等离了体源离子注入球靶的蒙特—卡罗模拟

建立了在球形靶鞘层中蒙特－卡罗模拟模型，考虑了离子与中性粒子的电荷交换碰撞和弹性散射，以及精确依赖于入射离子能量的电荷交换碰撞截面和动量输运截面。模拟了不同气压下，在鞘层扩展过程中，氮离子Ｎ＾＋２到达靶表面的能量分布和入射分布，研究了它们的变化规律。     

电子回旋共振放电的电离特性PIC/MCC模拟(Ⅰ)——物理模型与理论方法

采用粒子模拟与蒙特卡罗相结合(PIC/MCC)的方法对电子回旋共振(ECR)放电中的电离过程进行了模拟，其中带电粒子与微波的相互作用由PIC方法的电磁模型描述，粒子间的碰撞过程由MCC方法描述.考虑的碰撞类型有电子与中性粒子的弹性、激发、电离碰撞，离子与中性粒子的弹性、电荷交换碰撞，碰撞截面均依赖于能量而变化.阐述了理论分析的过程，为数值模拟ECR放电奠定了基础. 关键词： 电子回旋共振放电 粒子模拟 蒙特卡罗 电离     

气体放电空心阴极鞘层氩离子的蒙特-卡罗模拟研究

建立了气体放电空心圆筒阴极鞘层离子的自洽蒙特-卡罗模拟模型,对鞘层区内离子的输运过程进行了研究。考虑了离子与中性原子的电荷交换碰撞和弹性散射,用到了精确依赖于离子能量的电荷交换和动量输运截面。模拟了氩离子在空心阴极鞘层中的运动,得到了不同放电条件下自洽电场分布,离子的能量分布,角分布以及电子密度分布和离子密度分布。计算结果表明:离子在由鞘层边界向阴极运动过程中,离子能量分布的高能部分逐渐增大,角分布向小角度部分压缩,鞘层中的强电场对离子起加速和聚焦作用;在鞘层内离子密度分布比较均匀,只是在鞘层边界附近变化 关键词：     

气体放电阴极鞘层氩离子的自洽蒙特卡罗模拟

建立了气体放电阴极鞘层离子的自洽蒙特卡罗模拟模型,考虑了离子与中性原子的电荷交换碰撞和弹性散射,用到了精确依赖于离子能量的电荷交换和动量输运截面。模拟了氩离子在阴极鞘层中的运动,得到了不同气压下自治电场分布,离子的能量分布和角分布,发现:离子由鞘层边界向阴极运动过程中,离子能量分布的高能部分逐渐增大,角分布向小角度部分压缩,鞘层中的强电场加速和聚焦了离子;在鞘层边界附近的电场呈非线性。     

等离子体源离子注入球形靶的蒙特-卡罗模拟

建立了在球形靶鞘层中离子的蒙特-卡罗模拟模型,考虑了离子与中性粒子的电荷交换碰撞和弹性散射,以及精确依赖于入射离子能量的电荷交换碰撞截面和动量输运截面。模拟了不同气压下,在鞘层扩展过程中,氮离子N_2~+到达靶表面的能量分布和入射角分布,研究了它们的变化规律。     

衬底偏压对ECR等离子体鞘层和离子行为的影响

介绍了电子回旋共振微波放电等离子体中离子向衬底输运的蒙特卡罗模型,该模型考虑了精确依赖于离子能量的电荷交换和动量转移截面以及中性区与鞘层的衔接。     

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。     

原子和离子间激光感生碰撞电荷交换的微扰理论

将激光感生碰撞电荷看作一个四体系统，发展了激光感生碰撞电荷电荷的微扰理论，以独立原子和离子的复合态波函数作为激光感生碰撞体系的基组函数，得到了体系态振幅的运动方程。利用激光感生碰撞电荷交换的微扰理论，对Ｃａ＾＋－Ｓｒ间激光感生碰撞电荷交换进行了数值计算，并与Ｇｒｅｅｎ等人的实验结果进行了比较。     

