圆柱形等离子体对微波散射的数值模拟与实验研究

模拟和实验研究了非均匀圆柱形等离子体及阵列对微波的散射作用。利用有限时域差分(FDTD)方法仿真得到了等离子体柱的密度、碰撞频率对微波传播系数的影响,并利用低气压放电产生的等离子体柱对微波的吸收和散射作用进行了验证。结果表明:电子密度中心高、周围低的非均匀等离子体柱可将微波散射至两个侧向;等离子体频率越大,散射的微波功率越强;增加碰撞频率使等离子体柱的微波散射功率减小、吸收增大。等离子体必须具有合适的密度,才能对微波反射产生较大影响。     

ECR微波等离子体离子输运的数值模拟

建立了ECR微波等离子体源离子输运的平板和圆柱模型,对离子历经的空间区域的输运过程进行了数值研究。采用Monte Carlo(M-C)方法模拟了存在外磁场情况下,离子离开开放电室后历经中性区、鞘层区、最后被加负偏压的工作表面吸收的全过程,考虑了离子与中性粒子的电荷交换碰撞玫弱性散性,统一处理了中性区和鞘层区电势的衔接,采用曲线拟合,电势自洽迭代方法把中性区和鞘层区衔接起来,得到了光滑自治的电势分布曲线和鞘层区不同位置处的速度分布、能量分布及角分布。     

压缩空气微波等离子体发射光谱的实验研究

利用微波等离子体发生装置,以压缩空气为工作气体,在1～5 atm气压下激发了微波等离子体。使用光谱测量系统,对不同气压和不同入射微波功率情况下的压缩空气微波等离子体的发射光谱进行了实验研究。结果显示,在其他条件不变时,随着气压升高,压缩空气微波等离子体的带状连续谱特征逐渐减弱;随着入射微波功率降低,带状连续谱强度逐渐减弱而带状连续谱特征依然显著。实验结果为了解压缩空气微波等离子体的光谱特性和NO活性基团的产生条件提供了实验依据。     

激光等离子体中相干Thomson散射的实验研究

在“星光II”装置上进行了相干Thomson散射实验。实验中以0.35μm激光为作用束,以0.53μm激光作为探针光束,散射光采用反射式收光系统配光谱仪、条纹相机和CCD记录,得到较高时间和空间分辨散射光谱,分析得出时间变化的激光等离子体参数和ui。     

常压微波等离子体射流实验装置

介绍了使用2.45GHZ微波源激励产生常压等离子体射流（MPJ）的装置,该装置结构简单,使用可靠,实验内容丰富,适合教学要求。     

汤姆孙散射：等离子体参数诊断的强大工具

汤姆孙散射是低能光子与自由电子之间的弹性散射.因为汤姆孙散射光谱携带着等离子体涨落的信息,通过测量汤姆孙散射光谱可以高精度地测量等离子体的多种参数,如电子温度、电子密度、等离子体流速等等.经过多年的发展,汤姆孙散射已经成为等离子体物理研究中最重要的一种诊断工具.     

汤姆孙散射：等离子体参数诊断的强大工具

汤姆孙散射是低能光子与自由电子之间的弹性散射.因为汤姆孙散射光谱携带着等离子体涨落的信息,通过测量汤姆孙散射光谱可以高精度地测量等离子体的多种参数,如电子温度、电子密度、等离子体流速等等.经过多年的发展,汤姆孙散射已经成为等离子体物理研究中最重要的一种诊断工具.     

大气中固体燃烧等离子体与微波相互作用的实验研究

设计制造了含特定组分的化学药剂,利用热力学方法对其在大气中燃烧所产生的等离子体的电子密度进行了理论计算,对该等离子体对2~15 GHz波段微波的透射衰减和反射进行了测试。测试结果表明,该等离子体对该波段微波具有宽波段强吸收和弱反射性能,波段内的平均吸收大于25 dB,反射信号几乎淹没在背景噪声中。并从理论上分析了带电子与中性粒子的造成这一现象的主要原因是碰撞吸收。     

