有限β环形等离子体二维漂移波本征模方程

本文从略去碰撞项的漂移动力方程出发,利用同心圆截面托卡马克位形,在m_e/m_i≤β<<1的条件下(m_i及m_e分别是离子和电子的质量),导出了有限β环形等离子体二维本征模方程。所得方程可以用来研究二维低频漂移波及高m气球模的稳定性。     

环形等离子体平衡时维持场电流的计算

本文介绍一个计算轴对称任意截面环形等离子体平衡问题的方法。先选定等离子体边界和环电流分布,用有限元方法解平衡方程的边值问题。借助于虚壳原理,得到用平衡方程解表示的能够产生平衡时所需要的维持场的虚壳电流。计算虚壳电流在等离子体区的维持场,以它为根据,采用积分方程开拓,求等离子体区外某位形上的维持场电流分布。解决这个问题的主要困难是当磁场向外开拓时遇到了不适定问题。我们用奇异值分解方法解不适定的Fredholm第一类积分方程。这个方法能容易地找到稳定解,对解决这个平衡问题是简单有效的。我们以七种等离子体截面形状,三种电流分布为具体模型,在三种维持场电流分布位形上给出了维持场电流分布。还给出了维持场形态,维持场总电流与等离子体总电流的比较,并简单讨论了维持场对等离子体整体稳定性的影响。 关键词：     

托卡马克中快波电流驱动下全波方程的数值求解

用全波方法研究环形对称托卡马克等离子体中离子回旋频率范围内(ICRF)的快波电流驱动(FWCD)问题,考虑有限拉莫尔半径(FLR)效应和平行色散,建立全波计算的物理模型—全波方程,通过对全波方程的数值求解得到快波在等离子体中激发的电场强度分布.结果表明:快波可以传播到高温高密度等离子体的中心;快波在磁轴附近发生了模式转换;快波可以驱动中心的等离子体电流以改善等离子体的平衡位型;平行电场比垂直电场小三个数量级,通过垂直方向的回旋共振和平行方向的穿越期磁泵效应达到驱动电流的目的.     

环形系统双成份等离子体中快波离子回旋共振加热

本文考虑环形系统双成份等离子体中快波电场与少数成份离子共振时,快波经回旋阻尼以加热等离子体。假定粒子间接近无碰撞,沿特征线积分Vlasov方程的方法求一级分布函数及各类粒子贡献的电流。因为少数成份粒子密度与多数成份粒子密度之比为小量,不难求解等离子体内精确到一级的电场。从而求得快波回旋阻尼功率。对于一个具体的激发系统,由边条件求解场系数,得到了通过快波回旋阻尼加热等离子体的功率。     

负磁剪切环形等离子体中的电子温度梯度不稳定性研究

本文用本征模积分方程研究了环形等离子体中磁剪切为负时由电子温度梯度驱动的不稳定性。考虑了电子的全部动力学效应，强调了稳定性阈值附近的模式行为及相应的湍性输运，给出了磁剪切为负的临界梯度的拟合公式。     

有相对论效应的二维Fokker-Planck程序包的开发与应用

求解没有相对论效应的Fokker-Planck方程的程序包已于2002年完成。求解有相对论效应的Fokker-Planck方程的程序包，由意大利引进，该程序包是反跳平均的，考虑了捕获电子效应、各种不同加热模式下的准线性扩散系数。可用于描述托卡马克辅助加热情形的等离子体粒子的动力学过程，能够计算环形几何下电子和离子的分布函数，包含了波加热，中性束注入，粒子损失等效应。对HL-1M装置和HL-2A装置的实验数据分析非常有用。     

环形波导狭缝天线产生的氩等离子体特性研究

研制了一种环形波导腔环绕直径３０ｃｍ,高５０ｃｍ耐热玻璃圆筒真空室构成的新的大面积微波等离子体源。环形波导内侧开有多个用来激励产生等离子体的狭缝,相邻狭缝间的距离为半个波导波长。利用该装置研究了微波功率,工作气体对氩等离子体特性的影响。     

