离子导体在离子输运状态下的物理特性

1974年杨桢等发现α-LiIO_3单晶在直流电场作用下,中子衍射强度显著增强现象后,引起了中国物理学家们的强烈兴趣。特别是中国科学院物理研究所的物理学家们研究了离子导体在静电场作用下的介电行为,X射线形貌图,光衍射,喇曼散射,超声衰减等等,观察到了许多新现象,并对这些现象的机制作了理论解释,本文将对这些实验和理论结果作一评述。     

掺稀土离子的CaS：Bi荧光粉的发光性质

采用固相反应法合成了单掺和双掺稀土离子Ｔｍ３＋、Ｅｒ３＋的ＣａＳ：Ｂｉ荧光粉，测定了试样的荧光光谱和有效余辉。与ＣａＳ：Ｂｉ相比，掺入Ｔｍ３＋、Ｅｒ３＋的荧光粉，Ｂｉ３＋特征发射峰４４７ｎｍ增强，有效余辉延长。表明Ｔｍ３＋、Ｅｒ３＋对Ｂｉ３＋在ＣａＳ中的发光产生了敏化作用，Ｔｍ３＋、Ｅｒ３＋在基质晶格中造成了缺隙深能级，讨论了Ｔｍ３＋、Ｅｒ３＋对ＣａＳ：Ｂｉ发光敏化作用的大小和在基质中造成缺隙能级。的深浅。     

Pulsed Ion Sheath Dynamics in a Cylindrical Bore for Inner Surface Grid—Enhanced Plasma Source Ion Implantation

Based on our recently proposed grid-enhanced plasma source ion implantation(GEPSII) technique for inner surface modification of materials with cylindrical geometry,we present the corresponding theoretical studies of the temporal evolution of the plasma ion sheath between the grid electrode and the target in a cylindrical bore.Typical results such as the ion sheath evolution,time-dependent ion density and time-integrated ion energy distribution at the target are calculated by solving Poisson‘s equation coupled with fluid equations for collisionless ions and BOltzmann assumption for electrons using finite difference methods.The calculated results can further verifty the feasibility and superiority of this new technique.     

射频离子阱中氖离子的电荷转移

本文报导的是存在射频离子阱中的氖离子与氖气的电荷转换率的测量，其结果好于Ｐｅｎｎｉｎｇ阱。     

实时单发测量的汤姆逊离子谱仪

介绍一种使用闪烁体耦合电子倍增电荷耦合器件（EMCCD）的方式对离子进行记录的汤姆逊能谱仪,可实现对离子能谱的实时单发测量。同时,该谱仪利用倾斜电极板对离子进行偏转,可减少由于离子打在电极板上产生的电磁噪声,能够提高实验结果的信噪比。该谱仪在北京大学4.5 MV静电加速器和26 MV串列加速器上进行了标定实验,测量了闪烁体将离子转化成光子后的探测效率,实验结果也验证了该谱仪的可行性和稳定性。该汤姆逊谱仪将用于北京大学激光加速器CLAPA对离子束流的测量研究。     

Cross Sections of Electron Detachment for Si^- and Ge^- in Collision with Ar

Single electron detachment cross section for 10-40keV Si^- and Ge^- in collisions with Ar are measured and compared with other available experimental results. In our experimental energy region, the trend of cross sections is almost constant. The cross sections of Ge larger than Si can be understood by including electron affinity and size of negative ions.     

