Total Fragmentation Cross Section of 158A GeV Lead Projectiles in Cu Target

Total fragmentation cross section for the reaction 158A Pb ions ＋ Cu target is measured using the most sensitive track detector CR-39. Measured values are compared with calculations. Exposures of target-detector stack with 158A P5 projectiles are made at CERN-SPS beam facility. Results of calibration of CR-39 detector in a charge region （63 ≤ Z ≤ 83） are also reported, which can be used for high energy particle identification using CR-39 and in determination of partial charge changing cross sections. The charge resolution δz achieved by this technique is about 0.2e. A systematic dependence of total fragmentation cross section on target properties is revealed and the corresponding results are presented.     

中高能重离子弹核碎裂反应研究

通过CR-39 核径迹探测器对471 AMeV 56Fe 和400 AMeV 20Ne 诱发Al,C 和CH₂ 靶反应的弹核碎裂反应截面及出射角度进行了测量,并利用改进的量子分子动力学(ImQMD) 模型和描述统计衰变的GEMINI 模型对实验结果进行了分析和讨论。实验结果表明,总反应截面与弹核的能量无关,但随着靶核质量的增加而增加。这与其他的实验结果以及Bradt-Peters 的半经验理论公式所得结果一致。理论计算和实验测量结果中,分截面出现了明显的奇偶效应。理论计算结果表明,奇偶效应主要产生于受激碎块的衰变过程,其中对效应起着重要作用,而且,主要形成于擦边碰撞的反应中且多来自于同位旋为T_Z = 0; ±0:5 的弹核碎块的贡献。产生碎块的同位素分布与弹核的种类有关,与入射能量和靶核的种类没有太大依赖性,其较小的偏转角大部分来自于擦边碰撞产生的较重的类弹碎块的贡献。We have measured the fragmentation cross sections and the emission angles for 471 AMeV 56Fe and 400AMeV 20Ne on Al, C and CH₂ targets using CR-39 plastic nuclear track detector. The total charge changing cross sections agree well with other previous experimental results at different energies and the theoretical prediction of Bradt-Peters semiempirical formula, which are pproximately independent of the beam energy but increase with the increase of the target mass. The experimental results are compared with the prediction of the improved quantum molecular dynamical model (ImQMD) together with the GEMINI model. The odd-even effect of the partial cross sections observed in experiments is well produced. It is found that such effect is mainly formed in the grazing collisions and comes from the fragments with T_Z = 0; ±0:5. The shape of the isotopic distribution is independent on the target mass and the incident energy but the projectile mass and charge, and the small angular distribution of all fragments comes from the heavier projectile-like fragments which produced in the peripheral collision.     

Charge-Changing Cross Sections of 736 A MeV ~(28)Si on Carbon Targets

The total and partial charge-changing cross sections of ~(28) Si on carbon targets at 736 and 723 AMeV are studied by CR-39 plastic nuclear track detectors using the HSP-1000 microscope system and the PitFit track measurement software. The values of the total charge-changing cross section are σ_((tot)) =(1179±50) mb and σ_((tot))t =(1186 ±42) inb at 736 and 723 A MeV, respectively. The result is compared with the ones obtained by other experimental and theoretical results. The odd-even effect of the partial charge-changing cross section is observed.     

一个奇异核反应总截面的探测系统及其应用

评述了现有的奇异核反应总截面测量方法,介绍了一套简单可行的测量中能区奇异核反应总截面的探测装置,并对实验的能量刻度、粒子鉴别以及实验结果进行了阐述和讨论． The present status of experimental studies of the total reaction cross sections of exotic nuclei are reviewed. A detector system used for measuring the total reaction cross section of radioactive ions is described. The energy calibration of detectors, particle identification and possible experimental results are discussed.     

