Study of the lithium thiocyanate quadrupole by ultra-violet absorption spectroscopy

A spectroscopic method for studying quadrupole formation is described, and experimental results are presented for lithium thiocyanate in a tetrahydrofuran/hexane solvent system. From molar absorptivity equations and an equation by Fuoss and Kraus, a direct relationship is derived between the quadrupole formation constant, K_Q, and the dielectric constant of the medium. Experimental results are consistent with the equation and allow an estimate of the distance between lithium and thiocyanate in the ion pair.     

Design of a 10 MeV normal conducting CW proton linac based on equidistant multi-gap CH cavities

Continuous wave(CW) high current proton linacs have wide applications as the front end of high power proton machines. The low energy part of such a linac is the most difficult and there is currently no widely accepted solution. Based on the analysis of the focusing properties of the CW low energy proton linac, a 10 Me V low energy normal conducting proton linac based on equidistant seven-gap Cross-bar H-type(CH) cavities is proposed. The linac is composed of ten 7-gap CH cavities and the transverse focusing is maintained by quadrupole doublets located between the cavities. The total length of the linac is less than 6 meters and the average acceleration gradient is about1.2 Me V/m. The electromagnetic properties of the cavities are investigated by Microwave Studio. At the nominal acceleration gradient the maximum surface electric field in the cavities is less than 1.3 times the Kilpatrick limit,and the Ohmic loss of each cavity is less than 35 k W. Multi-particle beam dynamics simulations are performed with Tracewin code, and the results show that the beam dynamics of the linac are quite stable, the linac has the capability to accelerate up to 30 m A beam with acceptable dynamics behavior.     

Relativistic theory of the electric quadrupole moment of a hydrogen-like atom in the <Emphasis Type="Italic">s</Emphasis>1/2 and <Emphasis Type="Italic">p</Emphasis>1/2 states

Relativistic analytical expressions are derived for the electric quadrupole moment induced by the hyperfine interaction of the electron with the nucleus of a hydrogen-like atom in the ns_1/2 and np_1/2 states. The magnetic dipole and electric quadrupole hyperfine interactions are taken into account. The calculations are performed using the generalized virial relationships for the Dirac equation in a central field. The dependences of the electric quadrupole moment on the nuclear charge Z and the principal quantum number n are analyzed. The induced quadrupole moments are compared with the nuclear quadrupole moments.     

Geometrical Quantum Discord in the Coupled Cavities System with Tetrahedral Structure

In this paper we consider the situation that four identical two-level atoms are separately trapped in four single-mode optical cavities, which are placed at the vertices of a tetrahedron and coupled by six fibers. Each atom resonantly interacts with cavity via a one-photon hopping. The evolution of the state vector of the system is given by solving the schrödinger equation when the total excitation number of the system equals one. The geometrical quantum discords between atoms and between cavities are investigated. The effects of cavity-fiber coupling coefficient on the geometrical quantum discords between atoms and between cavities are discussed. The results obtained using the numerical method indicate that the geometrical quantum discords between atoms and between cavities are all weakened with increase of cavity-fiber coupling coefficient.

     

Constructing Robust Entangled Coherent GHZ and W States via a Cavity QED System

Using a system of three distant cavities, we propose a method for constructing tripartite entangled coherent GHZ and W states which are robust due to the photon losses in the cavities. Each of cavities is doped with a semiconductor quantum dot. By the dynamics, the excitonic modes of quantum dots are enabled to exhibit entangled coherent GHZ and W states. Apart from the exciton losses, the master equation approach shows that when the populations of the field modes in the cavities are negligible the destruction of entanglement due to dissipation arises from photon losses, is effectively suppressed.     

Geodesies in the Erez-Rosen space-time

We investigate null and time-like geodesics in the Erez-Rosen space-time, that is, in the exterior gravitational field of a mass with quadrupole moment. By using the weak-field approximation of the Erez-Rosen metric, we find the solution of the equation for equatorial time-like geodesics and determine how they differ from the corresponding Schwarzschild geodesies. For the exact form of the Erez-Rosen metric, we only draw some qualitative conclusions about the influence of the quadrupole moment on the path of test particles and on the motion of photons. We derive the relativistic contribution of the quadrupole moment to the perihelion shift and to the precession of the ascending node.     

Analysis on the frequency-domain numerical method to compute the noise radiated from rotating sources

A frequency-domain solution of the Ffowcs Williams-Hawkings equation with a penetrable data surface is presented for the thickness, loading and quadrupole noise to avoid the singularities that exist in the time-domain methods. Since this method is based on the numerical integration over source time, there is no need to solve the retarded-time equation or to perform the interpolation on time-domain data, and the time-domain source information obtained by modern CFD codes can be utilized directly. The acoustic pressure spectra of monopole, dipole and quadrupole point sources in subsonic and supersonic rotation are calculated with the presented method, and the results agree well with those obtained by the retarded-time method and frequency-domain analytical method.     

重入式谐振腔特性参数的解析方法

 对于在速调管中广泛使用的重入式谐振腔以及内部无漂移管的盒形腔,在忽略漂移管壁厚的前提下,导出了能够准确求解其谐振频率的本征方程,并在此基础上进一步计算了腔体的特性阻抗和固有品质因数。针对具体算例的应用表明,由解析式确定的腔体特性参数与SUPERFISH的数值结果具有很好的一致性。     

Theoretical investigation of unstable axial mass-selective extraction of ions from a nonlinear trap

The unstable axial mass-selective extraction of ions from a three-dimensional quadrupole ion trap is studied theoretically. A method for mapping the ion coordinates over the period of the RF power-supply voltage is developed with allowance for nonlinear distortions of the quadrupole potential. Equations for the envelope of ion oscillations are derived in the form of the equation of motion of a material point in the field of effective forces. The effect of the “delayed extraction” of ions in the presence of negative even field harmonics is explained. The positive even harmonics of the distorted quadrupole potential are shown to be favorable for ion extraction. The dynamics of the extracted ions is investigated.     

