Stabilization of counter streaming electron beam instability

Instability at half the electron cyclotron frequency that arises in a system of symmetrical counter streaming electron beams is stabilized by the injection of third beam.     

损失锥-束流分布电子驱动的回旋激射不稳定性

在Chen等理论模型的基础上，对损失锥-束流分布电子激发的回旋激射不稳定性的主要特征 进行了深入研究，这种电子分布在太阳色球附近的磁重联过程中可能形成，它兼有束流和损 失锥的特性.结果表明，它不仅可以像束流分布和损失锥分布那样在适当的等离子体频率和 回旋频率的比值范围内激发X模和O模的基频和谐频不稳定性，兼有两种分布的激发特性，而 且具有更强的增长率.这一方面丰富了此类等离子体不稳定性的基本内容，而且预期在天体 射电发射机理的研究中也将得到广泛的应用. 关键词： 回旋激射不稳定性 弱相对论性 损失锥-束流分布电子 增长率     

分子束频率分布函数的研究

从分子束的速率分布函数出发,推导了分子束的频率分布函数,求出平均频率、方均根频率和最概然频率,并与分子束的速率分布函数相应的特征物理量逐一比较,说明它们的物理意义,得出了用分子束的频率分布函数解决分子束问题更为简便的结论．     

Neutrino beam plasma instability

We derive relativistic fluid set of equations for neutrinos and electrons from relativistic Vlasov equations with Fermi weak interaction force. Using these fluid equations, we obtain a dispersion relation describing neutrino beam plasma instability, which is little different from normal dispersion relation of streaming instability. It contains new, nonelectromagnetic, neutrino-plasma (or electroweak) stable and unstable modes also. The growth of the instability is weak for the highly relativistic neutrino flux, but becomes stronger for weakly relativistic neutrino flux in the case of parameters appropriate to the early universe and supernova explosions. However, this mode is dominant only for the beam velocity greater than 0.25c and in the other limit electroweak unstable mode takes over.     

Energy distribution extraction of negative charges responsible for positive bias temperature instability

A new method is proposed to extract the energy distribution of negative charges, which results from electron trapping by traps in the gate stack of n MOSFET during positive bias temperature instability(PBTI) stress based on the recovery measurement. In our case, the extracted energy distribution of negative charges shows an obvious dependence on energy,and the energy level of the largest energy density of negative charges is 0.01 e V above the conduction band of silicon. The charge energy distribution below that energy level shows strong dependence on the stress voltage.     

Nonlinear stabilization of beam instability

If a high-frequency field affects the dielectric properties of the plasma, it can be shown that this results in a dependence of the frequency of natural plasma oscillations on the field amplitude. So, the beam and the excited waves get out of resonance, the instability weakens and sometimes may totally vanish.     

Computation of two-stream explosive instability including harmonics generation and distribution function evolution

Self-consistent computation of the two-stream explosive instability revealed an abrupt and almost complete deceleration of the streams accompanied by saturation of the explosive growth and formation of a turbulent state.     

CSNS/RCS中的阻抗和束流不稳定性

中国散裂中子源（CSNS）的快循环同步加速器（RCS）是一台强流质子加速器,其束流平均功率达到100 kW。在此强流加速器中,真空部件的阻抗是引起束流不稳定的主要原因,它严重限制了束流强度及品质。对CSNS/RCS设计中的各种真空部件阻抗进行了详细计算,并以计算结果为出发点,理论分析了各种不稳定性强弱,确定了各种不稳定性发生的阻抗阈值,为真空部件结构设计提供了参考。对比较严重的电阻壁阻抗,采用阻抗壁尾场模型进行跟踪模拟,得到不稳定性增长率与理论计算值符合较好。自然色品有助于束流稳定,加入自然色品后模拟,电阻壁不稳定性消失。     

Electron energy distribution function in a collisional plasma heated by an electron beam

The electron energy distribution function for the non-resonant electrons in a collisional weakly ionized plasma is found, provided that the intensity of the Langmuir oscillation is spatially dependent. It is assumed that electron-electron collisions are responsible for energy loss.     

CSNS/RCS中的阻抗和束流不稳定性

中国散裂中子源（CSNS）的快循环同步加速器（RCS）是一台强流质子加速器,其束流平均功率达到100 kW。在此强流加速器中,真空部件的阻抗是引起束流不稳定的主要原因,它严重限制了束流强度及品质。对CSNS/RCS设计中的各种真空部件阻抗进行了详细计算,并以计算结果为出发点,理论分析了各种不稳定性强弱,确定了各种不稳定性发生的阻抗阈值,为真空部件结构设计提供了参考。对比较严重的电阻壁阻抗,采用阻抗壁尾场模型进行跟踪模拟,得到不稳定性增长率与理论计算值符合较好。自然色品有助于束流稳定,加入自然色品后模拟,电阻壁不稳定性消失。     

Iterative nonlinear beam propagation using Hamiltonian ray tracing and Wigner distribution function

We present an iterative method for simulating beam propagation in nonlinear media using Hamiltonian ray tracing. The Wigner distribution function of the input beam is computed at the entrance plane and is used as the initial condition for solving the Hamiltonian equations. Examples are given for the study of periodic self-focusing, spatial solitons, and Gaussian-Schell model in Kerr-effect media. Simulation results show good agreement with the split-step beam propagation method. The main advantage of ray tracing, even in the nonlinear case, is that ray diagrams are intuitive and easy to interpret in terms of traditional optical engineering terms, such as aberrations, ray-intercept plots, etc.     

强激光在磁化等离子体中的调制不稳定性

采用洛伦兹变换推导出左旋椭圆偏振强激光在磁化等离子体中的非线性色散关系,根据Karpman方法推导出激光场包络的非线性控制方程,分析了在磁化等离子体中左旋椭圆偏振激光的调制不稳定性,得到了调制不稳定的时间增长率。分析结果表明,磁化等离子体中自调制不稳定的极大增长率较非磁化情况明显减小,且在激光等离子体临界面附近处调制不稳定性的时间增长率显著增大。