非圆截面环流器等离子体对于高n理想磁流体气球模的最佳压强分布

本文假定等离子体局部压强梯度由理想磁流体高n气球模所限定,讨论了非圆截面环流器的最佳压强剖面。分析了椭圆及三角变形的效应,发现三角变形对提高稳定性很有利;q剖面对平均比压值及中心比压值都有强烈影响,而沿半径下降的q剖面对提高比压值很有利。     

Dust Charging in the Sheath of an Electronegative Plasma

We theoretically investigate the dust charging in the sheath of an electronegative plasma, by using a single dust grain model based on a previous sheath structure [Chin. Phys. Lett 20 (2003) 1537] in which cold positive ions and hot negative ions have been assumed. It is found that dust grains are first charged negatively at the sheath     

Two-dimensional numerical research on effects of titanium target bombarded by TEMPⅡ accelerator

Two-dimensional numerical research has been carried out on the ablation effects of titanium target irradiated by intense pulsed ion beam （IPIB） generated by TEMP Ⅱ accelerator. Temporal and spatial evolution of the ablation process of the target during a pulse time has been simulated. We have come to the conclusion that the melting and evaporating process begin from the surface and the target is ablated layer by layer when the target is irradiated by the IPIB. Meanwhile, we also obtained the result that the average ablation velocity in target central region is about 10 m/s, which is far less than the ejection velocity of the plume plasma formed by irradiation. Different effects have been compared to the different ratio of the ions and different energy density of IPIB while the target is irradiated by pulsed beams.     

强流脉冲离子束辐照靶材烧蚀效应二维数值研究

对强流脉冲离子束(IPIB)辐照Ti靶的烧蚀效应进行了二维数值研究.得到了表面烧蚀物质随脉冲时间的变化关系.得出TEMP Ⅱ 型加速器产生的脉冲束流辐照靶材时引起的汽、液化均是从表面开始、并且汽化过程中表面物质被层层烧蚀的结论.同时，得到中心区的平均烧蚀速度为10m/s 数量级，它远小于产生的烧蚀等离子体的喷发速度.得到脉冲期间靶材内部不同位置烧蚀斑痕形状的时间演化过程，以及束流中含有的离子种类分额不同时IPIB辐照过程产生的不同效果. 关键词： 强流脉冲离子束 靶 烧蚀过程 二维数值模拟     

强流脉冲离子束辐照靶及其喷发的数值研究

利用拟合实测的TEMP Ⅱ型加速器磁绝缘二极管(MID)电压波形及其焦点附近束流密度曲线，建立了Gaussian分布模型，据此计算了与靶作用的离子的能量及数量，采用Monte Carlo(MC)方法计算了沉积在靶内的能量.并以此作为热源，与流体动力学(HD)模型相结合，对不同的靶状态采用相应的状态方程，模拟计算了靶内压力演化情况; 同时对烧蚀产生的等离子体采用理想气体状态方程, 结合HD方程组, 模拟计算了喷发过程中压力的空间演化过程. 关键词： 强流脉冲离子束 Gaussian模型 HD方程 数值研究     

强流脉冲离子束烧蚀等离子体向背景气体中喷发的数值研究

强流脉冲离子束辐照靶材产生烧蚀等离子体向背景气体中传播与向真空中传播不同，包括喷发等离子体与背景气体的相互作用.本文建立了该过程的二维气体动力学模型，计算了等离子体向压强范围从10^-6大气压到大气压背景气体中传播时的情况.结果表明，背景气体压强不同时，等离子体传播的现象也不相同.向真空中可以自由膨胀，向大气压中膨胀受限；当背景气压在千分之一大气压左右时，等离子体在背景气体中形成“雪犁”状，羽状等离子体出现快速和慢速传播分离现象.     

Impurity-induced local modes in one-dimensional dusty plasma chains

The effects of impurity on eigenmodes in one-dimensional dusty plasma lattices are studied.It is found that local modes can be excited besides lattice waves,due to the existence of an impurity particle.The dispersion relations of the modes are derived accordingly.Properties of the lattice and local modes are also analyzed and discussed,particularly for their symmetric features and conditions of the mode excitation.     

Propagation of Plasma Generated by Intense Pulsed Ion Beam Irradiation

Taking the calculation results based on the established two-dimensional ablation model of the intense-pulsed-ionbeam （IPIB） irradiation process as initial conditions, we build a two-dimensional hydrodynamic ejection model of plasma produced by an IPIB-irradiated metal titanium target into ambient gas. We obtain the conclusions that shock waves generate when the background pressure is around 133 mTorr and also obtain the plume splitting phenomenon that has been observed in the experiments.     

Dust Charging in Electronegative SiH4 Plasmas

We theoretically investigate the dust charging in electronegative silane (SiH4) plasmas, taking into account the effects of UV photodetachment. It is found that UV photodetachment could significantly lower the dust negative charge and even makes dust grains be positively charged under some special conditions. In addition, the other parameters, involving the negative ion and dust number densities, electron temperature and dust radius, have great effects upon the dust charging.     

A Two-Flux Radiation Model for Helical Instability of Arcs

A two-flux radiation model of the helical instability of arcs in axial magnetic field is presented. The temperature (and electrical conductivity) is approximated in a more realistic way (parabolic instead of flat profile) and a simplified term of radiation losses is included in the energy equation. The magnetohydrodynamic equations in an electrostatic approximation serve as the starting point of the theorv. Using a linear time-dependent perturbation theory, the corresponding equations and an explicit analytic expression that corresponds to the term of radiation losses are derived in the presence of the radiation transfer energy, from which the marginal Maecker number and the growth rate of the helical instability can be given. It is found that, in comparison with the results without radiation, the arc stable area is reduced.