反场构型等离子体靶压缩过程中强磁场对α粒子能量的约束效应

基于一维弹塑性磁流体力学程序（SSS-MHD）,研究了反场构型（FRC）等离子体靶在磁驱动固体套筒压缩过程中强磁场对α粒子能量约束效应,分析了α粒子的非局域和局域自加热对FRC等离子靶压缩峰值温度的影响,以及α粒子能量在整个压缩过程中端部损失效应。等离子体部分采用多温单流体的模型,能量的计算中引入了DT离子、电子及α粒子多成分温度的能量方程,同时考虑了等离子体压缩过程热平衡下的核反应和非局域自加热问题。研究结果表明,磁化靶聚变等离子体在压缩过程中具有较好的稳定性,能够保持刚性转子的靶结构,压缩过程形成的强磁场能够将α粒子的能量约束在O点附近的区域,有利于等离子体靶的点火及燃烧;α粒子对等离子体的自加热效应主要集中在等离子体电流中心区,而非等离子体中心轴处;α粒子对DT等离子体局域和非局域自加热过程存在差异,局域自加热过程的功率大于非局域自加热过程的功率,FRC等离子靶压缩峰值状态温度相差0.5倍。在反场构型的刮离层区,α粒子的能量端部损失在FRC等离子体靶的压缩和膨胀过程中逐渐增大。     

托卡马克等离子体中共振磁扰动场放大效应对离子轨道特性的作用

首先,利用MARS-F程序模拟了HL-2A装置中不同电阻率、环向旋转频率和环向模数条件下等离子体对共振磁扰动(RMP)的线性响应过程,分析了不同情况下共振场放大效应对三维扰动磁场的影响;然后,利用Boris算法追踪了三维场作用下的离子轨道,并详细探究了不同扰动磁场改变离子轨道特性的物理机制.研究发现,考虑等离子体响应后的扰动磁场可增强离子轨道径向展宽,且轨道最大径向展宽随轨道上扰动磁场平均值的增大而增大;同时,离子在通过扰动磁场被强烈放大的区域时轨道径向展宽会显著增加.该物理机制可用于解释RMP缓解边界局域模实验中离子直接损失增加和等离子体径向输运增强现象.     

托卡马克装置中等离子体环向旋转对三维响应场的影响

本文利用MARS-F程序,数值研究了HL-2M托卡马克装置高比压等离子体中,环向旋转对外加共振磁扰动场的响应特性的影响.研究发现,等离子体响应显著改变共振磁扰动的谱分布,并影响等离子体内部共振磁扰动场与共振磁扰动线圈电流相位差的依赖关系,从而改变有理面处径向扰动场的幅值.当边界旋转频率较小时,在最外有理面处,等离子体响应对外加共振磁扰动场有明显的放大效应.通常,边缘局域模的控制效果依赖于最外有理面处共振磁扰动场的幅度,因此可通过控制旋转剖面实现对共振磁扰动场的调控,进而优化边缘局域模的控制方案.     

局域热源对磁岛热输运的影响

研究托卡马克等离子体磁岛内的热输运行为.应用局域高斯热源对磁岛加热来模拟电子回旋共振加热.对同时存在背景热源与局域高斯热源的情况,观察局域高斯热源对径向电子温度分布及热输运产生的变化,分析局域高斯热源对温度扰动及磁岛约束能量的影响.     

HL-2A托卡马克上的边缘局域模特性初步研究

高约束模式(H模)下自发产生的边缘局域模(ELM),虽然利于控制等离子体密度和排出杂质粒子从而实现H模放电的稳态运行,但是ELM爆发携带的大量粒子和能量会对装置的第一壁材料造成很大的损坏,所以在下一代聚变装置上使用之前很多装置已经开始了对ELM的研究.在HL-2A装置上观察到了不同的ELM,扰动幅度小的ELM引起的等离子体储能损失小于3%,ELM之间的时间间隔约为3 ms,表现出Ⅲ型ELM的特征;扰动幅度较大的ELM的爆发对等离子体电流、等离子体密度及储能都有很明显的扰动,对等离子体储能的扰动大于10%,ELM爆发的频率随通过等离子体磁分界面的净加热功率的增加而增加,表现出明显的Ⅰ型ELM的特征.ELM先兆有不对称性,在弱场侧磁探针信号能观测到,但强场侧却观测不到;ELM先兆的频率约为45 kHz,观测到的最长的先兆先于ELM前约10ms出现.     

