Neutron induced reactions in antimony isotopes at 14 MeV

Neutron activation cross-sections in antimony isotopes were measured at an incident neutron energy of 14.2±0.2 MeV. The versatile mixed powder technique and high resolution Ge(Li) detector gamma ray spectroscopy were employed. The measured cross-sections were compared with those reported in literature. The total (n, 2n) cross-sections were compared with the estimates based on statistical theory. The experimental values were found to be smaller than the statistical theory estimates and the resulting diminution was attributed to the precompound effects in (n, 2n) reactions at 14 MeV.     

Gamma-rays from an incomplete fusion reaction induced by 95 MeV 14N

Gamma-rays from the ${}^{159}\text{Tb}\text{(}{}^{14}\text{N}\text{, αx}\text{n}\text{)}{}^{\mathrm{169?x}}\text{Yb}$ reaction, in which non-evaporation α-particles are emitted, have been identified. Yields of E2 cascade transitions suggest that the angular momentum distribution of the entrance channel leading to this reaction is localized just above the critical angular momentum for complete fusion.     

Measurement of the neutron-induced deuteron breakup reaction cross-section between 5 and 25 MeV

High-spin states in ¹⁸⁷Pt have been studied by means of ??-ray spectroscopy techniques. Known bands have been significantly extended and new bands have been found. The band structures are discussed in the framework of the cranking model and negative-parity states are compared with calculations performed with a semi-microscopic axial-rotor plus one-quasiparticle coupling model. Shape coexistence is observed from low excitation energy.     

Neutron activation cross section for Ni isotopes at 14·8 MeV

Neutron activation cross sections for Ni isotopes were measured using Ge(Li)γ-ray spectroscopy of the reaction products. The linear least-squares method was used to resolve the interfering reactions. The results obtained are compared with recent experimental and evaluated data, statistical model and semiempirical calculations.     

Determination of Protein Levels in Nigerian Grains Using 14 MeV Neutron Activation Analysis

Fast (14 MeV) neutrons have been successfully used in investigating the protein content of different food grains (Soya Beans, Sorghum, Maize and Beans) locally grown and consumed in Nigeria. Protein was estimated via nitrogen using the ¹⁴N(n, 2n)¹³N reaction. Quantification of nitrogen was achieved through a γ-γ coincidence counting of 511 keV positron emissions from the decaying ¹³N. The implication of the use of the emitted annihilation positrons, the interference introduced in the analytical energy spectra from other activated target nuclides present in the sample, as well as possible proton “knock on” reactions anticipated from cellulose in grain matrix were assessed, and their contributions to the 511 keV gamma energy resolved. For comparative purposes, replicates of samples analyzed through Fast Neutron Activation Analysis (FNAA) were investigated using the Kjeldahl method. The samples were carried through the Kjeldahl process of pre-digestion (with appropriate catalysts), digestion and titration. The results obtained through the Kjeldahl process were found to be in good agreement with those obtained using FNAA although slightly lower. Protein content (%) of Nigerian grains analyzed varied from a low 8.75 ± 2.96 for sorghum to 35.93 ± 0.31 for soya beans.     

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.     

Isomeric cross-section ratios for (n, 2n) reactions induced by 14.7 MeV neutrons in In and Sb

Isomeric cross section ratios were measured for (n, 2n) reactions induced by 14.7 MeV neutrons in In and Sb isotopes. Experimental results were compared with the theoretical calculations performed with the Huizenga and Wandenbosch method.     

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

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 effect in light nuclear reactions is essentially important. 5He emission has been considered, but it is only a small contribution to the double-differential cross section at incident energy En = 14.2 MeV.     

Scattering chamber facility for double-differential cross-section measurement with 14 MeV DT neutron generator at IPR

Measurement of double-differential cross-sections of 14 MeV neutron-induced charged-particle productions is very important for estimating the nuclear heating and radiation damage of a fusion reactor. Only a few experimental data are available even though the nuclear reaction cross-section data of structural materials are important in fusion nuclear technology. In this context, general purpose scattering chamber facility has been developed for accelerator-based 14 MeV DT neutron generator to measure double-differential nuclear reaction cross-section at Fusion Neutronics Laboratory, IPR. It has been designed for experiments using silicon surface barrier detectors for the online detection of charged particles. It offers flexibility in the arrangement of silicon surface barrier detectors.     

Neutron emission from 14N + 165Ho collisions at 35 MeV/u

Neutron emission from ¹⁴N + ¹⁶⁵Ho collisions has been studied at 25 MeV/u incident energy. Energy and angular distributions of the neutrons were measured in coincidence with projectile-like fragments (Li, Be, B, and C) emitted at angles of 10° and 30°. The spectra of neutrons at angles far from the angle of a coincident fragment have been satisfactorily parameterized in terms of a slowly moving, target-like source of temperature 2–3 MeV and a half-beam-velocity source of temperature about 7 MeV. The latter source accounts for about 20% of the detected neutrons for in-plane measurements. The out-of-plane cross sections are smaller. The relevant parameters of the moving-sources parametrization suggest a simple model which qualitatively explains the data in terms of the development of a hot participant zone and its subsequent mass exchange interactions with spectators in the projectile and target nuclei.     

