Special-purpose radiation sources based on the Siberia-2 storage ring

Synchrotron radiation (SR) generated by homogeneous magnetic fields of bending magnets is now employed at the Siberia-2 electron storage ring. It is planned that, in the near future, most of the storage ring’s free straight sections will be equipped with insertion devices (undulators and wigglers). Two projects of specialized radiation sources based on the Siberia-2 stor age ring are discussed. The first source is a vacuum milliundulator intended for generation of extremely bright X-ray beams. An X-ray source with vertically limited diffraction is shown to be feasible when the vertical emittance of an electron beam is equal to the diffraction emittance of photons with an energy of 2 keV. The second source uses edge radiation (ER) generated at the ends of bending magnets of the storage ring. Calculations show that, in the infrared and ultraviolet spectral regions, the ER intensity must exceed the intensity of standard SR formed by the homogeneous field of a bending magnet.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility (SSRF)booster ring, a full energy injector for the storage ring, is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping. Closed orbit distortion (COD) caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting. Considering the affections of random errors in measurement, both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5 is given as the final installation sequence of the booster bending magnets in this paper.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

高功率激光在存储环上的应用

重离子冷却存储环中的束流是高密度的等离子体,这样的束流照射物体将得到超高压强．如果高功率激光照射束流,将产生实验室中从来没有过的超高温度．这些极端的条件为开辟重离子物理研家新领域提供了可能性．在存储环中使用X射线激光可以测显类锂离子的电荷均方根半径绝对值,使核基态性质的研究将有突破性的进展．它开辟了在等离子体物理、金属物理、核物理和天体物理等领域新的实验条件．为惯性聚变的快速点火创造了最好条件． In cooling storage ring heavy ion beam is plasma of high density. when a big power laser interacted on it, it will get ultra-high temperature. This beam irradiated on an object will get ultra-high pressure. This high energy pulse laser can produce X-ray laser. In the cooling storage ring absolute value of charge mean root radius of Lithium-like nuclei will be measured by the X-ray laser. It will be broken through in investigating the property of nuclear ground state. That will create many...     

Crystallized ion beams in a storage ring

Summary Crystallization for an ion beam in a storage ring was theoretically studied. Properties of ordered state of ion beams are discussed under smooth approximation. In particle simulations, performed in a realistic lattice, high-density three-dimension crystalline structures were achieved. In all cases the crystal had no shear slippage and only particle oscillations with the lattice periodicity took place. A linear dependence of longitudinal velocity on horizontal position, foreseen by the theory for ground states in a smooth lattice, was observed in all cases. This is a step forward in the understanding of crystalline ground states: the particles spontaneously organize themselves so to have the same angular velocity and to maintain their reciprocal position as in usual matter crystals. Theoretical considerations on shear and breathing are presented. The authors of this paper have agreed to not receive the proofs for correction.     

Evaluation of the LEP centre-of-mass energy above the W-pair production threshold

Knowledge of the centre-of-mass energy at LEP2 is of primary importance to set the absolute energy scale for the measurement of the W-boson mass. The beam energy above 80 GeV is derived from continuous measurements of the magnetic bending field by 16 NMR probes situated in a number of the LEP dipoles. The relationship between the fields measured by the probes and the beam energy is calibrated against precise measurements of the average beam energy between 41 and 55 GeV made using the resonant depolarisation technique. The linearity of the relationship is tested by comparing the fields measured by the probes with the total bending field measured by a flux loop. This test results in the largest contribution to the systematic uncertainty. Several further corrections are applied to derive the centre-of-mass energies at each interaction point. In addition, the centre-of-mass energy spread is evaluated. The beam energy has been determined with a precision of 25 MeV for the data taken in 1997, corresponding to a relative precision of . This is small in comparison to the present uncertainty on the W mass measurement at LEP. However, the ultimate statistical precision on the W mass with the full LEP2 data sample should be around 25 MeV, and a smaller uncertainty on the beam energy is desirable. Prospects for improvements are outlined. Received: 14 December 1998 / Published online: 3 November 1999     

