An improved thermometer for intermediate-mass fragments

An improved thermometer (TIB) is proposed for intermediate-mass fragments via the difference between isobaric yield ratios. The residual free energy of three isobars is replaced by that of the binding energy. The measured fragments in the 140A MeV 40, 48Ca+ 9Be (181Ta) and 58, 64Ni+ 9Be (181Ta) reactions are analyzed to obtain TIB ranging from 0.6 to 3.5 MeV. TIB is suggested to be a direct determination of temperature avoiding the fit-ting procedure.     

Determination of neutron-skin thickness using configurational information entropy

Configurational information entropy （CIE） theory was employed to determine the neutron-skin thickness of neutron-rich calcium isotopes.The nuclear density distributions and fragment cross sections in 350 Me V/u^40-60Ca+⁹Be projectile fragmentation reactions were calculated using a modified statistical abrasion-ablation model.CIE quantities were determined from the nuclear density,isotopic,mass,and charge distributions.The linear correlations between the CIE determined using ...     

Temperature of intermediate mass fragments in simulated 40Ca + 40Ca reactions around the Fermi energies by AMD model

The primary fragments in ~(40)Ca +~(40)Ca reactions at 35,50,80,100,140,and 300 MeV/u were simulated using the antisymmetrized molecular dynamics model,in the phase space at t=300 fm/c with a coalescence radius R_c=5 fm.The standard Gogny interactions g0,g0 as,and gOass were adopted in simulating the collisions at an impact parameter of b=0 fm.It was found,using an isobaric yield ratio method,that temperature of the primary fragment depends on the incident energy and hardness of the interaction potential.The temperature obtained in this work agrees with the results by the self-consistent fitting method.     

A method for determination of the s orbital component of ~(12)Be ground state

The ambiguity of the structure of ~(12)Be especially in the configuration of Be ground state has attracted a lot of attention recently.We notice that the nuclear reaction cross section or at low energy region is sensitive to the surface structure of ~(12)Be,which is greatly impacted by the ground state configuration of ~(12)Be especially by the occupancy probability of the s orbital component.By using existed interaction cross section data of ~(12)Be on C at 790 MeV/nucleon and Glauber model,the upper limit of the s orbital occupation probability of ~(12)Be ground state is roughly determined to be about 56%with Single Particle Model calculations.This demonstrates that the method is very promising to determine the s orbital component of ~(12)Be with proper nuclear-matter density distribution calculations for different orbitals of ~(12)Be ground state.Hence we bring forward to determine the s orbital component of ~(12)Be by measuring the ctr of ~(12)Be on C and Al at several tens of MeV/nucleon.In this paper,the feasibility and detailed experimental scheme of the ctr measurement are carefully studied.The precision of the s orbital occupation probability of ~(12)Be ground state is expected to achieve 9%by using the proposed 2%ctr data.     

氘化闪烁体的光响应

在迴旋加速器上利用D(d,n)~3He反应和~9Be(d,n)~(10)B反应产生的中子,采用双参数方法测量NE-230和NE-232氘化闪烁体对氘以及国产的ST-451闪烁体对质子的光响应曲线,所测的实验值用二次多项式拟合。对其它性能也作了相对比较。     

Depth-profiling of beryllium on graphite with ion beams

The surface layer of beryllium-coated graphite was analysed by backscattering and nuclear reaction methods using a 2.5 MeV accelerator. For the Be analysis the nuclear reactions ⁹Be(p, d)⁸Be, ⁹Be(p, )⁶Li, ⁹Be(d, p)¹⁰Be, ⁹Be(d, t)⁸Be, ⁹Be(d, )⁷Li and ⁹Be(³He, p)¹¹B are compared with backscattering of ⁴He⁺ and protons. For the analysis of carbon, which provides complementary information to the depth profiling of Be, and for the analysis of oxygen, which is the third element of importance in the system, elastic backscattering of ⁴He⁺ and protons is applied. It turns out that the backscattering analysis with protons of 1.3 MeV presents the best compromise for a quick and straightforward measurement of all three elements. The other methods have their merits for a more detailed analysis.     

A data-based photonuclear simulation algorithm for determining specific activity of medical radioisotopes

For simulating more accurately neutron or proton production from photonuclear reactions,a data-based photonuclear reaction simulation algorithm has been developed.Reliable photonuclear cross sections from evaluated or experimental database are chosen as input data.For checking the validity of the use of the data-based photonuclear algorithm,benchmarking simulations are presented in detail.We calculate photonuclear cross sections or reaction yield for ~9Be,~(48)Ti,~(133)Cs,and ~(197)Au and compare them with experimental data in the region of incident photon energy below ~30 MeV.While Geant4 can hardly reproduce photonuclear experimental data,results obtained from the data-based photonuclear algorithm are found in good agreement with experimental measurements.Potential application in estimation of specific activity of radioisotopes is further discussed.We conclude that the developed data-based photonuclear algorithm is suitable for an accurate prediction of photoninduced neutron or proton productions.     

