Magnetic guiding of cold neutral atoms using a V-shaped current-carrying conductor

A new scheme to magnetically guide cold, neutral atoms using a V-shaped current-carrying conductor is proposed. The spatial distributions of the magnetic fields, potentials and forces generated by the V-shaped current-carrying conductor are calculated, and the relationship between the magnetic field and the parameters of the V-shaped current-carrying conductor are analyzed in detail. Our study shows that the V-shaped current-carrying conductor proposed here can be used to guide cold atoms in the weak-field-seeking state, and to construct various atom-optical elements, such as atomic funnel, atomic beam-splitter and atom interferometer and so on, and even to realize a single-mode atomic waveguiding under certain conditions. Received 17 November 2000 and Received in final form 26 May 2001     

Arrays of microscopic magnetic traps for cold atoms and their applications in atom optics

A single microscopic magnetic trap for neutral atoms using planar current-carrying wires was proposed and studied theoretically by Weinstein et al.In this paper,we propose three structures of composite current-carrying wires to provide 1D,2D and 3D arrays of microscopic magnetic traps for cold alkali atoms.The spatial distributions of magnetic fields generated by these structures are calculated and the field gradient and curvature in each single microtrap are analysed.Our study shows that arrays of microscopic magnetic traps can be used to provide 1D,2D or 3D atomic magnetic lattices,and even to realize 1D,2D and 3D arrays of magneto-optical traps,and so on.     

高频原子波导中冷原子的磁导引

建立了高频原子波导模型,分析了铷冷原子在该波导内与磁场的相互作用势。高频波导线圈输入电流,在线圈中心轴线区域的势阱深度为mK量级,在线圈的径向能对温度为100 K左右的冷原子实现囚禁。通过分析可知改变输入波导线圈的输入电流大小,可改变势场的大小。计算了进入高频原子波导的冷原子和波导磁场产生相互作用束缚力的大小。在波导轴线中心区域,原子受到的束缚力较大,最大为1.710－23 N,为原子所受重力的10倍。     

高频原子波导中冷原子的磁导引

建立了高频原子波导模型,分析了铷冷原子在该波导内与磁场的相互作用势。高频波导线圈输入电流,在线圈中心轴线区域的势阱深度为mK量级,在线圈的径向能对温度为100 K左右的冷原子实现囚禁。通过分析可知改变输入波导线圈的输入电流大小,可改变势场的大小。计算了进入高频原子波导的冷原子和波导磁场产生相互作用束缚力的大小。在波导轴线中心区域,原子受到的束缚力较大,最大为1.710－23 N,为原子所受重力的10倍。     

用转轮演示载流导线在磁场中的受力

介绍了用转轮方式演示载流导线在磁场中受力的原理和演示方法。     

电流连续的细导体段模型的磁场及电感

传统的载流细导体段模型是分析导体闭合回路磁场的基本模型,尽管不满足电流连续性定律,但适用于导体闭合回路的磁场分析.然而,对于工程中只关注导体闭合回路中某一局部的多分支导体段并联的电流分配问题,传统模型将不能完整地反映各分支导体段之间磁场的相互作用.为此,现有文献提出的位移电流模型,满足了电流连续性定律,较好地解决了上述问题,但是,仍然存在理论不完整、不自洽以及计算公式复杂等问题.本文提出载流细导体段的传导电流模型,确保了载流细导体段在段内、段端及段外的电流连续性.推导出物理内涵更加深刻的总磁场微分方程和矢量磁位计算公式.提出载流细导体段传导电流模型磁场能量和电感的计算公式,极大地降低了计算复杂度,弥补了现有文献的不足.本文算例从模型、公式、计算等方面验证了本文理论和计算公式的正确性.     

Reflection of cold atoms from an array of current-carrying wires

We report the realization of a new type of magnetostatic mirror for slowly moving atoms which comprises a planar array of parallel wires alternately carrying electric current in opposite directions. One of the features of this atomic mirror is that the magnetic field may be readily varied, switched or modulated by altering the current in the wires. Reflection signals close to 100% at a pulsed current of 3 A are demonstrated for a beam of free-falling laser-cooled cesium atoms at normal incidence. The current dependence of the reflection signals exhibits structure which is associated with the sequential onset of reflection of cesium 6² S _1/2 , F=4 atoms in the m=+4, +3, +2 and +1 magnetic states. Measurements of the spatial distribution of the reflected atoms indicate the reflection is predominantly specular at currents of 3 A. Received: 31 August 1998 / Accepted: 6 October 1998     

Propagation of cold atoms along a miniature magnetic guide

A cloud of laser-cooled 85Rb atoms is coupled through a magnetic funnel into a miniature waveguide formed by four current-carrying wires embedded in a silica fiber. The atom cloud has a approximately 100 &mgr;m radius within the fiber and propagates over cm distances. We study the coupling, propagation, and transverse distribution of atoms in the fiber, and find good agreement with theory. This prototype demonstrates the feasibility of miniature guides as a tool in the new field of integrated atom optics, leading to single-mode propagation of de Broglie waves and the possible preparation of 1D atom clouds.     