Frontispiece: Photonic Floquet topological insulators in atomic ensembles

The feasibility of realizing a photonic Floquet topological insulator (PFTI) in an atomic ensemble is demonstrated by Yiqi Zhang et al. (pp. 331–338) . The interference of three coupling fields will split energy levels periodically, to form a periodic refractive index structure with honeycomb profile that can be adjusted by different frequency detunings and intensities of the coupling fields. This in turn will affect the appearance of Dirac cones in momentum space. When the honeycomb lattice sites are helically ordered along the propagation direction, gaps open at Dirac points, and one obtains a PFTI in an atomic vapor. An obliquely incident beam will be able to move along the zigzag edge of the lattice without scattering energy into the PFTI, due to the confinement of edge states. The appearance of Dirac cones and the formation of a photonic Floquet topological insulator can be shut down by the third‐order nonlinear susceptibility and opened up by the fifth‐order one.     

Calibration of centre-of-mass energies at LEP 2for a precise measurement of the W boson mass

The determination of the centre-of-mass energies for all LEP 2 running is presented. Accurate knowledge of these energies is of primary importance to set the absolute energy scale for the measurement of the W boson mass. The beam energy between 80 and 104 GeV is derived from continuous measurements of the magnetic bending field by 16 NMR probes situated in a number of the LEP dipoles. The relationship between the fields measured by the probes and the beam energy is defined in the NMR model, which is calibrated against precise measurements of the average beam energy between 41 and 61 GeV made using the resonant depolarisation technique. The validity of the NMR model is verified by three independent methods: the flux-loop, which is sensitive to the bending field of all the dipoles of LEP; the spectrometer, which determines the energy through measurements of the deflection of the beam in a magnet of known integrated field; and an analysis of the variation of the synchrotron tune with the total RF voltage. To obtain the centre-of-mass energies, corrections are then applied to account for sources of bending field external to the dipoles, and variations in the local beam energy at each interaction point. The relative error on the centre-of-mass energy determination for the majority of LEP 2 running is 1.2 x 10^-4, which is sufficiently precise so as not to introduce a dominant uncertainty on the W mass measurement. Received: 4 August 2004, Revised: 15 December 2004, Published online: 21 January 2005     

Beam life time studies and design optimization of the Ultra-low energy Storage Ring

The Ultra-low energy electrostatic Storage Ring (USR) at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) will provide cooled beams of antiprotons in the energy range between 300 keV down to 20 keV. Based on the original design concept developed in 2005, the USR has been completely redesigned over the past few years by the QUASAR Group. The ring structure is now based on a ’split achromat’ lattice. This ensures compact ring dimensions of 10 m × 10 m, whilst allowing both, in-ring experiments with gas jet targets and studies with extracted beams. In the USR, a wide range of beam parameters shall be provided, ranging from very short pulses in the nanosecond regime to a coasting beam. In addition, a combined fast and slow extraction scheme will be featured that allows for providing external experiments with cooled beams of different time structure. Detailed investigations into the dynamics of low energy beams, including studies into the long term beam dynamics and ion kinetics, beam life time, equilibrium momentum spread and equilibrium lateral spread during collisions with an internal target were carried out. This required the development of new simulation tools to further the understanding of beam storage with electrostatic fields. In addition, studies into beam diagnostics methods for the monitoring of ultra-low energy ions at beam intensities less than 10 ⁶ were carried out. This includes instrumentation for the early commissioning of the machine, as well as for later operation with antiprotons. In this paper, on overview of the technical design of the USR is given with emphasis on two of the most important operating modes, long term beam dynamics and the design of the beam diagnostics system.     

