40MeV/u 40Ar与Cu相互作用的靶余核

使用离线y能谱法和厚靶──厚收集箔技术测量了40MeV/u ⁴⁰Ar和Cu相互作用中靶余核的生成截面和前向平均反冲射程FW值.根据电荷分布假设得到了靶余核的质量产额分布.从FW值导出了重离子碰撞中的线性动量转移.与¹²C+Cu和²⁰Ne+Cu的类似结果比较指出,在相同的弹核速度下,相应于中心碰撞的相对线性动量转移随弹核质量增加而减小,但是在⁴⁰Ar离子和Cu的中心碰撞中产生的复合系统的激发能比¹²C和²⁰Ne离子碰撞情况下更高,达到每核子5.3MeV.     

42MeV/u 12C与115In相互作用的靶余核

使用放射化学方法测定了42MeV/u ¹²C与¹¹⁵In相互作用靶余核的生成截面,得到了质量分布及同位素分布.实验得到的质量分布与使用级联的两体衰变模型GEMINI程序计算的结果很好地相符.根据同位素分布的系统性,对利用中能重离子反应生成新的远离β稳定线的缺中子核素进行了讨论.     

45MeV/A 12C和181Ta相互作用中余核的研究

用厚靶-厚收集箔技术测量了45MeV/A ¹²C和¹⁸¹Ta相互作用中余核的生成截面和反冲性质,并将实验得到的质量产额分布与统计碎裂模型进行了比较.根据前向平均反冲射程计算了线性动量转移,在与我们以前工作相比较后指出,在45MeV/A ¹²C离子引起的反应中,中心碰撞的线性动量转移随靶质量而增加,并与引导粒子模型计算结果很好相符.     

20—46MeV/u 12C离子和Cu相互作用中靶余核的反冲性质研究

使用离线γ能谱法和厚靶-厚收集箔技术测量了20—46MeV/u ¹²C离子和铜相互作用中余核的前向平均反冲射程.导出了中心碰撞的线性动量转移.当轰击能量为27.5MeV/u时,每个入射核子转移的线性动量达到155MeV/c的最大值.复合系统的最大激发能为每核子2.5MeV.     

20MeV到180MeV/u 16O+197Au系统的BUU计算:线动量与角动量转移依赖碰撞参数与能量研究

用考虑了角动量守恒的BUU模型计算了20MeV≤E/u≤180MeV能区¹⁶O+¹⁹⁷Au系统的反应线性动量转移(LMT)及余核角动量,着重讨论了反应线性动量转移及余核角动量对反应碰撞参量、入射能E/u的依赖关系,比较了计算LMT与Viola系统性给出的结果间的偏差.计算结果揭示了当E/u≥90MeV时,余核角动量对E/u增长出现的饱和现象,主要来源于靶核对弹核捕获能力的持续丢失.     

44MeV/A12C离子与铜相互作用中靶余核的研究

在44MeV/A的¹²C离子和铜的相互作用中,用核化学技术测定了35个靶余核的截面以及前向平均射程.得到了同量异位素分布、质量分布和径向动量转移.质量分布和同量异位素分布与推广的统计模型和蒙特卡罗方法计算结果满意地相符.     

12N直接碎裂反应研究

描述了在兰州放射性束流线(RIBLL)上用78.6MeV/u的¹⁴N束流轰击Be靶产生出34.9MeV/u的¹²N次级束流. 利用¹²N轰击Si靶作为次级靶, 利用直接碎裂反应测量它的反应总截面. 利用理论模型进行了计算, 理论计算和实验结果符合的很好. 发现¹²N的质子密度分布相对于中子而言, 有一个很大的弥散.     