离子推力器推力密度特性

离子推力器推力密度分布对航天器轨道维持和修正具有重要影响.采用粒子模拟-蒙特卡罗碰撞方法模拟束流等离子体输运过程,分析束流多组分粒子喷出数量和速度等微观参数,并计算得到单孔束流推力,结合放电室出口等离子体密度分布,进一步对推力密度分布特性分析,最后开展实验验证.研究结果显示:束流中单价离子、双荷离子以及交换电荷离子的推力贡献比分别为84.63%,15.35%和1.82%,可见推力主要来源于束流中的单价离子和双荷离子,交换电荷离子对推力贡献很小;推力密度分布具有较好的中心轴对称性,从推力器中心沿着径向先快速下降后趋于缓慢;与实验结果对比,经验模型相对误差约为4.1%,数值模型相对误差约为2.8%,相比经验模型,数值模型具有更好的准确性.研究结果可为离子推力器推力密度分布均匀性等优化提供参考.     

ECR微波等离子体源离子输运的蒙特卡罗模拟

采用蒙特卡罗方法，模拟了ＥＣＲ微波等离子体源中离子离开放电室后历经中性区，鞘层区，最后被加负偏压的工件表面吸收的全过程。研究了鞘层外界处的衔接问题，得到了自洽电势分布和鞘层区不同位置处的速度分布，能量分布与角分布。同时，讨论了磁场对鞘势的影响。     

Parameter space map of an electron cyclotron resonance plasma in acompact chamber

Ion current density measurements were made in an electron cyclotron resonance (ECR) plasma reactor for both argon and oxygen discharges. Spatial changes in the ion current density were also recorded across the reactor diameter for changes in pressure and power. These measurements revealed a minimum in the ion current density on the reactor axis. This observation has been explained as a consequence of the shape of the ECR region, which, in turn, is dependent on the mode of coupling. Current density measurements were made as a function of reactor pressure and microwave power for two different axial locations in the system. A Langmuir probe was also used at these two locations to measure the electron temperature as a function of these process conditions. It was observed that the ion current density and/or plasma density measured downstream from the ECR zone, increased significantly in the low-pressure/high-microwave power region. Results from this region of the operating parameter space have not previously been reported. Further existing models do not predict this observed increase in plasma density or ion current density. It has been proposed that a rarefication of the gas in the ECR region, as a result of gas heating, has acted to increase the outward diffusion of electrons from the ECR zone and, thus, has increased the ambipolar diffusion of ions to the downstream location. This proposal has been partially validated by experimental results in which the ion energy was measured as a function of reactor pressure and gas flow rate. The shape of the oxygen parameter space map differs significantly from that for Ar. The principal reasons for these changes are a number of different inelastic electron scattering mechanisms which effect the transport electrons out of the ECR zone and through ambipolar diffusion also the transport of ions. The second factor is the production of negative ionic species which varies with reactor pressure and, thus, T_e     

宽带微波馈入对于具有常规磁场构型的ECR离子源性能的提高

As clearly demonstrated at several laboratories,the performances of electron-cyclotron resonance (ECR)ion sources can be enhanced by increasing the physical sizes(volumes)of embedded ECR zones.En- larged ECR zones have been achieved by engineering the central magnetic field region of these sources so they are uniformly-distributed"volumes"in resonance with single-frequency rf power.Alternatively,the number of ECR surfaces in conventional minimum-B geometry sources can be increased by heating their plasmas with multiple,discrete frequency microwave radiation.Broadband rf power offers a simple,low cost and arguably more effective means for increasing the physical sizes of the ECR zones within the latter source type.In this article,theoretical arguments are made in support of the volume effect and the charge-state enhancing ef- fects of broadband microwave radiation(bandwidth:200MHz)plasma heating are demonstrated by comparing the high-charge-states of Ar ion beams,produced by powering a conventional minimum-B geometry,6.4GHz ECR ion source,equipped with a biased disk,with those produced by conventional bandwidth(bandwidth:～1.5MHz)radiation.     