Neutron induced light-ion production from iron and bismuth at 175 MeV

We have measured light-ion (p, d, t, ³He and α) production in the interaction of 175 MeV neutrons with iron and bismuth with low-energy thresholds and for a wide angular range (from 20° to 160°, in steps of 20°). Measurements have been performed with the Medley setup, semi-permanently installed at the The Svedberg Laboratory, Uppsala (Sweden), where a quasi-monoenergetic neutron beam is available and well characterized. Medley is a conventional spectrometer system and consists of eight telescopes, each of them composed of two silicon surface barrier detectors, to perform particle identification, and a CsI(Tl) scintillator to fully measure the kinetic energy of the produced light-ions. We report preliminary double-differential cross sections for production of protons, deuterons and tritons in comparison with model calculations using TALYS-1.0 code. These show better agreement for the production of protons, while the theoretical calculations seem to overestimate the experimental production of deuterons and tritons.     

Total charge-changing and partial cross-section measurements in the reaction of 110 MeV/u C with paraffin

We have measured the total and partial charge-changing cross-sections (Z=5) after the passage of a 110 MeV/u ¹²C beam through an assembly consisting of CR-39 thin detectors and paraffin targets. These experimental cross-sections were compared to the predictions of known models. It was found that the measured total cross-sections agree with the model calculations to within about 8% or even less, while, depending on a model, discrepancies of up to a factor 1.2 higher and up to a factor 2.7 lower values of cross-sections for the production of fragment with Z=5 were observed.     

Boltzmann-Uehling-Uhlenbech calculation of total reaction cross-section and fragmentation cross-section

, and have been calculated via the BUU model with soft EOS and 0.8 times of . The density distribution without any adjustable parameters which comes from the RMF model has been introduced into the BUU calculation to replace the normally used one-parameter square-type distribution. The calculated results can reproduce the experimental data well for both halo- and stable-nuclei-induced reactions. Here or is calculated as the difference between of halo nucleus and core nucleus, by assuming . It indicates that this assumption works very well at high energy in the BUU calculation. More experimental measurements are necessary to test the validity of this assumption at intermediate energy.Received: 12 June 2003, Revised: 29 September 2003, Published online: 27 April 2004PACS: 24.10.-i Nuclear reaction models and methods - 25.60.Dz Interaction and reaction cross-sections - 25.60.Gc Breakup and momentum distributions - 27.20. + n      

Study of5Li around 20 MeV excitation energy by a radiative capture reaction

The nucleus⁵Li has been investigated within an excitation range of 17.8 – 21.1 MeV by measuring γ-rays from the reaction D(τ, γ _o)⁵Li. In this range, excitation functions and angular distributions have been taken. The excitation functions exhibit broad maxima at 20 MeV which indicate, in agreement with other results, a level or a group of levels. Assuming that there is only one resonance, its properties are discussed. On the basis of the existing and the new experimental results, aJ ^π=1/2⁺ assignment is proposed besides the former resultJ ^π=(3/2, 5/2)⁺.     

基于14 MeV中子的烧氚历史诊断模拟研究

针对直接测量16.7 MeV进行烧氚历史诊断所需聚变产额高的情况,模拟研究了利用14 MeV中子与副靶作用产生的非弹伽马进行烧氚历史诊断的情况,计算了几种材料14 MeV中子作用产生的次级伽马能谱以及切伦科夫辐射阈能之上的非弹伽马数目,对副靶材料和厚度进行了选择。计算了14 MeV中子产生的切伦科夫光子时间谱,分析了光电转换器件处伽马、电子以及正电子等噪声信号,分析了气体切伦科夫系统测量统计涨落与聚变中子产额之间的关系,确定了气体切伦科夫系统所适用的最低聚变中子产额,通过测量14 MeV中子与副靶产生的非弹伽马进行烧氚历史诊断较直接测量16.7 MeV伽马可将测量所需聚变中子产额降低2个量级。     

Knockout reaction induced by ~6 He at 61.2 MeV/u

A knockout reaction induced by ⁶He at 61.2 MeV/u was carried out at the HIRFL-RIBLL radioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.     

30MeV/u 40Ar+115In反应中的IMF能谱

测量了30MeV/u ⁴⁰Ar束流轰击¹¹⁵In反应靶时出射的中等质量碎片(IMF)的能谱.通过比较在不同出射角度发射的同一种IMF的能谱,得到了IMF的发射机制随出射角的演化关系.在假定运动源速度和出射离子库仑位垒不随出射角变化的条件下,通过改变发射源的强度和核温度参量完成了对实验测得能谱的运动源拟合,并详细讨论了3个发射源所占份额和源强随出射角的演化关系.