Reformed Solitary Kinetic Alfven Waves due to Dissipations and Auroral Electron Acceleration

The physical nature of the auroral electron acceleration has been an outstanding problem in space physics for decades. Some recent observations from the auroral orbit satellites, FREJA and FAST, showed that large amplitude solitary kinetic Alfvén waves (SKAWs) are a common electromagnetic active phenomenon in the auroral magnetosphere. In a low-β (i.e., β/2<<m_e/m_i<<1) plasma, the drift velocity of electrons relative to ions within SKAWs is much larger than thermal velocities of both electrons and ions. This leads to instabilities and causes dissipations of SKAWs. In the present work, based on the analogy of classical particle motion in a potential well, it is shown that a shock-like structure can be formed from SKAWs if dissipation effects are included. The reformed SKAWs with a shock-like structure have a local density jump and a net field-aligned electric potential drop of order of m_ev_A²/e over a characteristic width of several λ_e. As a consequence, the reformed SKAWs can efficiently accelerate electrons field-aligned to the order of the local Alfvén velocity. In particular, we argue that this electron acceleration mechanism by reformed SKAWs can play an important role in the auroral electron acceleration problem. The result shows that not only the location of acceleration regions predicted by this model is well consistent with the observed auroral electron acceleration region of 1—2 R_E above the auroral ionosphere, but also the accelerated electrons from this region can obtain an energy of several keV and carry a field-aligned current of several μA/m² which are comparable to the observations of auroral electrons.     

Influence of Ion Nonlinear Polarization Drift and Warm Ions on Solitary Kinetic Alfvén Wave

Considering the effects of ion nonlinear polarization drift and warm ions, we adopt two-fluid model to results derived in this paper indicate that dip SKAW and hump SKAW both exist in a wide range in magnetosphere(for the pressure parameter β ~ 10-5 ~ 0.01, where βis the ratio of thermal pressure to magnetic pressure, i.e.region 1 > β > me/mi. These results are different from previous ones. That indicates that the effects of ion nonlinear polarization drift and warm ions are important and they cannot be neglected. The SKAW has an electric field parallel to the ambient magnetic field, which makes the SKAW take an important role in the acceleration and energization of field-aligned charged particles in magnetic plasmas. And the SKAW is also important for the heating of a local plasma.So it makes a novel physical mechanism of energy transmission possible.     

Theory of Shear Alfven Vortex in Current-Carrying Plasma Plasma

Nonlinear shear Alfven waves in low P, current-carrying magnetized plasma are studied.Sets of nonlinear equations describing the shear Alfven waves are derived and corresponding dipolar vortex solutions are given for both regions of P, 0<β< m_e/m_i and m_e/m_i<<β<<1, respectively. Result shows that the equilibrium plasma current has remarkable effect on the behaviour of vortex motion. For the 0<β<< m_e/m_i case the current adds a low speed vortex propagating region in the opposite current direction, while for the < m_e/m_i<<β<<1 case the current reduces the region of vortex propagating speed by cutting a low speed region. The implication of this effect is discussed.     

A relation between the resonance neutron peak and ARPES data in cuprates

We argue that the resonant peak observed in neutron scattering experiments on superconducting cuprates and the peak/dip/hump features observed in ARPES measurements are byproducts of the same physical phenomenon: both are due to feedback effects on the damping of spin fluctuations in a d-wave superconductor. We argue that in the superconducting phase, the dynamical spin susceptibility possesses the resonance peak at Ω_res∝ξ⁻¹ where ξ is the magnetic correlation length. The scattering of the resonant magnetic excitations by electrons gives rise to a peak/dip/hump behavior of the electronic spectral function, the peak-dip separation is exactly Ω_res.     

Study on υμ, υγ, Decays and CP Non-Invariance at Early Epoch of the Universe

We study the υ_μ and υ_γ decays in the early epoch of the universe. If m_υγ > 2m_e, there would be a CP asymmetry between υ_γ→e⁺+e^-+υ_e and υ_γ→e⁺+ e^-+ υ_e. The resultant CP non-invariance is a function of temperature and density and can reach l0^-7 for a reasonable temperature range, but it is noticed that if m_υγ > 2υ_μ～200 MeV, the CP non-invariance can be much larger.     