几百兆电子伏特/核子能区原子核诱发乳胶核反应靶核蒸发碎片前后发射研究（英文）

对150 AMeV 4He-AgBr,290 AMeV 12C-AgBr,400 AMeV 12C-AgBr,400 AMeV 20Ne-AgBr及500 AMeV 56Fe-AgBr作用靶核蒸发碎片在反应前后半球内的多重数分布、多重数矩、标度方差、熵及约化熵分别进行了分析。实验结果表明,靶核蒸发碎片在前后半球内的多重数分布可以用高斯分布来描述。在前后半球内的多重数分布矩分别随秩数的增加而增加,且前后半球内多重数分布二阶矩与反应类型及束流能量无关。对于所有研究的核反应,其标度方差（一个直接描述多重数涨落的变量）值接近于1,表明在前后半球内靶核蒸发的发射存在较弱的关联。在前后半球内靶核蒸发碎片发射过程中的熵及约化熵在实验误差范围内与反应系统无关。The multiplicity distribution,multiplicity moment,scaled variance,entropy and reduced entropy of target evaporated fragments emitted in forward and backward hemispheres in 150 AMeV 4He-AgBr,290 AMeV 12C-AgBr,400 AMeV 12C-AgBr,400 AMeV 20Ne-AgBr and 500 AMeV 56Fe-AgBr interactions are investigated.It is found that the multiplicity distribution of target evaporated fragments emitted in both forward and backward hemispheres can be fitted by a Gaussian distribution.The multiplicity moments of target evaporated particles emitted in the forward and backward hemispheres increase with the order of the moment q,and the second-order multiplicity moment is energy independent over the entire energy range for all the interactions in the forward and backward hemisphere.The scaled variance,a direct measure of multiplicity fluctuations,is close to one for all the interactions,which indicate a weak correlation among the target evaporated fragments.The entropy of target evaporated fragments emitted in forward and backward hemispheres are the same respectively for all of the interactions,within experimental errors.     

The fragmentation of 20Ne at 400 A MeV

The total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV ²⁰Ne with aluminum, carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors. The measured total charge-changing cross sections are compared with the predictions using the Bradt-Peters semi-empirical formula, and the NUCFRAG2 and PHITS models. It is shown that the measured experimental results are in good agreement with the theoretical model prediction and other experimental results, and it can be clearly seen that the partial cross sections for fragment production show obvious odd-even effects.     

Electron impact excitation of helium atom

A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation(FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method,the convergent e–He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method.     

Cross Section of Heavy Ion Reaction （14.5 MeV/u） ^132Xe ＋ Bi

We investigate the cross section of the heavy ion reaction （14.5 MeV/u） ^132Xe ＋ Bi by using a CR-39 plastic track detector. The target-detector assembly is exposed at UNILAC beam facility of GSI, Germany. After etching under appropriate etching conditions, the detector is scanned for multipronged events produced as a result of interactions of projectile ions with target atoms. The elastic events are separated from binary events and used for the determination of the quarter-point angle. The quarter-point angle obtained is used to determine the total reaction cross section. The total experimental reaction cross section is determined by using statistics of inelastic events of two-pronged and higher multiplicity events. The experimental reaction cross sections determined by using elastic and inelastic data observed in the reaction under study are found to be in good agreement with the theoretically calculated value of reaction cross section using a sharp cutoff model.     

Multiple ionization of argon accompanied by electron loss and capture of 0.22-6.35 MeV C^q＋ ions

In this paper a projectile ions recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22-6.35 MeV Cq^＋ （q = 1 - 4） ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization （or the single capture） of argon associated with single electron loss （or single electron capture） by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.     

放射性核束引起的奇异核反应研究

结合开展的工作，对放射性核束流引起的核反应总截面研究、放射性束流引起的熔合反应研究、放射性束流开展的天体物理核反应研究以及其它有关的核反应研究进行了评述，并对其可能的发展作了一些探讨 .The study of total nuclear reaction cross section, nuclear fusion reaction,nuclear reaction of astrophysics and related reactions induced by radioactive nuclear beam are reviewed in this paper. The future development of this field is discussed.     

Cross sections of Au at 10 A GeV and of Pb at 158 A GeV

We have measured total and elemental charge changing cross sections fro the fragmentation of 10 AGeV ¹⁹⁷Au- and 158 AgeV ²⁰⁷Pb-beams interacting with different targets (C, CH₂, Al, Cu, Ag, and Pb) using stacks of CR-39 and of BP-1 nuclear track detectors. Electromagnetic dissociation (ED) significantly contributes to these interactions besides nuclear fragmentation. Based on the factorization of elemental cross sections it is possible to separate electromagnetic dissociation cross sections from the measured data. The analysis of the Au 10 AGeV experiment is completed. For the Pb-beam the analysis is in progress. First results will be reported.     

Analysis of Neutron Double-Differential Cross Section of n＋^14N at 14.2 MeV

Abstract By using a new reaction model for light nuclei, the double-differential cross section of n ^14N reactions at En=14.2 MeV has been analyzed. In the case of n ^14N reactions, the reaction mechanism is very complex, there are over one hundred opened partial reaction channels even at incident energy En=14.2 MeV. In this paper the opened reaction channels are listed in detail. With LUNF code the model calculation is performed to analyze the doubledifferential cross sections of total outgoing neutron. The calculated results agree fairly with the experimental data. The results indicate that the pre-equilibrium mechanism dominates the whole reaction processes, and the recoil egect in light nuclear reactions is essentially important. 5He emission has been considered, but it is only a small contribution to thedouble-differential cross section at incident energy En=14.2 MeV.     