46.7MeV/u 12C轰击197Au、115In、58Ni靶时产生的复杂碎片

用气体电离室-半导体位置灵敏探测器望远镜测量了46.7MeV/u ¹²C离子轰击¹⁹⁷Au,¹¹⁵In,⁵⁸Ni靶时,在大角区发射的从Li到Mg的复杂碎片能谱;由各碎片的能谱提取了蒸发源的温度和碎片发射的最可几动能Ep,并与=V_coul+2T计算的平均动能进行了比较,发现实验上提取的最可几动能E_p总是低于计算的.用A.Friedman简单的统计公式对复杂碎片的产额进行粗糙拟合,拟合结果令人满意.     

600MeV 18O+natPb(厚靶)系统生成Hg同位素独立产额测量(Ⅱ)结果与分析

报道了600MeV ¹⁸O轰击^natPh(厚靶)生成的质量数在180—209之间的Hg同位素产物独立截面的测量结果.通过与600MeV质子轰击天然铅靶生成Hg同位素产额分布的比较,讨论了几个质量区段Hg同位素的生成机制.测量结果也与相对论重离子碎裂反应双质子移出道的产额分布进行了比较.结果表明,中能重离子与中子较富集靶核组成的反应系统对生成丰中子类靶余核具有较明显的优势.     

6.3—24.6MeV/u 40Ar+natW反应中Hf的生成研究

用放射化学方法研究了6.3—24.6MeV/u ⁴⁰Ar+^natW反应中Hf的生成,得到了Hf同位素的激发函数、反冲性质和同位素分布.指出利用HIRFL能量的重离子和丰中子靶核作用,能以一定的截面生成A>170区丰中子新核素.利用中能重离子的强穿透力特点,使用厚靶,可以明显地提高丰中子新核素的产额.过高的入射能量对新核素生成无明显贡献.     

Mass Yield Distribution of Target Residues from the Interaction of Iron with 135MeV/u 12C Ions

The formation cross sections of target residues have been measured from the interaction of iron with 135MeV/u ¹²C ions.With the help of assumption of Gaussian charge distribution,the mass yield distribution was obtained.We found that the yield in mass region of A＜30 were notably increased and the products got away to neutron-excessive.The experimental results were compared with calculations based on the statistical fusion fragmentation model and on the sequential binary decay model,respectively. It seems to indicate that the multifragmentation decay mode was the dominant reaction mechanism responsible for production of the fragments with mass number A＜30 in the produce process of target residues under the condition of the higher incident projectile energy.     

STUDY ON TARGET RESIDUES FROM THE INTERACTION OF COPPER WITH 44MeV/A12C IONS

Cross sections and average forward ranges were determined for 35 target residues from the interaction of copper with 44MeV/A¹²C ions with nuclear chemistry techniques.From these data the isobaric yield distribution,the mass yield distribution and the longitudinal momentum transfer were obtained.The mass yield distribution and the isobaric yield distribution are in good agreement with those calculated from a modified statistical model and corresponding Monte Carlo technique.     

Target Residues from the Interaction of Indium with 42MeV/nucleon 12C Ions

The cross section is measured for 65 target residues produced from the interaction of indium with 42MeV/nucleon ¹²C ions using nuclear chemistry techniques.The experimental mass yield distribution gives a satisfactory agreement with that calculated from Monte Carlo code GEMINI based on the statistical binary decay model. According to the systematics of isotope distributions,the possibility of the production of new neutron-deficient nuclides far from β stability is discussed in the intermediate energy heavy ion reaction.     

Exotic decay: Transition from cluster mode to fission mode

Exotic decay of some heavy nuclei with Z≥100 formed in heavy ion ‘cold fusion’ reaction were studied taking interacting barrier consisting of Coulomb and proximity potential. Calculated half-life time shows that some modes of decay are well within the present upper limit for measurements (T _1/2<10³⁰ s). Cluster formation probabilities are calculated for different clusters within fission model. It is found that transition from cluster mode to fission mode take place at mass of the cluster, A ₂=20 in exotic decay which is comparable with the value A ₂=16 of Shanmugam et al based on cubic plus Yukawa plus exponential model (CYEM).     