Polarization control of microwave emission from high powerrectangular cross-section gyrotron devices

Results are summarized of experiments on a gyrotron utilizing a rectangular-cross-section (RCS) cavity region. The major issue under investigation is polarization control of microwave emission as a function of magnetic field. The electron beam driver is the Michigan Electron Long Beam Accelerator (MELBA) at parameters: V=0.8 MV, I_diode=1-10 kA, I_tube=0.1=0.5 kA, and t_e-beam=0.4-1.0 μs. The annular e-beam is spun up into an axis-encircling beam by passing it through a magnetic cusp prior to entering the RCS interaction cavity. Experimental results show a high degree of polarization in either of two orthogonal modes as a function of cavity fields. The RCS gyrotron produced peak powers of 14 MW in one polarization (TE₁₀) and 6 MW in the cross-polarized mode (TE ₀₁). Electronic efficiencies for this device reached as high as 8% with transverse efficiency of 16%. Experimental results on the beam alpha (α=V_⊥/V_∥) diagnostics, where alpha is the ratio of the e-beam's transverse velocity to its parallel velocity, agree well with the single electron trajectory code. MAGIC code results are in qualitative agreement with microwave measurements. Microwave emission shifts from the dominant fundamental mode polarization (TE₁₀□ ), to the next higher order mode polarization (TE₀₁□) as the solenoid magnetic field is raised from 1.4-1.9 kGauss. Frequency measurements using heterodyne mixers support mode identification as well as MAGIC code simulations     

极化检测型铷原子磁力仪的研究

针对交变弱磁场的检测,研制了一种基于极化-检测双光束结构的激光抽运铷原子磁力仪.为了获得该磁力仪对磁场的响应特性,通过数值仿真分析了信号幅度随极化磁场强度、弛豫时间的变化关系,并进行了实验验证.最后通过选择合适的极化磁场使磁力仪对待测磁场的灵敏度最大.实验结果表明,优化后磁力仪灵敏度为0.2pT/(Hz)~(1/2),响应带宽3.5kHz,可用于弱磁场磁共振、高频异常物理现象等信号的检测.     

Effects of Ion Temperature and Inertia on Kinetic Alfvén Waves

Kinetic Alfvén wave (KAW) has been an interesting topic for discussion extensively in the fields of labora-tory, space, and astrophysical plasmas. A general dispersion equation is derived from the exact two-fluid model in thisambient magnetic field. For the short wavelength cases of kλi >> 1, where λi = vA/ωci and ωci are the ion inertial lengthand gyrofrequency, respectively, our dispersion relations are appropriate for discussing effects of the ion temperatureand inertia on KAWs. The present results show that both the ion temperature and inertia can affect considerably thebehaviors of KAWs in propagation, resonance, and polarization. In particular, our results may be a great help to un-derstanding some salient features of the low-frequency (in comparison with the ion gyrofrequency ωci) electromagneticfluctuations frequently observed by the FREJA and FAST satellites in the auroral zone of the Earth's ionosphere andmagnetosphere.     

Super-Alfvénic propagation of substorm reconnection signatures and Poynting flux

The propagation of reconnection signatures and their associated energy are examined using kinetic particle-in-cell simulations and Cluster satellite observations. It is found that the quadrupolar out-of-plane magnetic field near the separatrices is associated with a kinetic Alfvén wave. For magnetotail parameters, the parallel propagation of this wave is super-Alfvénic (V(∥) ～ 1500-5500 km/s) and generates substantial Poynting flux (S ～ 10(-5)-10(-4) W/m(2)) consistent with Cluster observations of magnetic reconnection. This Poynting flux substantially exceeds that due to frozen-in ion bulk outflows and is sufficient to generate white light aurora in Earth's ionosphere.     

Identification of the electron-diffusion region during magnetic reconnection in a laboratory plasma

We report the first identification of the electron-diffusion region, where demagnetized electrons are accelerated to super-Alfvénic speed, in a reconnecting laboratory plasma. The width of the electron-diffusion region scales with the electron skin depth [ approximately (5.5-7.5)c/omega_{pe}] and the peak electron outflow velocity scales with the electron Alfvén velocity [ approximately (0.12-0.16)V_{eA}], independent of ion mass.