采用双核模型研究超重核合成机制

本文首先介绍了两种描述低能重离子核反应的理论，然后基于这些理论发展了一个描述超重核合成的理论模型，即双核模型(dinuclear system model)。不同于Adamian 的处理，本文的模型采用数值求解主方程的方法来描述重离子的熔合过程，重点讨论了熔合过程中主方程的发展演化，选择一维至三维不同的宏观自由度说明重离子熔合机制，为今后进一步发展模型与预言新核素提供理论依据。     

Skyrme能量密度泛函在深度垒下熔合反应中的初步应用

基于Skyrme能量密度泛函并对动能密度按扩展的Thomas-Fermi半经典近似展开到四阶项,探索了深度垒下熔合反应的熔合截面急剧下降现象。通过分析熔合反应的入射道势和熔合截面来选择Skyrme参数,进而探索了深度垒下熔合反应与核物质状态方程之间的关系。     

Asymmetric barrier model for heavy ion fusion and its relation to channel coupling

A new asymmetric parabolic effective fusion barrier model for heavy ion fusion is developed.     

重离子惯性聚变的研究

本文描述了重离子惯性聚变的研究现状和用于重离子惯性聚变的重离子加速器． The present researching status and the heavy ion accelerators used for inertial fusion of heavy ions are decribed in the paper.     

An ion beam cooler for collinear laser spectroscopy

An ion beam cooler has been constructed and tested at the IGISOL mass separator facility at the University of Jyväskylä. The cooler is designed to improve the ion optical properties of radioactive ion beams produced with fission-, light-ion fusion and heavy ion fusion ion guides. The performance of the device has been tested in off- and on-line conditions. It has been shown that the emittance and energy spread of the ion beam can be decoupled from the ion guide parameters with high transmission efficiency.     

双核系统核子交换势能面

实验证实,用重离子碰撞合成超重原子核时,准裂变对熔合的抑制是非常重要的.碰撞中双核系统间核子转移所形成的势能面称之为驱动势,它制约核子转移,因而决定熔合与准裂变的竞争.双核系统势能面还提供重离子碰撞合成超重原子核的最佳激发能和最佳弹靶组合的信息.     

A massive-ion beam driver for high-energy-density physics and future inertial fusion

Several heavy ion drivers for heavy ion inertial fusion have been proposed in the US and Europe, based on linear induction accelerator technology [1] and existing RF technology [2], respectively, although they have not been realized on a large scale. Developing accelerator technology may provide an alternative efficient, robust, and relatively cheap massive-ion beam driver for future particle beam inertial fusion. Here, we propose an accelerator complex for accelerating giant cluster ions, instead of lead or bismuth ions, toward 120 GeV by using induction acceleration over the entire energy region. The proposed two-way multiplex induction synchrotron that is the main accelerator for the giant cluster ion beam would be equivalent to 10 synchrotrons of the same size for a single beam.     

Development of arc ion sources for heavy ion fusion

An overview of the development of arc ion sources for heavy ion fusion is presented. Two approaches to heavy ion fusion (HIF)-the RF linac-storage ring approach and the induction linac approach-are described. RF linac schemes require low emittance and moderate current levels, because the beam is accumulated in storage rings before being focused on target. The induction linac approach requires low emittance and high current, because this is a single-pass approach to HIF and one wishes to limit the number of beams in the machine. The RF scheme generally uses long pulse sources together with a buncher of RFQ. The induction linac approach requires sources in the microsecond pulse length range, with good optics being maintained during the pulse. Emphasis is on the induction linac approach pursued at the Lawrence Berkeley Laboratory     

Light ion fusion in deformation model

Experiments with heavy ions at moderate energies show the importance of deformation in heavy ion collisions. A deformation model which takes deformation dynamically into account is developed. Having described fusion and deep inelastic collision for a very heavy system (Xe + Bi) and a medium heavy system (Ar + Th) at various energies successfully, we turn to some comparatively lighter heavy ions where fusion is the most dominant feature. Fusion cross-sections for six pairs of lighter systems (³⁵Cl +¹¹⁶Sn,⁵⁸Ni+⁶²Ni,³⁵Cl+⁶²Ni,³²S+²⁴Mg,²⁴Mg+²⁴Mg and¹²C+²⁷Al) have been obtained using our deformation model which agree well with experiment. The two-slope-behaviour of fusion excitation function which is an important feature of light ion fusion systematics is also obtained, in our model calculations for all the systems studied.     

How well do we understand the synthesis of heavy elements by heavy-ion induced fusion?

Experimental cross sections to synthesize heavy ion induced fusion reactions are confronted with calculations using the conventional picture of complete fusion after passing the barrier plus statistical deexcitation after complete equilibration. The sensitivity of the calculations to some of the parameters is demonstrated. Despite this sensitivity, a single parameter set is found that reproduces well the large body of data from experiments using actinide targets. By comparison, for the more symmetric entrance channels using targets around²⁰⁸Pb, we find a fusion hindrance that increases steeply with increasing compound nuclear charge. Predictions for a few reactions of future interest for the synthesis of heavy elements are also presented.     

High energy γ-Rays from hot GDR: Recent developments

The high energy gamma decay of the GDR in rotating excited nuclei formed by heavy ion fusion reactions is studied.     

