一台14.5GHz新型高磁场高电荷态ECR离子源

自行研制成功一台14.5GHz新型高磁场高电荷态电子回旋共振(ECR)离子源.描述了该离子源结构特点、参数优化及其磁场分布,并给出了调试测量结果.该离子源轴向磁镜场在轴线上的最高磁场可达1.5T,六极永磁体在弧腔内表面磁场可达1.0T.经初步调试,可得到0⁷+140eμA,Ar¹¹+185eμA,Xe²⁶⁺50eμA.所得结果与1998年国际上最好的ECR离子源进行了比较.     

RIBLL束流诊断

描述了兰州放射性离子次级束流线(RIBLL)上研制并安装使用的放射性束流(RIB)诊断装置的种类、结构、性能及在AIBLL上的位置和功能.重点叙述了以光纤为基础的几种诊断元件,它们探测效率高、响应时间快、制作容易、性能稳定.给出了RIB¹⁷N等高图,说明诊断装置辅助MBLL得到RIB的水平.     

周期场中强束流的特性研究

用薄透镜近似空间电荷相互作用的方法研究了强束流在周期场中的传输特性.通过计算可以说明束晕的形成.同时,也为研究比K–V分布更为复杂、真实的束流分布的传输特性提供了一种新的计算方法.     

Frictional cooling: Experimental results

The classical methods used in beam cooling are hard to be adapted for a beam of short-lived elementary particles. A novel method, the so-called frictional cooling – that is cooling a beam of low-energy charged particles by moderation in matter and acceleration in an electrostatic field – has been shown to be feasible. In our experiments performed in 1994/1995 a beam of short-lived particles was cooled for the first time ever. Utilizing frictional cooling on a beam of slow negative muons we observed increase in phase space density by about one order of magnitude. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of collimator size and absorber thickness on gamma ray attenuation measurements for bakelite and perspex

The mass attenuation coefficient (μ _m) of 662 keV gamma rays have been measured in the extended media of bakelite and perspex under different collimation conditions. The increase in attenuation coefficient is seen with increase in sample thickness as well as with collimator size due to the contribution of multiple scattered photons in the uncollided beam of 662 keV gamma rays.     

毫米波回旋速调管磁控注入电子枪模拟计算

介绍了毫米波回旋速调管磁控注入电子枪的结构与特点。电子枪提供的电子束流性能直接影响到回旋速调管的总体参数,为保证整管的效率和输出功率,利用电子枪模拟程序对电子轨迹进行模拟计算,研究了电极形状、磁场分布以及电子轨迹与电子注参量的影响,并为磁控注入电子枪的设计提供了理论依据。     

Fluorocarbon End-functionalized Polymers from Poly(arylether) Dendritic Initiators

Fréchet-type poly(arylether) first and second generation (G1 and G2 respectively) dendrons were prepared from 1-(bromomethyl)-3,5-bis(trifluoromethyl)benzene. The latter and the brominated versions of the two dendrons were successfully employed in the copper mediated living radical polymerization (LRP) of styrene-d₈ giving polymers of predictable molecular weights and narrow polydispersities. Contact angle measurements and ion beam analysis were used to explore the adsorption of these materials to the air-polymer surface in blended films with unfunctionalized hydrogenous polystyrene. Although contact angle analysis indicated only modest changes in the hydrophobicity and lipophobicity of the surface, ion beam analysis clearly showed the formation of an excess layer of dendron functionalized polymer at the exposed surface that increased with increasing fluorine content.     

Binary stopping theory for swift heavy ions

The Bohr theory treats charged-particle stopping as a sequence of interactions with classical target electrons bound harmonically to their equilibrium positions. We demonstrate that equivalent results can be derived on the assumption of free binary collisions governed by a suitable effective potential. This kind of mapping is rigorous in the limits of distant and close collisions and therefore provides a tool to evaluate energy losses via binary-scattering theory. This model was developed with the aim of calculating stopping forces for heavy ions at moderately high velocities, where a classical-orbital calculation is typically superior to the Born approximation. The effective potential employed holds equally well for dressed as for stripped ions. Unlike the Bohr theory, the present evaluation avoids a formal division into regimes of close and distant collisions that do not necessarily join smoothly. Moreover, no perturbation expansion is necessary. For these reasons the overall accuracy as well as the range of validity of the Bohr model are significantly enhanced. Extensive tests have been performed, including comparisons with rigorous evaluations of the Z ₁ ³ effect, with excellent agreement even where such was not necessarily expected. Moreover, credible results have been obtained under conditions where the perturbation expansion shows poor convergence. A comparison with experimental data on O–Al is encouraging, even though shell corrections and projectile excitation/ionization have not yet been incorporated and input has not yet been optimized. Received 21 April 2000 and Received in final form 16 June 2000 An erratum to this article is available at .     

Hydrogenated carbon clusters produced by highly charged ion impact on solid

The emission of small (hydrogenated) carbon cluster ions C_nHm ⁺ (n =2-22) upon highly charged Xe^q+ (q =20-44) impact on C₈₄ surfaces is studied by means of time-of-flight secondary ion mass spectrometry. The respective stage of hydrogenation/protonation of a certain carbon cluster ion Cn ⁺ is a strong indication for its geometrical structure. From the cluster ion yield as a function of cluster size it can be concluded, that the hydrogenation takes place after the initial carbon cluster formation. The carbon clusters seem to be emitted as an entity in agreement with “equilibrium” and “shock wave” models. Received 4 February 2000     

Lie-optics, geometrical phase and nonlinear dynamics of self-focusing and soliton evolution in a plasma

It is useful to state propagation laws for a self-focusing laser beam or a soliton in group-theoretical form to be called Lie-optical form for being able to predict self-focusing dynamics conveniently and amongst other things, the geometrical phase. It is shown that the propagation of the gaussian laser beam is governed by a rotation group in a non-absorbing medium and by the Lorentz group in an absorbing medium if the additional symmetry of paraxial propagation is imposed on the laser beam. This latter symmetry, however, needs care in its implementation because the electromagnetic wave of the laser sees a different refractive index profile than the laboratory observer in this approximation. It is explained how to estimate this non-Taylor paraxial power series approximation. The group theoretical laws so-stated are used to predict the geometrical or Berry phase of the laser beam by a technique developed by one of us elsewhere. The group-theoretical Lie-optic (or ABCD) laws are also useful in predicting the laser behavior in a more complex optical arrangement like in a laser cavity etc. The nonlinear dynamical consequences of these laws for long distance (or time) predictions are also dealt with. Ergodic dynamics of an ensemble of laser beams on the torus during absorptionless self-focusing is discussed in this context. From the point of view of new physics concepts, we introduce a stroboscopic invariant torus and a stroboscopic generating function in classical mechanics that is useful for long-distance predictions of absorptionless self-focusing.