有限磁场作用下等离子体圆柱波导中的线性理论

 考虑了有限磁场的作用,利用“匹配场法”推导出填充环形等离子体时圆柱波导的色散方程,并较详细地讨论了等离子体的厚度、密度, 以及所加磁场强度对色散特性的影响。尤其讨论了等离子体厚度对增长率的影响并得出：对应最大的增长率有一最佳的等离子体厚度。     

环形等离子体中电子温度梯度不稳定性的粒子模拟

用粒子模拟方法求解描述环形等离子体中电子温度梯度静电模的回旋动力学方程.方程采用圆磁通面的轴对称环形几何系统，考虑了有限拉摩半径、电子渡越频率k_∥v _∥以及环形漂移(曲率和磁场梯度)运动w_D(v²_⊥,v ²_∥,θ)的效应.简述了粒子模拟的基本方法.采用了四阶变步长积分格式，使计算省时、简便.讨论了模的基本特征 , 并且给出了临界梯度对电子温度与离子温度之 关键词： 电子温度梯度不稳定性 粒子模拟 变步长积分格式 临界梯度     

托卡马克等离子体中电子温度梯度不稳定性的粒子模拟编码

本文简述了环形等离子体中电子温度梯度不稳定性的动力学特征粒子模拟的数学方程。给出了计算程序框图以及输入数据变量说明等；计算方法部分和数值模拟结果可参阅文献。在编码中，我们采用四阶自动变步长积分方法。该方法通过每积分一步计算的误差估计公式来帮助编制自动调整积分步长。     

Geometric phase induced by a cyclically evolving squeezed vacuum reservoir

We propose a new way to generate an observable geometric phase by means of a completely incoherent phenomenon. We show how to imprint a geometric phase to a system by adiabatically manipulating the environment with which it interacts. As a specific scheme, we analyze a multilevel atom interacting with a broadband squeezed vacuum bosonic bath. As the squeezing parameters are smoothly changed in time along a closed loop, the ground state of the system acquires a geometric phase. We also propose a scheme to measure such a geometric phase by means of a suitable polarization detection.     

The Klein-Gordon and the Dirac Oscillators in a Noncommutative Space

We study the Dirac and the Klein-Gordon oscillators in a noncommutative space. It is shown that the Klein-Gordon oscillator in a noncommutative space has a similar behaviour to the dynamics of a particle in a commutative space and in a constant magnetic field. The Dirac oscillator in a noncommutative space has a similar equation to the equation of motion for a relativistic fermion in a commutative space and in a magnetic field, however a new exotic term appears, which implies that a charged fermion in a noncommutative space has an electric dipole moment.     

Maximum in vibrational frequency shift of a hydrogen molecule in solid hydrogen under pressure

Raman measurements on solid hydrogen show a maximum in the vibrational frequency of a H₂ molecule as a function of pressure, around 350 Kbar. We give an interpretation of this experimental data by considering a model in which a single H₂ molecule is immersed in a dielectric medium, and enclosed in a spheroidal box to simulate the effect of pressure. The maximum results from a balance between a decreasing equilibrium bond length of H₂ with pressure at low pressures and a term which reflects the pressure dependence of the dielectric constant. Our results are consistent with available calculations which give a much lower vibrational frequency at a much higher pressure, for a H₂ molecule embedded in a metallic medium.     

Effects of a magnetic field on a modulated phase

The effects of a magnetic field on a modulated phase are studied. A modulated phase is found to have two critical fields H₁ and H₂. For a large enough magnetic field, H₁ and H₂ can be approximated by a linear law. As a result, the minimum magnetic field needed to destroy a modulated phase is a constant. The minimum magnetic field also greatly depends on the order of a commensurate phase. A very high order commensurate phase and an incommensurate phase cannot survive a magnetic field. The behaviour of a magnetoelastic chain in a magnetic field can be described by a harmless devil's staircase. The inverse temperature is found to play a role similar to that of a special magnetic field. The deeper physics underlying these new phenomena is the breaking of the left-right symmetry of a phase diagram. As a result a controllable path to a modulated phase is found.     