Complete and Incomplete Fusion in the Reaction of 65Cu With 16O Ions

The excitation functions,angular distributions and differential range distributions have been measured for target residues from the reaction of ⁶⁵Cu induced by 45—96MeV ¹⁶O ions with radiochemical techniques.A comparison of the experimental data with Monte-Carlo simulations based on the statistcal model of compound nucleus that the heavy residues are produced by the decay of a compound nucleus formed by complete fusion.Incomplete fusion or massive transfer are the main reaction mechnisms leading to production of the residues with mass number close to that of the target.     

Cross sections and dynamical properties of a emitters produced in interactions of 12C at 86 MeV/n on medium and heavy targets

Cross sections, mean recoil ranges and angular distributions of radioactive a emitters produced in ¹²C, induced reactions at 1 GeV on medium and heavy targets are presented. A new on-line electrostatic collection device is used. A wide spectrum of heavy residues corresponding to various mass losses away from the target between D to 60 a.m.u. has been observed. A phenomenological analysis based on the statistical decay of possible precursors gives some information on the properties of the primary interaction. Losses of 10 to 30 nucleons can be partly fitted by the intranuclear cascade model. For greater mass losses, more collective primary interaction is needed. The abrasion-ablation model can produce such residues but in its clean cuts approximation the predicted excitation energy is too low.     

Production of medium-weight isotopes by fragmentation in 750 A MeV 238U on 208Pb collisions

Projectile fragmentation of ²³⁸U in a lead target was investigated at a bombarding energy of 750 A MeV. Isotopic production cross sections of about 250 different projectile fragments in the element range Z= 30–53 were measured with the FRagment Separator (FRS). The magnetic selection and the kinematical analysis of the measured isotopes allowed to disentangle fission and fragmentation residues. The mass loss of these residues indicates a violent collision where a large amount of energy is dissipated. The position of the fragmentation corridor defined by the measured residues was used to determine an effective proton-evaporation barrier. Received: 3 October 1997 / Revised version: 27 February 1998     

Multiplicity and pseudorapidity distributions of charged particles from32S induced heavy ion interactions at 200A GeV

Multiplicity and pseudorapidity distributions have been measured for³²S+Al, Cu, Ag and Au at 200A GeV. The widths of the pseudorapidity distributions increase from central to peripheral collisions. The main contribution is assumed to come from the increasing fraction of charged particles stemming from the fragmentation of the target for peripheral collisions as compared to central collisions. On the average 170–180 charged particles per unit of pseudorapidity are attained for the most central³²S+Au events at the maximum of the distribution. The target dependence of the yield of charged particles for central collisions is investigated. In the target rapidity region the yield is directly proportional to the target mass. The transverse energy per charged particle has been studied as a function of centrality and pseudorapidity. The experimental results are compared to the results from the Monte-Carlo model VENUS 3.11 which includes rescattering among secondaries. A comparison between different centrality triggers is made.     

46.7MeV/u 12C轰击159Tb、197Au和209Bi的裂变测量及分析

用46.7MeV/u~(12)C轰击~(159)Tb、~(197)Au、~(209)Bi,测量关联裂片的速度和角度,研究了线性动量转移(LMT)、质量和出平面角分布,提取了核温度,应用级联两体统计衰变理论进行了拟合与解释,结果表明:在～50MeV/u入射能的中能重离子碰撞中,以非完全熔合方式形成了核温度高达4～5MeV的类复合核,其后通过裂变、蒸发级联统计两体衰变而退激。 The velocities and angles of fission partners emitted from reactions in ~(12)C+~(159)Tb, ~(197)Au,~(209)Bi systems with bombarding energy of 46.7MeV/u are measured. The linear momentum transferfrom projectile to target、mass and out-of-reaction plane angle distributions of fission fragments arestudied, and the temperatures of the target residues are extracted. These results have been explained by statistical binary decay model. It seems that the compound-likesystem with high temperature...