高功率微波与大气等离子体相互作用研究

研究了高功率微波持续击穿大气产生等离子体的演化过程,给出了微波干扰给定等离子体形成黑障效应的结果。     

Laser-beam smoothing induced by stimulated brillouin scattering in an inhomogeneous plasma

We present results of two-dimensional simulations of the stimulated Brillouin scattering (SBS) of an optically smoothed laser beam propagating in an expanding plasma. In the weak damping limit, both backscattered and transmitted light waves exhibit an additional spatiotemporal incoherence, which is shown to be induced by SBS taking place in an inhomogeneous plasma. This mechanism is not related to laser-beam self-focusing and is thus complementary to plasma-induced smoothing [A. J. Schmitt and B. B. Afeyan, Phys. Plasmas 5, 503 (1998)]. The incoherence induced by SBS in the entrance part of the plasma could reduce the growth of parametric instabilities developing further inside the plasma and is able to significantly enlarge the spreading angle of the transmitted light. The angular width of the backscattered light is also found to be significantly larger than the aperture angle of the incident beam.     

Analysis of Landau damping in radially inhomogeneous plasma column

The Landau damping behavior in a cylindrical inhomogeneous warm magnetized plasma waveguide has been studied.The radial inhomogeneity for different characteristic lengths(L0) with strong spatial dispersion has been taken into account.The analyses have been considered for two limits ωce ωpe and ωce ωpe. Due to the radial inhomogeneity of the plasma, all essential equations for studying the Landau damping are calculated in the Bessel–Furrier and differential Bessel–Furrier expansions. The dependence of Landau damping on the inhomogeneity, temperature and external magnetic field for electrostatic modes is scrutinized and described in detail through numerical calculations. The associated numerical results are presented and discussed.     

Stimulated scattering and wavefront conjugation in an inhomogeneous plasma

In the context of the problem of stimulated scattering we discuss the mechanism of wavefront conjugation in an inhomogeneous plasma proposed relatively recently, associated with a difference in suppression of scattering (due to inhomogeneities) for the inverted and uninverted components. We analyze the solutions of the integro-differential equations describing this process both numerically and analytically for different sound attenuation lengths (v ⁻¹). It is shown that for this effect to exist it is necessary that n not be too small. We also consider extinction of the inverted wave in terms of this mechanism. Zh. éksp. Teor. Fiz. 113, 168–180 (January 1998)     

Interferometry of hyper-Rayleigh scattering by inhomogeneous thin films

The use of specific symmetry properties of optical second-harmonic generation (the s, s-exclusion rule) has allowed us to observe high-contrast hyper-Rayleigh interference patterns in completely diffuse light, an effect that has no analog in the case of linear (Rayleigh) scattering.     

Effective dichroism in forward scattering by inhomogeneous birefringent medium

The Mueller matrix model for inhomogeneous medium characterized by simultaneous linear and circular birefringence for single scattering in the forward direction is derived. We find that the presence of inhomogeneity results in the occurrence of new polarization effects. In particular, forward scattering by inhomogeneous birefringent medium exhibits linear and circular dichroism. We show that in the case of weak depolarization (when Cloude's entropy is less than 0.5), the initial parameters for linear and circular birefringence can be obtained from deterministic Mueller matrix associated with the largest eigenvalue of Cloude's coherency matrix. Sample calculations are given for quartz.     

Compression of ultraintense laser pulses in inhomogeneous plasma upon backward stimulated raman scattering

The potential for time compression of ultraintense laser pulses in plasma based on nonlinear interactions between waves during backward stimulated Raman scattering is analyzed analytically and numerically. The optimal conditions for obtaining a maximal energy conversion coefficient of 10-ps laser pulses to the energy of 100-fs Stokes pulses are found.     

Alfven-wave scattering in inhomogeneous media

Alfven-wave scattering by inhomogeneities of the permittivity tensor (r) is examined. The scattering index , phase velocity v*, and group velocity c* are calculated over the entire wavelength range. Asymptotic formulas for , v*, and c* are derived for long (as compared with scatterer size), short, and ultrashort wavelengths.Moscow Institute of Electronic Engineering. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 5, pp. 421–432, May, 1992.