CFETR上高能量粒子输运初步模拟研究

为了研究CFETR上高能量粒子的行为,利用输运代码ONETWO模拟研究了聚变反应和高能量粒子的输运现象。在无中性束注入(NBI)条件下,高能量α粒子的密度是随时间逐渐减少的。在考虑NBI以后,α粒子密度有着较明显的下降。在束离子能量增加而NBI功率不变的情况下,α粒子密度除了在等离子体中心区域有一定的下降外,在其他区域几乎没有变化。在NBI功率增加而束离子能量不变的情况下,α粒子密度在等离子体中心区域有着明显的下降。     

等离子体形变对边界局域模的作用研究

在磁流体模拟代码BOUT++剥离气球模三场模块框架下研究了等离子体形变参数(拉长比和三角形变)对边界局域模的影响。研究表明，在线性阶段，拉长比主要作用于剥离气球模中气球模成分，抑制了环向模数较高的气球模不稳定性；而三角形变则对剥离气球模中剥离模成分和气球模成分均有抑制作用。在非线性阶段，拉长比导致边界E×B剪切率增加，迫使压强扰动的正值部分向等离子体芯部发展，导致边界局域模的能量损失增加；三角形变则导致边界E×B剪切率降低，使得压强扰动可以向等离子体边缘发展，台基向等离子体芯部的崩塌减弱，从而对边界局域模起到缓解作用。     

HL-1M装置逃逸电子输运系数的研究

采用磁扰动实验和稳态实验等四种不同方法获得某些局域的逃逸扩散系数Dr。利用等离子体快速移动实验，测量了孔栏上硬X射线通量的变化，获得了边缘扩散系数，利用软X射线强度和硬X射线通量信号的锯齿振荡峰值延迟时间得出了径向平均扩散系数，用微波辐射强度和硬X射线通量信号的锯齿振荡 峰值延迟时间，获得了径向位置某处到孔栏之间的平均扩散系数。用来自孔栏上的韧致辐射谱求出逃逸电子的平均能量，得玻逃逸约束时间和径向平均扩散系数，实验中还得到了逃逸电子扩散系数的径向近似分布和内部磁扰动的径向分析。     

带电粒子与磁化等离子体相互作用的极化效应及能量损失

 利用线性Vlasov-Poisson方程,研究了带电粒子在磁化二份量等离子体中运动时产生的动力学极化效应及能量损失,重点分析了外磁场及等离子体中离子的极化效应对入射粒子能量损失响。数值结果表明：入射粒子的能量损失有两个峰,分别位于高速区和低速区,对应于等离子体中的电子极化效应和离子极化效应。在强磁场情况下,低速粒子的能量损失主要来自离子的极化效应;而在弱磁场情况下,高速粒子的能量损失则主要来自于电子的极化效应。     

磁镜场对射频等离子体中离子能量分布的影响

运用阻碍栅极型能量分析器,在不同磁镜场参数下测量了低温等离子体中离子的能量分布. 结果表明,在放电管中心处离子能量分布,随磁镜场强度的增加而向低能方向偏移,但离子能量分布宽度却没有明显的变化;而随着磁镜比的增加离子能量分布却向高能方向偏移,并且离子能量分布宽度也将变宽.由此可见,磁镜场参数对离子能量分布有很大影响. 关键词： 磁镜场 辉光放电 低温等离子体 离子能量分布     

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Based on ORBIT code of a guiding center motion of single particle, the loss of energetic ions in different radial positions of tokamak plasma is studied by using test particle simulation method. The results show that the local magnetic perturbations can cause loss of many energetic ions near the central region of the plasma, but they have little effect on the ion loss near the plasma boundary, assuming that the local field is mainly located near a magnetic surface and its toroidal field is similar to the ripple field. These energetic ions are trapped ions, and the greater their pitch angle is, the easier they lose. In addition, the radial position of the local field that causes the maximum loss rate of energetic ions is usually offset from the initial radial position of these loss ions, and this shift is closely related to the energy of these ions. When the local field appears in certain locations, the ions of lower energy have some loss, but the ions higher energy does not lose.     

Dust charging and levitating in a sheath of plasma containing energetic particles

The structure of the sheath in the presence of energetic particles is investigated in the multi-fluid framework. Based on the orbital motion limited(OML) theory, the dust grain charging inside the sheath of plasma containing energetic particles is examined for the carbon wall, and then the effect of the energetic particles on the stationary dust particle inside the sheath is discussed through the trapping potential energy. It is found that with the increase of energetic ion concentration or energy,the size of dust staying in levitation equilibrium decreases and the levitating position is much closer to the wall. In the case of deuterium ions as energetic ions, the bigger dust particle can be trapped by the sheath than in the case of hydrogen ions as energetic ions. When the energetic electron component is present, the levitating position of dust particle in the sheath depends strongly on the energetic electron. The levitating dust particle is closer to the wall as the energetic electron energy or concentration is increased. In addition, with the increase of temperature of thermal background ion, the size of dust particle trapped by the sheath decreases and the levitating positions of dust particles with the same size radius inside the sheath move toward the wall. Our results can be helpful in investigating the property of the sheath where the energetic particle component is present.     