Magnetic focusing of cold atomic beam with a 2D array of current-carrying wires

A new scheme to realize a two-dimensional (2D) array of magnetic micro-lenses for a cold atomic beam,formed by an array of square current-carrying wires,is proposed.We calculate the spatial distributions of the magnetic fields from the array of current-carrying wires and the magnetic focusing potential for cold rubidium atoms,and study the dynamic focusing processes of cold atoms passing through the magnetic micro-lens array and its focusing properties by using Monte-Carlo simulations and trajectory tracing method.The result shows that the proposed micro-lens array can be used to focus effectively a cold atomic beam,even to load ultracold atoms or a BEC sample into a 2D optical lattice formed by blue detuned hollow beams.     

利用磁矢势计算分离均匀载流薄圆筒周围的磁场强度

根据一对反平行无限长载流直导线周围等磁矢势线的特点,与分离载流薄圆筒表面的等磁矢势线进行类比,采用等效替代法方便地得到分离载流薄圆筒周围的等磁矢势线函数与磁场强度函数.     

Magnetic interactions of cold atoms with anisotropic conductors

We analyze atom-surface magnetic interactions on atom chips where the magnetic trapping potentials are produced by current carrying wires made of electrically anisotropic materials. We discuss a theory for time dependent fluctuations of the magnetic potential, arising from thermal noise originating from the surface. It is shown that using materials with a large electrical anisotropy results in a considerable reduction of heating and decoherence rates of ultra-cold atoms trapped near the surface, of up to several orders of magnitude. The trap loss rate due to spin flips is expected to be significantly reduced upon cooling the surface to low temperatures. In addition, the electrical anisotropy significantly suppresses the amplitude of static spatial potential corrugations due to current scattering within imperfect wires. Also the shape of the corrugation pattern depends on the electrical anisotropy: the preferred angle of the scattered current wave fronts can be varied over a wide range. Materials, fabrication, and experimental issues are discussed, and specific candidate materials are suggested.     

磁体与非磁性运动导体相互作用之讨论

通过分析磁体与非磁性运动导体间的相互作用,发现了一种由非磁性运动导体驱动永磁体转动的非接触驱动方式.从分子环流模型出发,利用毕奥-萨伐尔定律,给出了所用矩形永磁体的磁场分布解析表达式,对运动导体处于永磁体下方5 mm处时永磁体的受力做了定量计算.对相互作用中的磁悬浮效应做了新的解释,澄清了PASCO公司对"磁悬浮实验装置"中由电磁感应产生的物理现象在原理解释上的模糊之处.     

导体和介质都存在时的镜象问题

讨论导体和介质界面同时存在时的镜象问题,指出了某些书中的一些问题,并作出了必要的修改．     

轴对称导体在均匀磁场中转动时的电荷分布及其电磁场的求解方法

指出了某些文献中的问题,根据电荷守恒定律,证明了由转动磁场所导致的电场E=±v×B的散度,并非与真实的电荷体密度有本质上的关联,而只是一种相对论效应.并根据电磁场变换原理,给出了轴对称导体在均匀稳恒磁场中转动时表面电荷密度及其电磁场的求解方法,得出了在均匀稳恒磁场中转动的导体球表面电荷密度及其电磁场.     

Fabrication of silver stabilization layer of coated conductor using organic silver complexes

Silver stabilizing layer of coated conductor has been prepared by dip coating method using organic silver complexes containing 10 wt.% silver as a starting material. Coated silver complex layer was dried in situ with hot air and converted to crystalline silver by post heat treatment in flowing oxygen atmosphere. A dense continuous silver layer with good surface coverage and proper thickness of 230 nm is obtained by multiple dip coatings and heat treatments. The film heat treated at 500 °C showed good mechanical adhesion and crystallographic property. The interface resistivity between superconducting YBCO layer and silver layer prepared by dip coating was measured as 0.67 × 10⁻¹³ Ω m².     

采用Damman光栅实现冷原子或冷分子囚禁的光阱阵列

提出了一种采用Damman光栅和球面透镜组合光学系统产生二维光阱阵列的新方案. 在使用红失谐高斯激光束照射的条件下，推导了计算光阱阵列的周期、光强分布、光强梯度和光阱几何参数的经验公式，讨论了此光阱阵列的特点以及在原子光学和分子光学中的应用. 研究结果表明，这种光阱阵列方案比已有的光阱阵列方案更为简单可行、操作方便，非常适用于冷原子或冷分子的阵列囚禁，以及制备新颖的光学晶格. 关键词： 冷原子或冷分子 光阱阵列 Damman光栅 光偶极势     

带电导体椭球的电势和电荷分布

介绍用椭球坐标系求带电导体椭球所产生的电势和它上面电荷分布的方法,并讨论一些特殊情况.     

反向导引场自由电子激光器的三维非线性模拟

 对Conde–Bekefi反向导引场自由电子激光（FEL）放大器实验进行了三维非线性分析。当引入一类似于回旋自谐振脉塞收缩角(pinch angle)参数的电子束入射角参数后，其模拟计算结果与实验相符。这预示了反向导引场FEL中束波互作用的一种新机理。     

求接地导体感应电荷的一种简便方法

由一道证明题引申出一个命题,对该命题给出了证明;通过几个实例说明应用该命题可以简便地求解某些接地导体的感应电荷.     

载流有限长密绕螺线管的磁场分布

对于通以恒定电流的有限长螺线管,首先用柱函数展开法推导出矢势的表达式,再利用磁感应强度与矢势的关系式,得出积分形式的磁场表达式.然后用直接积分的方法计算出磁场分布的级数表达式.最后讨论了某些特殊位置处的磁场.