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The single vortex in the FFLO state
No full textIn this Letter, we study the generalized Ginzburg-Landau (GL) functional near the tricritical temperature, and obtain the vortex solution of the FFLO state. Furthermore, we investigate the structure of the vortex and find that the vortices shrink when the Zeeman effect is weaken or temperature is lowered. (C) 2010 Elsevier B.V. All rights reserved
Dynamics of strangeness production in heavy-ion collisions near threshold energies
No full textWithin the framework of the improved isospin-dependent quantum molecular dynamics (ImIQMD) model, the dynamics of strangeness (K-0,K-+, Lambda, and Sigma(-,0,+)) production in heavy-ion collisions near threshold energies is investigated systematically, with the strange particles considered to be produced mainly by inelastic collisions of baryon-baryon and pion-baryon. Collisions in the region of suprasaturation densities of the dense baryonic matter formed in heavy-ion collisions dominate the yields of strangeness production. Total multiplicities as functions of incident energies and collision centralities are calculated with the Skyrme parameter SLy6. The excitation function of strangeness production is analyzed and also compared with the KaoS data for K+ production in the reactions C-12 + C-12 and Au-197 + Au-197
Parton energy loss in heavy-ion collisions via direct-photon and charged-particle azimuthal correlations
No full textCharged-particle spectra associated with direct photon (gamma(dir)) and pi(0) are measured in p + p and Au + Au collisions at center-of-mass energy root(S)(NN) = 200 GeV with the STAR detector at the Relativistic Heavy Ion Collider. A shower-shape analysis is used to partially discriminate between gamma(dir) and pi(0). Assuming no associated charged particles in the gamma(dir) direction ( near side) and small contribution from fragmentation photons (gamma(frag)), the associated charged-particle yields opposite to gamma(dir) (away side) are extracted. In central Au + Au collisions, the charged-particle yields at midrapidity (vertical bar eta vertical bar < 1) and high transverse momentum (3 < (assoc)(PT) < 16 GeV/c) associated with gamma(dir) and pi(0) (vertical bar eta vertical bar < 0.9, 8 < (trig)(PT) < 16 GeV/c) are suppressed by a factor of 3-5 compared with p + p collisions. The observed suppression of the associated charged particles is similar for gamma(dir) and pi(0) and independent of the gamma(dir) energy within uncertainties. These measurements indicate that, in the kinematic range covered and within our current experimental uncertainties, the parton energy loss shows no sensitivity to the parton initial energy, path length, or color charge
Isocaling and the symmetry energy in the multifragmentation regime of heavy-ion collisions
No full textThe ratio of the symmetry energy coefficient to temperature, a(sym)/T, in Fermi energy heavy-ion collisions, was experimentally extracted as a function of the fragment atomic number using isoscaling parameters and the variance of the isotope distributions. The extracted values were compared to the results of calculations made with an antisymmetrized molecular dynamics (AMD) model employing a statistical decay code to account for deexcitation of excited primary fragments. The experimental values are in good agreement with the values calculated from the final ground-state products but are significantly different from those characterizing the yields of the primary AMD fragments
PRESENT STATUS OF THE RCNP CYCLOTRON FACILITY
No full textThe Research Center for Nuclear Physics (RCNP)<br />cyclotron cascade system has been operated to provide<br />high quality beams for various experiments in nuclear and<br />fundamental physics and applications. In order to increase<br />the research opportunities, the Azimuthally Varying Field<br />(AVF) cyclotron facility was upgraded recently. A flattopping<br />system and an 18-GHz superconducting Electron<br />Cyclotron Resonance (ECR) ion source were introduced<br />to improve the beam’s quality and intensity. A new beam<br />line was installed to diagnose the characteristics of the<br />beam to be injected into the ring cyclotron and to bypass<br />the ring cyclotron and directly transport low energy<br />beams from the AVF cyclotron to experimental halls. A<br />separator is equipped to provide RI beams produced by<br />fusion reactions at low energy and by projectile<br />fragmentations at high energy. A muon capture beam line<br />(MUSIC) was constructed in this spring Developments<br />have been continued to increase secondary beams as<br />white neutrons, ultra cold neutrons, muons and unstable<br />nucleri
FIRST BEAM ACCELERATION IN KOLKATA SUPERCONDUCTING CYCLOTRON AND ITS PRESENT STATUS
No full textVECC, Kolkata were integrated by May 2009. After
achieving the required vacuum and Dee voltage a series
of internal beam trials were started. The beam was
accelerated to full extraction radius on August 25th and
beam confirmed by neutron measurements.
The trials were not without difficulty and several
problems did crop up during the initial phase. With minor
modifications vacuum of the order of 10-7 mbar was
obtained. Major problems encountered were related to
obtaining sufficient Dee voltages primarily due to ceramic
insulator cracking at moderate power levels leading to
vacuum breakdown. Earlier the 14 GHz ECR ion source
was connected with 23 metre injection line without much
difficulty.
An analogue beam was also accelerated before taking a
shutdown for installation of extraction system and major
augmentation of cryogenic plant. Presently extraction of
the beam is being tried. It is planned to transport the beam
to already installed first experimental station.IMP;Chinese Academy of Science
低能He~(2+)与He原子碰撞转移电离出射电子能谱研究；Investigation on Electron Energy Spectra of Transfer Ionization Process in 70 and 100 keV He~(2+) Colliding on He
No full text利用反应显微成像谱仪对70和100keV He2+与He原子碰撞转移电离(TI)过程中不同出射角度的电子能谱进行了测量,观测到出射电子能谱具有如下分布特征:出射电子速度分布介于0和入射离子速度vp之间;在不同出射角度电子能谱分布均有一极大值存在,随着出射角度的增大,能谱分布极大值逐渐减小;当电子出射角度等于45°时,多数电子集中在0eV附近。上述特征可由低能离子-原子碰撞"准分子"模型进行定性解释。在100keV He2+-He转移电离出射电子能谱中有靶电子被俘获至散射离子连续态(electron capture to continuum,简称ECC)电子的贡献,这可看做是动力学两步过程的作用
兰州重离子治癌研究装置的准直测量技术；Survey and alignment for the heavy ion therapy facility at IMP
No full text介绍了中国科学院近代物理研究所重离子治癌装置的安装定位测量技术和方法。利用激光跟踪仪通过控制网的建立,和多重坐标系的转换,使最后的磁铁安装径向相对误差不超过±(0.05-0.1)mm,真空管道的横向及竖向精度也达到了±(0.1-0.2)mm
基于克隆选择算法的非线性优化迭代学习控制；Clonal selection algorithm based nonlinear optimal iterative learning control
No full text为实现对模型不确定的有约束非线性系统在特定时间域上输出轨迹的有效跟踪,将改进的克隆选择算法用于求解迭代学习控制中的优化问题。提出基于克隆选择算法的非线性优化迭代学习控制。在每次迭代运算后,一个克隆选择算法用于求解下次迭代运算中的最优输入,另一个克隆选择算法用于修正系统参考模型。仿真结果表明,该方法比GA-ILC具有更快的收敛速度,能够有效处理输入上的约束以及模型不确定问题,通过少数几次迭代学习就能取得满意的跟踪效果