Nuclear scissors with pairing and continuity equation

The coupled dynamics of the isovector and isoscalar giant quadrupole resonances and low-lying modes (including scissors) is studied with the help of the Wigner-function-moment method generalized to take into account pair correlations. Equations of motion for collective variables are derived on the basis of the time-dependent Hartree-Fock-Bogoliubov equations in the harmonic-oscillator model with quadrupole—quadrupole residual interaction and a Gaussian pairing force. Special care is taken of the continuity equation. The text was submitted by the authors in English.     

Spin-dependent potentials in the linearized collective Schrödinger equation for nuclear quadrupole vibrations

The linearized collective Schrödinger equation for nuclear quadrupole surface vibrations incorporates a new spin degree of freedom with a spin value of 3/2. We use this equation to describe the low energy spectrum of certain even-odd Ir nuclei which have a spin 3/2 in their ground state. For that purpose we explicitly introduce collective spin-dependent potentials which simulate the interaction of the valence nucleon with the core. The linearized Schrödinger equation is transformed into an effective Schrödinger equation with collective spin-dependent potentials. Already collective spin-orbit couplings of SO(3) and SO(5) type are sufficient to reproduce the lowest excited states of even-odd Ir nuclei.     

New techniques in the theory of active mode-locking

A technique is presented that allows pulse profiles in the case of AM active mode-locking to be computed simply and essentially without approximation. Pulse shapes, pulse energies and pulse timings within the modulation cycle are all predicted. For cavities longer than the modulation period, the solutions are obtained from a simple two-point difference equation; for cavities that are shorter than the modulation period however, three-point difference equations apply, leading to a large tridiagonal system of linear equations. As in earlier work on mode-locking by synchronous pumping, steady-state pulses are predicted in the absence of a bandwidth-limiting filter, a feature that is at variance with the standard self-reproducing profile approaches to mode-locking problems.     

On classical hydrodynamics and collective motion as approximation to the nuclear many-body problem

Using time-dependent unitary transformations, one can cast a one-body equation of the time-dependent Hartree-Fock type into a form which is closely related to equations for a classical irrotational fluid. The hydrodynamic equation of state finds its counterpart in a stationary constrained field equation. The hydrodynamic equations in turn can be translated into a classical Hamiltonian formalism with an infinite number of generalised coordinates, which are given as all possible spatial moments of the density. The reduction to a few ones, the “natural collective coordinates” is possible by the choice of appropriate initial conditions. The lowest of the hydrodynamical frequencies can be calculated in closed form by harmonic approximations. For the quadrupole frequency a value ofω=31 A^?1/3 MeV/h is obtained. As expected, the value does not agree with the experiment, but rather is in between the characteristic frequency for theβ-vibration and the isoscalar giant quadrupole vibration.     

Bose-Einstein condensate in a random potential

An optical speckle potential is used to investigate the static and dynamic properties of a Bose-Einstein condensate in the presence of disorder. With small levels of disorder, stripes are observed in the expanded density profile and strong damping of dipole and quadrupole oscillations is seen. Uncorrelated frequency shifts of the two modes are measured and are explained using a sum-rules approach and by the numerical solution of the Gross-Pitaevskii equation.     

加速器驱动次临界系统注入器Ⅰ束测系统（英）

加速器驱动次临界系统注入器Ⅰ,包括ECR离子源、低能传输线、射频四极加速单元、中能传输段和超导腔,注入器Ⅰ出口能够获得能量10 MeV的强流质子束流。为了调束和运行的需要,注入器Ⅰ将安装束流位置测量、束流截面测量、束流流强测量、束流发射度和能量测量,以及束流损失测量等束流参数测量装置。介绍了这些束流测量系统设计及其他方面的一些考虑。     

Acoustic characteristics of annular cavities with locally non-uniform media

A theoretical approach is developed to obtain the natural frequencies and the mode shapes of annular cavities that have locally non-uniform media. The equation of motion is derived based on a special form of the wave equation that is capable of representing the variation of material properties with position, and the unit step function is used in the equation to express the local non-uniformity of the media. The Laplace transform is adopted in eigenvalue analysis to calculate the natural frequencies and the normal mode shapes of the annular cavities. The validity of the presented method is verified through finite element analysis and experiments. Parametric studies are performed to find out the relation between the acoustic characteristics of the cavity and the local deviation of the media, and the acoustic characteristics are explained in terms of the mass and stiffness effect of the local deviation in an annular cavity upon the natural vibration characteristics.     

Structural-acoustic coupling in complex shaped cavities

Structural-acoustic interaction is a topic of increasing interest in the study of vehicle noise control. During recent years particular attention has been devoted towards analytical and numerical methods for the analysis of acoustic problems of complex shaped cavities. Among them non-local methods are very appropriate for the low and medium frequency range. The integral formulation of the Helmholtz equation allows the sound pressure level, radiated by a vibrating panel, to be determined. The method may be used to account for the acoustic structural coupling and can be straightforwardly extended to consider interconnected cavities, internal vibrating panels, internal barriers and absorbing materials. Comparisons with experimental results as well as with modal methods are presented which show satisfactory agreement.