重离子熔合反应系统中的准裂变(英文)

在重离子熔合反应中,准裂变与熔合过程之间相互竞争。在双核模型中,常常在主方程中加入Kramers公式来描述准裂变。但只有当准裂变位垒足够高时,该公式才能成立。在本工作中,把弹靶核的间距作为独立的动力学变量,通过求解主方程来自洽地同时描述双核模型向全熔合和准裂变过程的演化,因此检验了Kramers 公式的适用条件。此外,在重离子熔合反应过程中,把动力学形变的演化和核子的转移过程都看成是耗散过程,在系统的势能面的约束下,同时求解含有动力学形变参量和质量不对称度参量的一系列主方程。研究显示了动力学形变对准裂变质量分布的直接影响,得到了与实验观测值符合得很好的计算结果。In heavy ion fusion reactions, the quasifission(QF) is competing with fusion, and which is often described by incorporating the Kramers formula(KRA-F) into the master equation(ME) within the Di-Nuclear System(DNS) model. However the KRA-F works well only if the QF barrier is high enough. Presently by takingthe relative distance of nuclei as an independent dynamical variable, the evolution of the DNS towards fusion and QF are both treated as a diffusion process in a consistent way by solving MEs. The validity of the KRA-F is thuschecked. Furthermore, the dynamical deformation and the nucleon transfer in heavy ion fusion reaction process are viewed simultaneously as a diffusion process, and are treated by solving a set of MEs with the variables of thequadrupole deformation of each nucleus and the mass asymmetry variable in the potential energy surface(PES) of the system. The distinct influence of the dynamical deformation on the QF mass yield distribution is discussed,and the experimental observations can be well reproduced by the calculation.     

Observation of the 3n evaporation channel in the complete hot-fusion reaction 26Mg + 248Cm leading to the new superheavy nuclide 271Hs

The analysis of a large body of heavy ion fusion reaction data with medium-heavy projectiles (6 < or = Z < or = 18) and actinide targets suggests a disappearance of the 3n exit channel with increasing atomic number of the projectile. Here, we report a measurement of the excitation function of the reaction (248)Cm ((26)Mg,xn)(274-x)Hs and the observation of the new nuclide (271)Hs produced in the 3n evaporation channel at a beam energy well below the Bass fusion barrier with a cross section comparable to the maxima of the 4n and 5n channels. This indicates the possible discovery of new neutron-rich transactinide nuclei using relatively light heavy ion beams of the most neutron-rich stable isotopes and actinide targets.     

Sub-barrier fusion excitation function data and energy dependent Woods–Saxon potential

This paper analyzed the role of intrinsic degrees of freedom of colliding nuclei in the enhancement of sub-barrier fusion cross-section data of various heavy ion fusion reactions. The influences of inelastic surface vibrations of colliding pairs are found to be dominant and their couplings result in the significantly larger fusion enhancement over the predictions of the one dimensional barrier penetration model at sub-barrier energies. The theoretical calculations are performed by using energy dependent Woods–Saxon potential model (EDWSP model) in conjunction with the one dimensional Wong formula. The effects of dominant intrinsic channels are entertained within framework of the coupled channel calculations obtained by using the code CCFULL. It is quite interesting to note that the energy dependence in Woods–Saxon potential simulates the effects of inelastic surface vibrational states of reactants wherein significantly larger value of diffuseness parameter ranging from a = 0.85fm to a = 0.95fm is required to address the observed fusion excitation function data of the various heavy ion fusion reactions.     

推广的液滴模型及其应用

简单介绍了近年来在研究重核和超重核衰变性质及熔合反应方面取得的理论成果和面临的挑战,着重阐述推广的液滴模型(GLDM) 理论框架及其应用。基于原子核的质量数、质子数以及反应Q 值,GLDM考虑了质量和电荷的不对称性、形状演化、亲近势和温度等,很好地描述了重核和超重核的质子放射性、 衰变、重离子放射性、自发裂变的半衰期和重离子熔合反应截面,同时也研究了原子核的粒子(质子、 、重离子) 放射性与自发裂变的竞争。Recent theoretical achievements and challenges about the fusion and decay properties of heavy and superheavy nuclei are generally introduced. Especially, the Generalized Liquid Drop Model(GLDM) as well as its application are emphatically described. Based on the mass number, proton number and the reaction Q value, the GLDM has taken the mass and charge asymmetry, the shape evolution, the proximity potential, as well as the temperature of nucleus into account, well described the proton radioactivity, the decay, the heavy particle radioactivity, the half life of spontaneous fission of heavy nuclei and superheavy nuclei, and the cross-sections of heavy ion fusion. The competitions between the spontaneous fission and other decay modes such as proton and heavy particle radioactivity, the alpha decay, and so on are also studied.     

HI－13串列加速器上的核反应研究及进展

本文简介了ＨＩ－１３串列加速器上开展的核反应及其进展情况,重离子垒下熔合反应、重离子准弹性碰撞和轻粒子核反应． The experimental studies and achievements recently made at the HI-13 tandem accelerator are reviewed,including many subjects of three research fields: sub-barrier fusion reaction, heavy ion quasielastic collision and light particle nuclear reaction.     

Radion and Higgs signals in peripheral heavy ion collisions at the LHC

We investigate the sensitivity of the heavy ion mode of the LHC to Higgs boson and Radion production via photon–photon fusion through the analysis of the processes γγ→γγ, , and γγ→gg in peripheral heavy ion collisions. We suggest cuts to improve the Higgs and Radion signal over standard model background ratio and determine the capability of LHC to detect these particles production.