Excitation Functions Calculations of the Charged Particle-Induced Nuclear Reactions on the <Superscript>9</Superscript>Be Target

In this study, calculation of charged particles induced nuclear reactions of beryllium (⁹Be) target nuclei have been investigated in the incident proton and alpha at energy range from threshold to 50 MeV. The excitation functions for ⁹Be target nuclei reactions have been calculated by using PCROSS nuclear reaction calculation code. Weisskopf–Ewing model for equilibrium, calculations and the full exciton and cascade exciton models for pre-equilibrium calculations were used. Also, the semi-empirical calculations for (p,α) reactions have been done by using cross section formula updated with new coefficient developed by Tel et al. (Pramana Indian Acad Sci 74(6):931, 2010). The calculated results were compared with the experimental data for different energy levels ranging from 0.00 to 9.65 MeV taken from the literature.     

Feasibility of the application of statistical correlation techniques for the experimental study of the multiplication of 14 MeV neutrons in Be assemblies

The multiplication of 14 MeV neutrons through (n, 2n) reactions in Be and Pb, which are leading candidates for deployment as premultipliers in (D, T) fusion reactor blankets, is under active investigation in several laboratories. In the case of ⁹Be, since the secondary neutrons released in an (n, 2n) reaction could still carry enough energy to cause further generations of (n, 2n) reactions, a systematic study of the multiplicity distribution of the burst of neutrons leaking out of a finite-sized Be assembly, following deposition of a 14 MeV neutron in it, could yield very useful information on the physics of the (n, 2n) multiplicative process. Drawing from the wealth of experience available from previous studies in the field of reactor noise analysis and from the non-destructive assay of Pu content in sealed packages through measurement of the ²⁴⁰Pu spontaneous fission disintegration rate, as developed recently in the field of safeguards, a statistical correlation technique has been proposed for the study of (n, 2n) multiplication in Be (and Pb). The technique also appears to have potential applications for the study of the multiplicity distribution of neutrons produced in spallation targets.     

Evaluation of reactivity bonus due to (n, 2n) multiplication in Be/BeO-reflected 233U uranyl nitrate solution systems

Beryllium experiences (n, 2n) multiplication reaction for neutrons having energy above the threshold of ≈ 1.8 MeV. In the case of beryllium-reflected/moderated reactor assemblies these (n, 2n) neutrons contribute additional reactivity. This paper evaluates the reactivity contribution due to (n, 2n) reactions in the Be and BeO reflector of reflected ²³³U uranyl nitrate solution systems in spherical geometry in the light of the latest ⁹Be cross-section data. The results shows that the (n, 2n) reactions in a given thickness of reflector are directly proportional to the core leakage and thus very much a function of core radius. In the core radius range of 4–15 cm the reactivity bonus due to (n, 2n) reactions in a 30-cm thick Be reflector varies from 6.2 to 3.0%, which corresponds to a critical mass saving of ≈18–9%. The corresponding reactivity contributions for BeO reflected systems are ≈25% lower.     

用4.5MV静电加速器开展快中子照相的研究

用国产原材料研制了一种适用于快中子照相的关键部件——快中子转换屏。利用⁹Be(d，n)反应在北京大学4.5MV静电加速器上产生低于7MeV能区的快中子，采用胶片成像法进行了快中子照相的初步实验。借助带不同孔径的Fe等不同材料制作的不同厚度的试验样品，对快中子胶片成像法的基本性能进行了初步测试和研究。实验结果表明，研制的快中子转换屏能够满足快中子照相的需要。     

Measurements of thick-target (α, n) yields from light elements

High-precision measurements of thick-target yields from (α, n) reactions on Be, BeO, BN, C, UC, UO₂, Mg, Al, Si, Fe and stainless steel are described. The measurements cover an incident α-particle energy range of 3.6–10 MeV at energy intervals of 0.2 MeV in the energy range 4–7 MeV. The accuracy achieved is between 1 and 2% in most cases. As well as monitoring the incident α-particle energy by Rutherford scattering, precautions include a check for the presence of neutron-producing impurities in the targets by examination for γ-rays from (α, nγ), (α, pγ) and (α, α'γ) reactions.Values of the yields measured here from Be, Mg, Al and Si are 8–9% higher than recent published values. The measured yields in the compounds BeO and UC, when compared with those in Be and C, respectively, are used to assess a convenient approximate method of deriving thick-target yields in compounds from the values in the constituent elements.     

Silicon detector array for radioactive beam experiments at HIRFL-RIBLL

A new and innovative detector system based on a silicon strip detector dedicated to the study of the reaction induced by lighter radioactive beams is described herein.The detector system consists of five sets of three types of telescopes,which are successfully used to measure the angular distributions of both elastic scattering and breakup simultaneously, on the Radioactive Ion Beam Line in Lanzhou at Heavy Ion Research Facility in Lanzhou. This silicon detector array is used to measure the elastic scattering angular distributions of ~(11) Be on a ~(208) Pb target at E_(lab) = 140 and 209 MeV. A comparison of the Monte Carlo simulations with the experimental results shows a reasonable consistency.     