涡旋洛伦兹-高斯光束的远场矢量结构特征

利用矢量角谱法和稳相法,研究了涡旋洛伦兹-高斯光束的远场矢量结构特征,导出了横电项(TE项)和横磁项(TM项)远场电磁场和相应能流的解析表达式。通过相应的数值计算,分析了拓扑电荷数对涡旋洛伦兹-高斯光束及其矢量结构项远场能流分布的影响。TE项由位于竖直方向的2瓣或3瓣组成,TM项可由TE项旋转90得到。涡旋洛伦兹-高斯光束在拓扑电荷数小时内部中空,外部亮环均匀分布。增大拓扑电荷数,涡旋洛伦兹-高斯光束外部亮环上的能流呈起伏分布,内部变化相对复杂。涡旋洛伦兹-高斯光束及其矢量结构项的光斑尺寸随拓扑电荷数的增大而增大,但会饱和。研究显示,涡旋洛伦兹-高斯光束在实际应用时拓扑电荷数不宜过大。     

Phonons on surfaces: The importance of structure and adsorbates

Recent progress in detecting thermal energy vibrations at solid surfaces will be reviewed. Phonons on clean, well-ordered metals will be discussed as well as vibrations within ordered and disordered adlayers of adsorbed atoms and molecules. Simple lattice dynamical models will be used to demonstrate the interconnection between vibrations, structure, and force fields at a surface.     

五角棱镜角度误差对建立大尺寸平面基准的影响

用一准直光束作为基线，通过９０°折转的五角棱镜扫描，建立一个参考基准面在大尺寸测量中是一种行之有效的方法。在理想条件下，五角棱镜的折转角不受入射角的影响。由于有加工误差，光束的折转角将偏离９０°，且入射光线与扫描轴间的角运动也会影响该偏转角。本文分析了五角棱镜角度误差和扫描精度对光束折转角的影响。结果表明，五角棱镜的制造误差和工作状态将引起测量带误差，该误差是一个固定的系统误差，可以通过预先对所用的五角棱镜进行标定，在数据处理中予以修正。实验结果表明，修正后的结果具有很高的精度     

Systematical study of the trapping forces of optical tweezers formed by different types of optical ring beams

The technique of optical tweezers has been improved a lot since its invention, which extends the application fields of optical tweezers. Besides the conventionally used Gaussian beams, different types of ring beams have also been used to form optical tweezers for different purposes. The two typical kinds of ring beams used in optical tweezers are the hollow Gaussian beam and Laguerre--Gaussian (LG) beam. Both theoretical computation and experiments have shown that the axial trapping force is improved for the ring beams compared with the Gaussian beam, and hence the trapping stability is improved, although the transverse trapping forces of ring beams are smaller than that of Gaussian beam. However, no systematic study on the trapping forces of ring beam has ever been discussed. In this article, we will investigate the axial and transverse trapping forces of different types of ring beams with different parameters systematically, by numerical computation in which the ray optics model is adopted. The spherical aberration caused by the refractive index mismatch between oil and water is also considered in the article. The trapping forces for different objectives that obey the sine condition and tangent condition are also compared with each other. The result of systematical calculation will be useful for the applications of optical tweezers formed by different types of ring beams.     

基于旋转场曲率的二维剪切梁单元建模

对二维剪切梁单元进行研究,利用平面旋转场理论推导了精确曲率模型.采用几何精确梁理论构建了剪切梁单元弹性力矩阵.通过绝对节点坐标方法建立了系统的非线性动力学方程,提出基于旋转场曲率的二维剪切梁单元,并分别引入经典二维剪切梁单元和基于位移场曲率的二维剪切梁单元进行比较研究.首先,静力学分析证明了所提模型的正确性;其次,特征频率分析验证了模型可与理论解符合,收敛精度高,并且能准确地预测单元固有频率对应的振型;最后,在非线性动力学问题上,通过与ANSYS结果对比分析,证明了该模型可有效处理柔性大变形问题,并且与经典二维剪切梁单元相比具有缓解剪切闭锁的优势.因此,本文提出的基于旋转场曲率的二维剪切梁单元在处理几何非线性问题中具有较大的应用潜力.     