Effect of trapped energetic ions on MHD activity in spherical tori

It is shown that the increase of β (the ratio of plasma pressure to the magnetic field pressure) may change the character of the influence of trapped energetic ions on MHD stability in spherical tori. Namely, the energetic ions, which stabilize MHD modes (such as the ideal kink mode, collisionless tearing mode and semi-collisional tearing mode) at low β, have a destabilizing influence at high β unless the radial distribution of the energetic ions is very peaked.     

Gd靶激光等离子体6.7nm光源的实验研究

本文对Gd靶激光等离子体极紫外光源进行了实验研究, 在 6.7 nm附近获得了较强的辐射, 并研究了6.7 nm 附近光辐射随打靶激光功率密度变化的规律以及收集角度对极紫外辐射的影响. 同时, 对平面Gd靶激光等离子光源的离子碎屑角分布进行了测量, 发现从靶面的法线到沿着靶面平行方向上Gd离子数量依次减少. 进一步研究结果表明采用0.9 T外加磁场的条件下可取得较好的Gd 离子碎屑阻挡效果.     

先进磁镜装置中径向电场对高能粒子的约束性能研究

本文运用Boris算法对紧凑型聚变反应装置(compact fusion reactor, CFR)中高能a粒子的运动轨道进行了数值模拟,分析了高能a粒子在不同径向电场作用下运动轨道的差异性;探究了不同径向电场对CFR装置中不同位置处a粒子约束性能的影响.研究结果表明,当正、负径向电场强度达到一定临界值时,都能够使高能a粒子很好地约束在CFR装置内部,但不同位置处径向电场强度临界值与a粒子初始条件有关.     

快重离子束实现点火的可行性

采用蒙特卡罗方法计算了低温下C,Si,Ar,Au和U等多种重粒子在等物质的量氘氚等离子体密度1000 g/cm3、热斑直径50 m中的电子能量损失,不同点火形式下入射能量和作用时间,以及燃料约束时间为20 ps条件下的束流强度。通过对数据的分析研究了这些重粒子辐照实现氘、氚燃料快点火的可能性。结果表明,重粒子束流加热等离子体实现快点火理论上可行,而且有一定的优势;较重的离子加热聚变等离子体的效果更好。重粒子束流加热等离子体到聚变温度需要的束流强度在MA左右;单个粒子的能量在GeV以上;相互作用时间为ps以下。     

DC column plasma kinetics in a longitudinal magnetic field

The cylindrical column plasma of a neon dc glow discharge under the influence of a weak longitudinal magnetic field is studied. An extended, fully self-consistent model of the column plasma has been used to determine the kinetic quantities of electrons, ions and excited atoms, the radial space charge field, and the axial electric field for given discharge conditions. The model includes a nonlocal kinetic treatment of the electrons by solving their spatially inhomogeneous kinetic equation, taking into account the radial space charge field and the axial magnetic field. The treatment is based on the two-term expansion of the velocity distribution and comprises the determination of its isotropic and anisotropic components in the axial, radial, and azimuthal direction. A transition from a distinctly nonlocal kinetic behavior of the electrons in the magnetic-field-free case to an almost local kinetic behavior has been found by increasing the magnetic field. The establishment of the electron cyclotron motion around the column axis increasingly restricts the radial electron energy transport and reduces the radial ambipolar current. The complex interaction of these transport phenomena with the alterations in the charge carrier production leads finally to a specific variation of the electric field components. The axial field increases by applying weak magnetic fields, however, decreases with increasingly higher magnetic fields. At higher magnetic fields, the radial space-charge field is considerably reduced     

Radial Distributions of Dusty Plasma Parameters in a DC Glow Discharge

A non‐stationary non‐local kinetic model for radial distributions of dusty plasma parameters based on the solution of Boltzmann equation for electron energy distribution function is presented. Electrons and ions production in ionizing collisions and their recombination on dust particle surface were taken into account. The drift‐diffusion approximation for ions was used. To obtain the self‐consistent radial distribution of electric potential the Poisson equation was used. It is shown that at high dust particle density the recombination of electrons and ions can exceed their production in ionization collisions in the region of dusty cloud. In this case the non‐monotonous radial distribution of the electric field is formed, the radial electric field becomes reversed and the radial electron and ion fluxes change their direction toward the center of the tube (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Observation of centrifugally driven interchange instabilities in a plasma confined by a magnetic dipole

Centrifugally driven interchange instabilities are observed in a laboratory plasma confined by a dipole magnetic field. The instabilities appear when an equatorial mesh is biased to drive a radial current that causes rapid axisymmetric plasma rotation. The observed instabilities are quasicoherent in the laboratory frame of reference; they have global radial mode structures and low azimuthal mode numbers, and they are modified by the presence of energetic, magnetically confined electrons. Results from a self-consistent nonlinear simulation reproduce the measured mode structures.