用金活化法测定加速器中子源中子注量及MCNP4C修正

在四川大学720所2.5MeV静电质子加速器上,由核反应7Li(p,n)7Be,T(p,n)3He产生中子,对中国工程物理研究院研制的新型中子探测器进行效率刻度实验中,需要知道探测器位置处的中子绝对注量,为此我们测量了0.165、0.352、0.576、1.400MeV四个能点的中子注量。测量方法采用的是金活化法,在实验测量中,由靶头材料、冷却水层和样品的包层材料等引起的多次散射效应及中子在样品中的自屏蔽效应等均对实验结果产生影响。这些因素在实验中不可避免,也难以通过实验方法扣除,因此用Monte Carlo程序MCNP4C对上述效应进行了修正计算。     

A function to provide neutron spectrum produced from the 9Be + p reaction with protons of energy below 12 MeV

A function to give the total neutron production cross section, angular distribution, and energy spectrum via the ⁹Be + p reaction has been created by fitting experimental data to characterize compact neutron sources with thick Be targets bombarded by protons with energy below 12 MeV. To examine the suitability of the function, calculations of the angle-dependent neutron energy spectra produced in thick Be targets with 4- and 12-MeV protons using the function were compared with corresponding experiments and calculations using the nuclear data libraries of ENDF/B-VII.0 and JENDL4.0/HE. The function was in better agreement with the experiments than the calculations using the libraries except for at backward angles. The ¹¹⁵In(n,n’)^115mIn reaction rates calculated using GEANT4 with source neutrons given by both the function and ENDF/B-VII.0 were compared with that measured at the RIKEN Accelerator-Driven Compact Neutron Source to evaluate the neutron spectrum above 1 MeV. The function slightly overestimated the measurement by 14% and the calculation with ENDF/B-VII.0 underestimated by 35%. It was concluded that the function can be applied in compact neutron source designs.     

放射性核束17N轰击9Be和197Au靶的中子发射

用飞行时间技术测得33.4MeV/u     

SUERC AMS ion detection

In a short time Be, C, Al, Cl, Ca and I accelerator mass spectrometry (AMS) have been established on the National Electrostatics Corporation (NEC) 5 MV pelletron system at the Scottish Universities Environmental Research Centre (SUERC). While summarising the present performance of the system, this report will focus on the details of ion detection, which sample materials are used and the analytical procedures employed for each individual species during routine analysis.All rare isotope detection is with a single flexible detector and ion event analysis system, but switching of analysed species typically requires a detector reconfiguration. Configurations for routine ¹⁰Be, ¹⁴C, ²⁶Al, ³⁶Cl, ⁴¹Ca and ¹²⁹I detection have been established and will be presented here. Notably, there has proven to be sufficient suppression of the isobaric interferences of ³⁶Cl and ⁴¹Ca in the 5+ charge state using an argon gas stripper at a terminal voltage of 5.0 MV to allow for routine analysis of these isotopes.     

8×8单元CsI(Tl)探测阵列研制

描述了1个8×8单元CsI(Tl)探测阵列的结构和工作原理。探测阵列的每个单元是由1块前表面21 mm×21 mm、后表面23.1 mm×23.1 mm、高50 mm的CsI(Tl)棱台、1块光导和光电倍增管组成。在兰州放射性次级束流线(RIBLL)上对探测阵列进行测试,得到探测阵列对30 MeV质子的能量分辨可达2.7%,对170 MeV7Be可达1.5%,可很好地用于放射性束物理实验中带电粒子的鉴别。     

An efficient method for mapping the ~(12)C+~(12)C molecular resonances at low energies

The ~(12)C+~(12)C fusion reaction is famous because of its complication of molecular resonances,and it plays an important role in both nuclear structural research and astrophysics. It is extremely difficult to measure the cross sections of ~(12)C+~(12)C fusions at energies of astrophysical relevance because of the very low reaction yields. To measure the complicated resonant structure that exists in this important reaction, an efficient thick target method has been developed and applied for the first time at energies E_(c.m.)5.3 MeV. A scan of the cross sections over a relatively wide range of energies can be carried out using only a single beam energy. The result of measurement at E_(c.m.)=4.1 MeV is compared with results from previous work.This method will be useful for searching for potentially existing resonances of ~(12)C+~(12)C in the energy range 1 MeVE_(c.m.)3 MeV.     

在HI-13串列加速器上利用逆几何反应产生次级放射性核束的可行性研究

论证了通过若干逆几何的(p,n),(d,p),(d,n)和(d,~3He)等低能重离子反应产生~6He,~7Be,~8Li,~(11)C,~(12)B,~(13)N,~(15)O和~(17)F等次级放射性核束的可行性,介绍了正在建造中的次级束实验装置的概貌。