激光减速原子束频标的建议

本文提出一个激光减速的碱金属原子束频标的方案。用共振激光束对原子束同时进行减速和选态,使原子速率降到10m/s以下,而光抽运作用使原子自动集中到基态超精细结构中具有最大磁量子数的塞曼子能级上。为避免重力场中束轨迹下垂,用偏转磁铁或多束激光使束由水平转成垂直向上,然后用级联磁共振使原子过渡到频标所需的m_F=0能级。利用原子上升和重力场中自由下落两次通过单个微波谐振腔而取得Ramsey共振信号,线宽约为¹Hz。信号用另一束激光检测。予期这种频标的稳定度和准确度可比现有束型频标提高一个数量级以上。文中详细讨论了激光减速和选态的方法,克服横向加热效应的措施,实现级联磁共振的办法,以及获得垂直束装置的设计等。     

Boundary conditions for the bending of a piezoelectric beam

For beam bending in transversely isotropic piezoelectric media, the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the beam of general edge geometry and loadings. By generalizing the method developed by Gregory and Wan, a set of necessary conditions on the edge-data for the existence of a rapidly decaying solution is established. The prescribed edge-data of the beam must satisfy these conditions in order that they could generate a decaying state within the beam. When stress and mixed conditions are imposed on the beam edge, these decaying state conditions for the case of bending deformation of piezoelectric beam are derived explicitly. They are then used for the correct formulation of boundary conditions for the beam theory solution (or the interior solution). Besides, an analytical solution of elastic beam is formulated to verify validity of our boundary conditions. For the stress data, our boundary conditions coincide with those obtained in conventional forms of beam theories. More importantly, the appropriate boundary conditions with two sets of mixed edge-data are obtained for the first time.     

Ultrashort laser-pulse diagnostics for detection of ordering within an ion beam

A novel diagnostic method to detect ordering within one-dimensional ion beams in a storage ring is presented. The ions are simultaneously excited by a ultrashort pulsed laser ( 1 ps) at two different locations along the beam and fluorescence is detected by a group of four photomultipliers. Correlation in fluorescence signals is a firm indication that the ion beam has an ordered structure.     

高能光源增强器束流横向尺寸测量系统设计

高能同步辐射光源的增强器将直线加速器注入的束流加速到储存环所需的能量,为储存环提供高品质的电子束。为了对增强器的束流横向截面尺寸、发射度及能散进行测量,设计了两条可见光-紫外波段的束测光束线。两条光束线分别选取无色散和色散较大的两处弯铁位置作为光源点,使用两套同步光成像系统来监测光源点的束流截面尺寸,并计算束流发射度及能散。介绍了同步光引出真空室及光学成像系统,对影响成像质量的空间分辨率进行了分析,并针对升能过程中不同能量下束流光斑变化的测量进行了设计。     

Subwavelength beam manipulation via multiple-metal slits coupled by disk-shaped nanocavity

A novel plasmonic structure consisting of three nano-scaled slits coupled by nano-disk-shaped nanocavities is pro- posed to produce subwavelength focusing and beam bending at optical frequencies. The incident light passes through the metal slits in the form of surface plasmon polaritons （SPPs） ,and then scatters into radiation fields. Numerical simulations using finite-difference time-domain （FDTD） method show that the transmitted fields through the design example can gener- ate light focusing and deflection by altering the refractive index of the coupled nanocavity. The simulation results indicate that the focal spot is beyond the diffraction limit. Light impinges on the surface at an angle to the optical axis will add an extra planar phase front that interferes with the asymmetric phase front of the plasmonic lens, leading to a larger bending angle off the axial direction. The advantages of the proposed plasmonic lens are smaller device size and ease of fabrication. Such geometries offer the potential to be controlled by using nano-positior!i0g systems for applications in dynamic beam shaping and scanning on the nanoscale.     

Scaling Law for Lattice Design of a Storage Ring

This paper describes and demonstrates the scaling law in the lattice design of a storage ring.When the size of the storage ring are enlarged or reduced according to a scale,the operating point ν and the beam emittance ε will be invarible.But while the energy of the storage ring is changed,the emittance will vary with the energy square.