离子通道中环形束流分布与场解的自洽理论

考虑环形束流的空间电荷效应与相对论状态下的自磁效应对离子通道——环形束流系统的影响，研究了通道中环形束流的轨道与场解的自洽平衡态.利用动力学理论得到了电子平衡态分布函数以及环形束流的径向位置和通道内电磁场的自洽解.研究发现，相对论束流的自场对系统平衡态有很大影响，并证实了系统自洽平衡态的存在.数值计算给出了束流位置与通道半径间随能量的分布关系以及通道内场随半径分布的规律，为相关器件的设计提供了重要的理论数据. 关键词： 离子通道 环形束流 动力学理论 自洽平衡态     

Ion-Channel – Mimetic Sensors Based on Self-Assembled Monolayers of Phosphate Esters: High Selectivity for Trivalent Cations

 Gold electrodes were chemically modified with a phosphate ester monolayer designed to mimic biological ion-channel membranes. Cyclic voltammograms of Fe(CN)₆ ³⁻ as electroactive marker were measured in the presence of various types of analyte cations. Whereas in the absence of analyte cations the marker reduction was hindered by electrostatic repulsion between the marker anions and phosphate groups of the receptor monolayer, binding of di-and trications to the monolayer resulted in large increases of the reduction current. Trivalent cations could be detected down to the submicromolar concentration range with excellent selectivities over alkali metal ions. Also divalent cations were well discriminated and similar responses as to trivalent cations were only observed if their concentration exceeded that of the trivalent cations by about two orders of magnitudes. Received August 24, 1998. Revision March 10, 1999.     

Gain calculation of a free-electron laser operating with a non-uniform ion-channel guide

Amplification of an electromagnetic wave by a free electron laser (FEL) with a helical wiggler and an ion channel with a periodically varying ion density is examined. The relativistic equation of motion for a single electron in the combined wiggler and the periodic ion-channel fields is solved and the classes of possible trajectories in this configuration are discussed. The gain equation for the FEL in the low-gain-per-pass limit is obtained by adding the effect of the periodic ion channel. Numerical calculation is employed to analyse the gain induced by the effects of the non-uniform ion density. The variation of gain with ion-channel density is demonstrated. It is shown that there is a gain enhancement for group I orbits in the presence of a non-uniform ion-channel but not in a uniform one. It is also shown that periodic ion-channel guiding is used to reach the maximum peak gain in a low ion-channel frequency (low ion density).     

离子通道中相对论电子注的切连科夫辐射

对入射等离子体的相对论电子注(REB)在离子通道中可能产生切连科夫(Cherenkov)辐射的问题进行了论证与研究.利用线性理论分析了离子背景下的注-波互作用关系，导出了系统的色散方程与同步辐射条件.结果表明，系统的电磁不稳定性是由离子通道中TM模与电子注模通过电子注耦合所致，其微观机理是离子对电子注的聚焦.对处于运动等离子体状态下的离子-注系统进行了严格地理论分析，获得了通道内辐射波的频偏与波增长率公式，并通过数值模拟计算讨论了系统有关参数对它们的影响. 关键词： 离子通道 等离子体 切连科夫辐射     

Three-dimensional simulation of long-wavelength free-electron lasers with helical wiggler and ion-channel guiding

A three-dimensional simulation of a steady-state amplifier model of a long-wavelength free-electron laser (FEL) with realizable helical wiggler and ion-channel guiding is presented. The set of coupled nonlinear differential equations for electron orbits and fields of TE 11 mode in a cylindrical waveguide are solved numerically by the Runge-Kutta algorithm with averages calculated by the Gaussian quadrature technique. Self-fields and space-charge effects are neglected, and the electron beam is assumed to be cold and slippage is ignored. The parameters correspond to the Compton regime. Evolution of the radiation power and growth rate along the wiggler is studied. Ion-channel density is chosen to obtain optimum efficiency. Simulations are preformed for the FEL operating in the neighborhood of 35 GHz and 16.5 GHz for the electron beam energies of 250 keV and 400 keV, respectively. The result of the saturated efficiency was found to be in good agreement with the simple estimation based on the phase-trapping model.     

Electron acceleration in the inverse free electron laser with a helical wiggler by axial magnetic field and ion-channel guiding

Electron acceleration in the inverse free electron laser (IFEL) with a helical wiggler in the presence of ion-channel guiding and axial magnetic field is investigated in this article. The effects of tapering wiggler amplitude and axial magnetic field are calculated for the electron acceleration. In free electron lasers, electron beams lose energy through radiation while in IFEL electron beams gain energy from the laser. The equation of electron motion and the equation of energy exchange between a single electron and electromagnetic waves are derived and then solved numerically using the fourth order Runge-Kutta method. The tapering effects of a wiggler magnetic field on electron acceleration are investigated and the results show that the electron acceleration increases in the case of a tapered wiggler magnetic field with a proper taper constant.     

“Cold” dispersion relation of corrugated waveguide filled with plasma immersed in a finite magnetic field

A general dispersion equation of a partially filled plasma corrugated waveguide immersed in a finite magnetic field is presented. When the guiding magnet B_0→∞ or 0, this equation can be reduced to the results obtained in previous works.     

Dispersion relation and growth rate for a corrugated channel free-electron laser with a helical wiggler pump

The effects of corrugated ion channels on electron trajectories and spatial growth rate for a free-electron laser with a one-dimensional helical wiggler have been investigated. Analysis of the steady-state electron trajectories is performed by solving the equations of motion. Our results show that the presence of a corrugated channel shifts the resonance frequency to smaller values of ion channel frequency. The sixth-order dispersion equation describing the coupling between the electrostatic beam mode and the electromagnetic mode has also been derived. The dispersion relation characteristic is analyzed in detail by numerical solution. Results show that the growth rate of instability in the presence of corrugated ion channels can be greatly enhanced relative to the case of an uniform ion channel.     

仿生智能纳米通道在能量转换中的应用

智能纳米通道由于独特的纳米结构,导致对离子的通过具有选择性、整流性和门控性,从而在能量转换领域具有重要的应用前景。本文根据能量转换原理的不同,将纳米通道在能量转换中的应用分为:模仿电鳗鱼将化学能转换为电能,模仿绿叶将光能转换为化学能,模仿菌紫质将光能转换为电能,模仿水力发电机将流体机械能转换为电能。其中,模仿电鳗鱼系统由于广泛的能量来源、高的能量转换效率以及输出的能量形式为电能,应用前景最为广阔。能量转换的性能受纳米通道自身的几何结构以及内表面电荷密度的影响。除此之外,还受外界条件的影响,比如电解质溶液类型和浓度,浓差和气压差的大小以及pH值等。     

离子通道摇摆电子束流激发的纵向慢波不稳定性

考虑相对论电子束入射等离子体所产生的离子通道的具体结构,利用线性电磁流体力学理论对离子通道摇摆电子束激发的纵向慢波电磁不稳定性进行研究.通过对导出的系统色散关系的数值分析,给出了系统中电磁波、空间电荷波以及两者在一定条件下互作用形成的电磁-静电混合模式的传播特性.研究发现系统在慢波区域存在电磁不稳定性,并揭示此慢波不稳定性是由电子束的betatron振荡所导致,且系统的不稳定性程度与betatron振动频率密切相关.对betatron振荡激发的慢波电磁不稳定性物理机理进行了分析,并给出了不稳定性存在的条件 关键词： 离子通道 betatron振荡 电磁不稳定性