为研究对象,采用电荷收集器（法拉第杯）对强光一号等离子体源性能参数进行测量。实验结果表明:等离子体发射密度与电缆等离子体枪枪芯到枪口的距离正相关,而发射速度与电缆等离子体枪枪芯到枪口的距离负相关;增大电缆枪驱动电压时,等离子体发射密度增速远小于驱动电流增速。重复性研究表明,对由数十支电缆枪组成的等离子体源而言,单支电缆枪放电分散性对其输出等离子体整体分布均匀性影响不大。不确定度分析表明,通过多次重复实验求平均值,可以有效减小实验结果的不确定度,发射密度测量结果的合成标准不确定度在10%以内。     

Dust Sheared Flow Driven Instability of Dust Drift Waves in a Nonuniform Magnetoplasma

We investigate instability of dust drift waves in a nonuniform dusty magnetoplasma containing transverse sheared plasma flow that is produced by a nonuniform electric field. By using Boltzmann distributed electrons and ions, Poisson’s equation, as well as the dust continuity equation with perpendicular guiding center dust drift speed, we derive an eigenvalue equation, which strongly depends on the profiles of dust sheared flow and dust density gradient. The eigenvalue equation is analytically solved to obtain expressions for the growth rate and threshold of a convective instability arising from resonant interactions between the dust drift waves and sheared flows. The result may be relevant to the understanding of short wavelength (in comparison with the ion gyroradius) electrostatic fluctuations in magnetized plasmas of Saturn rings and in cometary tails. PACS numbers: 52.27.Lw; 52.35.Fp     

Studies on the Plasma Shielding of 1.06μm Laser on the Aluminum Target

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Atmospheric pressure plasma jet utilizing Ar and Ar/H_2O mixtures and its applications to bacteria inactivation

An atmospheric pressure plasma jet generated with Ar with H2O vapor is characterized and applied to inactivation of Bacillus subtilis spores. The emission spectra obtained from Ar/H2O plasma shows a higher intensity of OH radicals compared to pure argon at a specified H2O concentration. The gas temperature is estimated by comparing the simulated spectra of the OH band with experimental spectra. The excitation electron temperature is determined from the Boltzmann’s plots and Stark broadening of the hydrogen Balmer Hβline is applied to measure the electron density. The gas temperature, excitation electron temperature, and electron density of the plasma jet decrease with the increase of water vapor concentration at a fixed input voltage. The bacteria inactivation rate increases with the increase of OH generation reaching a maximum reduction at 2.6%(v/v) water vapor. Our results also show that the OH radicals generated by the Ar/H2O plasma jet only makes a limited contribution to spore inactivation and the shape change of the spores before and after plasma irradiation is discussed.     

Experimental observation of dust circulation in unmagnetized cogenerated dusty plasma

The vortex motion of a dust cloud was experimentally observed in unmagnetized cogenerated dusty plasma in different experimental parameters. Particle image velocimetry analysis demonstrated that several vortex zones exist in the dust cloud at relatively low pressures (0.06 mbar (or 6 Pa)–0.08 mbar (or 8 Pa)) and low discharge voltages (peak‐to‐peak voltage 540–560 V), whereas in relatively high pressure (0.4 mbar (or 40 Pa)–0.7 mbar (or 70 Pa)) and high discharge voltage (peak‐to‐peak voltage 690–740 V), dust vortices formed in dense dust cloud with background plasma fluctuation.     

激光等离子体光丝中太赫兹频谱的调控

研究了双色激光场激发空气成丝产生太赫兹辐射频谱的变化规律.实验观察到随驱动光功率和光丝长度增加,太赫兹光谱主要发生红移的现象.分析表明,由于等离子体密度的增加,太赫兹辐射的趋肤深度减小,等离子体吸收主导了红移的发生.在光丝足够短的条件下,趋肤深度远大于光丝长度,从而产生等离子体振荡主导的太赫兹辐射光谱蓝移.本研究为超快宽带太赫兹辐射的频谱调控提供了新思路.