电子回旋共振放电的电离特性PIC/MCC模拟(Ⅱ)——数值模拟与结果讨论

采用粒子模拟与蒙特卡罗相结合(PIC/MCC)的方法，应用电磁模型，编写了准三维的电子回旋共振(ECR)放电电离过程的模拟程序，得到了ECR放电过程中电子与离子的相空间分布、电磁场分布.通过对这些分布随时间演化的分析，得出ECR加热发生在ω≈ω_c0且垂直于轴向的区域；ECR区域，微波能量几乎全部耦合给电子，获得能量的电子通过与中性粒子的电离碰撞产生了大量的带电粒子；随着放电的进行，大量带电粒子通过频繁的碰撞，分布由各向异性逐渐趋于各向同性. 关键词： 电子回旋共振放电 粒子模拟 蒙特卡罗 电离     

Interaction between plasma and electromagnetic field in ion source of 10 cm ECR ion thruster

Through diagnosing the plasma density and calculating the intensity of microwave electric field, four 10 cm electron cyclotron resonance (ECR) ion sources with different magnetic field structures are studied to reveal the inside interaction between the plasma, magnetic field and microwave electric field. From the diagnosing result it can be found that the plasma density distribution is controlled by the plasma generation and electron loss volumes associated with the magnetic field and microwave power level. Based on the cold plasma hypothesis and diagnosing result, the microwave electric field intensity distribution in the plasma is calculated. The result shows that the plasma will significantly change the distribution of the microwave electric field intensity to form a bow shape. From the boundary region of the shape to the center, the electric field intensity varies from higher to lower and the diagnosed density inversely changes. If the bow and its inside lower electric field intensity region are close to the screen grid, the performance of ion beam extracting will be better. The study can provide useful information for the creating of 10 cm ECR ion source and understanding its mechanism.     

圆筒电极对离子磁电加热的影响

高效的磁电加热不仅能够提高电子回旋共振(ECR)等离子体的离子温度,还能改善离子的径向和轴向分布,促进ECR等离子体在化学气相沉积金刚石膜刻蚀中的应用.将磁电加热系统中的圆环电极改进为圆筒电极,研究了圆筒电极对离子磁电加热的影响,对比了圆筒和圆环电极加热离子的区别.结果表明:在同一阳极偏压下,圆筒比圆环电极更有利于提高离子温度,圆筒电极加热时各径向位置的离子温度升高的幅度较大,其中圆筒电极内部的离子温度径向分布差异较大,而圆筒下游的离子温度径向分布比较均匀;磁电加热对离子密度的影响很小;采用圆筒电极加热时,有利于离子向轴向下游的输运,改善了离子的轴向均匀性.     

ECR等离子体的磁电加热研究

在ECR等离子体装置上进行了磁电加热研究,利用离子灵敏探针(ISP)测量了磁电加热前后离子温度的变化,研究了电极环偏压、磁场强度、气压等参数对磁电加热过程以及加热效率的影响.结果表明:等离子体的整体加热是通过离子在电极环鞘层中的磁电加热及被加热的离子沿径向的输运来完成的.轴心处离子温度随电极环偏压的升高呈非线性增加.磁电加热效率随偏压的增大而增大,在电极环偏压为1000 V时,磁电加热效率为2%-2.5%,ECR等离子体中的离子温度能够提高20 eV以上.磁场强度在磁电加热过程中对离子的限制和加热起到重要作用,当磁场强度在6.3×10^-2-8.7×10^-2T之间变化时,磁电加热的效率随磁场强度的增大而增大.气压在0.02-0.8 Pa范围内,磁电加热的效率随气压的减小而增大. 关键词： ECR等离子体 磁电加热 离子温度     

ORNL-HRIBF 6GHzECR离子源的最新结果

Experimental studies were conducted to characterize and improve the performance of the flat-B ECR ion source.The emittance of the source was investigated for the first time.The output beam currents of high-charge-states of Ar(q>8)were nearly doubled by increasing the plasma electrode aperture from 4mm to 6mm in diameter.To investigate possible enhancements with broadband microwave radiation,a"white"Gaussian noise generator was employed with a TWT amplifier to generate microwave radiation with a bandwidth of～200MHz.The performance of the flat-B ECR ion source was found to be much better with narrow bandwidth radiation when the source was operated in the flat-B region.However,the ion beam intensities and charge state distributions were improved with the broadband radiation when the source was tuned off the flat-B region.