Experimental demonstration of a technique to generate arbitrary quantum superposition states of a harmonically bound spin-1/2 particle

Using a single, harmonically trapped 9Be(+) ion, we experimentally demonstrate a technique for generation of arbitrary states of a two-level particle confined by a harmonic potential. Rather than engineering a single Hamiltonian that evolves the system to a desired final state, we implement a technique that applies a sequence of simple operations to synthesize the state.     

Lognormal Modes of Dielectric Optical Waveguides

It is shown that, at a critical point where the effective refractive index of a mode coincides with the bulk index of a cladding region, optical waveguide modes exhibiting a lognormal feature are supportable for a hyperlongrange refractive-index profile. As a typical example of waveguides that support lognormal modes a parabolic-index core surrounded by a depressed-index cladding is presented.     

Asymmetric universal entangling machine for qubits

We give a definition of a universal entangling machine that entangles a system in an unknown state to a specially prepared ancilla. We describe explicitly such a machine for one qubit; i.e., we show how a qubit in an a priori unknown state can be entangled to a four-level ancilla by means of a unitary transformation. As a result, a fixed state-independent amount of entanglement is generated in exchange for a fixed degradation of qubit state fidelity.     

Synthesis of magnetic systems producing field with maximal scalar characteristics

A method of synthesis of the magnetic systems (MSs) consisting of uniformly magnetized blocks is proposed. This method allows to synthesize MSs providing maximum value of any magnetic field scalar characteristic. In particular, it is possible to synthesize the MSs providing the maximum of a field projection on a given vector, a gradient of a field modulus and a gradient of a field energy on a given directing vector, a field magnitude, a magnetic flux through a given surface, a scalar product of a field or a force by a directing function given in some area of space, etc. The synthesized MSs provide maximal efficiency of permanent magnets utilization. The usage of the proposed method of MSs synthesis allows to change a procedure of projecting in principal, namely, to execute it according to the following scheme: (a) to choose the sizes, a form and a number of blocks of a system proceeding from technological (economical) reasons; (b) using the proposed synthesis method, to find an orientation of site magnetization providing maximum possible effect of magnet utilization in a system obtained in (a). Such approach considerably reduces a time of MSs projecting and guarantees maximal possible efficiency of magnets utilization. Besides it provides absolute assurance in “ideality” of a MS design and allows to obtain an exact estimate of the limit parameters of a field in a working area of a projected MS.The method is applicable to a system containing the components from soft magnetic material with linear magnetic properties.     

The development of a portable line-shaping optical system for silicon surface treatment

This study proposes a beam shaper for converting a circle beam profile generated with a Gaussian intensity distribution by an 808 nm diode laser into a line beam profile for silicon surface treatment applications. To produce a hand-held and low-cost device with a large spot-size laser, this study uses a portable optical system consisting of a diode laser source, a collimator, a cylindrical lens, and a plano-convex lens to generate an approximately 40 × 3:5mm² line beam profile at a working distance of 200 mm. The silicon surface treated by the line-shaped laser beam has significantly reduced reflectance spectra. The proposed system is also suitable for the surface cleaning of materials.     

Some non-abelian phase spaces in low dimensions

A non-abelian phase space, or a phase space of a Lie algebra, is a generalization of the usual (abelian) phase space of a vector space. It corresponds to a para-Kähler structure in geometry. Its structure can be interpreted in terms of left-symmetric algebras. In particular, a solution of an algebraic equation in a left-symmetric algebra which is an analogue of classical Yang–Baxter equation in a Lie algebra can induce a phase space. In this paper, we find that such phase spaces have a symplectically isomorphic property. We also give all such phase spaces in dimension 4 and some examples in dimension 6. These examples can be a guide for a further development.