Projectile fragmentation of O and S at 3.65 GeV/n on several targets

We investigate the charge changing collisions for ¹⁶O and ³²S beams at 3.65 GeV/n on several targets, by using Solid State Nuclear Track Detectors (SSNTD). Track measurements were performed by an automatic measurement system. We determined the total charge changing cross sections and the elemental cross sections for the production of fragments of charge 9 ≤ Z ≤ 14. Comparison with theoretical models as well as with experimental data are given.     

Projectile fragmentation of silicon ions at 490 A MeV

Fragmentation cross sections are essential input parameters for propagation calculations which describe the effect of shielding against cosmic ray heavy nuclei by the walls of spacecraft or planetary habitat. Cross sections for the breakup of different elements are needed for different types of target material and for a wide range of energy.

For this purpose, we have extended our studies of projectile fragmentation. By using stacks containing CR-39 track detectors and targets ranging from CH₂ to Pb we have measured total and elemental fragmentation cross sections for fragments with charges Z_F>5, for silicon projectiles with energies of 490 AMeV. These new data sets allow us to improve our knowledge about the target and energy dependence of fragmentation cross sections.     

Unconventional Medium Effect in K+-and π+-Nucleus Scattering

The ratios of total cross section of K⁺-nucleus to K⁺-deuterium at 400 MeV/c≤pk≤800 MeV/c for ⁶Li, ¹²C, ²⁸Si, ⁴⁰Ca and the differential cross section of π⁺-¹²C scattering at p_π= 800 MeV/c are calculated by taking into account the unconventional medium effect.An enhancement of both the K⁺-and π⁺-nucleus scattering cross sections is obtained.     

Calculations of particle and heavy ion interactions with space shielding materials using the SHIELD-HIT transport code

Spectra of secondary particles produced by nucleus–nucleus interactions and heavy-ion interactions in the extended targets of interest for space research were calculated using the Monte Carlo code SHIELD-HIT. This code simulates the interactions of hadrons and atomic nuclei of arbitrary charge and mass number (Z,A) with complex extended targets in a wide energy range, from 10 GeV/u down to 1 MeV/u, and to thermal energies in the case of neutrons. Inelastic nuclear reactions in SHIELD-HIT are simulated using the Russian models of nuclear reactions. The total reaction cross sections evaluated by these models are discussed for proton and carbon interactions with different nuclei in a wide energy range. Production of secondary neutrons and charged secondary particles from the thick targets of lead, water and PMMA irradiated by ⁴He, ¹²C and ²⁸Si ions of different energies was calculated and compared with the experimental data. The results obtained by SHIELD-HIT are in reasonable agreement with experiments and are promising for further applications in space research.     

Stopping powers of CR-39 nuclear track material for Z=1−14 ions with 0.25–2.8 MeV/u

Experimental studies of the slowing down of ¹H, ⁴He, ⁷Li, ¹¹B, ¹²C, ¹⁴N, ¹⁶O, ²³Na, ²⁷Al and ²⁸Si ions in CR-39 nuclear track etch material in the ion energy range 0.25–2.8 MeV/u are presented. The ion stopping powers obtained are compared to the predictions of two recent semiempirical models for calculating ion stopping powers. The predictions are found to clearly underestimate the observed stopping powers for ⁷Li, ¹¹B, ¹²C, ²³Na, ²⁷Al and ²⁸Si ions.     

Measurements of the 107Ag neutron capture cross sections with pulse height weighting technique at the CSNS Back-n facility

Silver indium cadmium (Ag-In-Cd) control rod is widely used in pressurized water reactor nuclear power plants, and it is continuously consumed in a high neutron flux environment. The mass ratio of ¹⁰⁷Ag in the Ag-In-Cd control rod is 41.44%. To accurately calculate the consumption value of the control rod, a reliable neutron reaction cross section of the ¹⁰⁷Ag is required. Meanwhile, ¹⁰⁷Ag is also an important weak r nucleus. Thus, the cross sections for neutron induced interactions with ¹⁰⁷Ag are very important both in nuclear energy and nuclear astrophysics. The (n,γ) cross section of ¹⁰⁷Ag has been measured in the energy range of 1-60 eV using a back streaming white neutron beam line at China spallation neutron source. The resonance parameters are extracted by an R-matrix code. All the cross section of ¹⁰⁷Ag and resonance parameters are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00010.     

Ω＋Ω→（ΩΩ）Jπ=0＋＋X Cross section Calculation

The cross sections of Ω+Ω→(ΩΩ)_J^π=0⁺+X are studied by using an effective Hamiltonian method. The results are σ_{Ω+Ω→(ΩΩ)0⁺+γ}=0.03～0.16×10^-29 cm² for p_Ω=100～400 MeV, and the cross sections of η production are about 10^-28 cm² for p_Ω > 880 MeV.