The Cross Section Measurements for the 100Mo(n2n)99Mo,96Mo(n,p)96Nb and 92Mo(n,α)89m+gZr Reactions

The cross sections for ¹⁰⁰Mo(n2n)⁹⁹Mo,⁹⁶Mo(n,p)⁹⁶Nb and ⁹²Mo(n,α)^89m+gZr have been measured by using the activation method relative to the cross sections of ²⁷Al(n,α)²⁴Na in the neutron energy range 13.40—14.79MeV.The comparison between the values of measured and calculated using theory mode was made.The evaluated excition functions for the three reactions are given.     

THE CROSS SECTION MEASUREMENT FOR THE 107Ag(n,2n)106mAg REACTION

The cross section for 107Ag(n,2n)^106mAg has been measured by using the activation method relative to the cross section of ²⁷Al(n,α)²⁴Na in the neutron energy range of 13.50—14.73MeV.The values of 469±22,480±22,503±24,538±25,555±25,572±26mb were obtained at the 13.50,13.60,13.90,14.10,14.35,and 14.73MeV neutron energy,respectively.The results are compared with the published data.The neutron energies were determined by activity ratios of Nb and Zr foils.     

Study of 94Mo through the (n,n′γ) reaction

The ⁹⁴Mo(n, n′γ) reaction has been studied in the neutron energy range 1.5–4.0 MeV. Neutron inelastic scattering cross sections for levels up to an excitation energy of 2.6 MeV have been measured from 1.5 to 3.0 MeV. The results have been analyzed with the optical-statistical and coupled-channels theories. The 1.74 MeV level has been observed and has been assigned to be 0⁺. The branching ratios for the γ-rays deexciting the levels below the 3.5 MeV excitation have also been obtained.     

Evidence for neutron capture through doorway states in29Si

Theγ-ray spectra following neutron capture in silicon have teen recorded in the neutron energy range 2.7–6.2 MeV and partial cross sections forγ-rays to the 2s_1/2 ground state and 1d_3/2 first excited states in²⁹Si determined. The results indicate considerable fluctuations with neutron energy with a prominent resonance peak at 4.6 MeV in the (n,γ _o) cross section. The existence of fluctuations is predicted in a recent theoretical calculation based on a model designed to include single-particle resonances in nuclear reaction processes.     

Measurement of Some (n,2N) Reaction Cross Sections for Producing Long Half-Life Residues

Measurement of (n,2n) reaction cross sections for some nuclides,whose residues have long half-lives,is described.The activation method relative to the ⁹³Nb(n,2n)^92mNb reaction cross section was used.The cross sections of the ¹⁵¹Eu(n,2n)^150mEu、¹⁵³Eu(n,2n)¹⁵²Eu、¹⁵⁹Tb(n,2n)¹⁵⁸Tb and ¹⁰⁹Ag(n,2n)^108mAg reactions in the neutron energy range of 13.50—14.80MeV were measured.The neutron energies in this experiment were determined by means of the method of cross section ratios for ⁹⁰Zr(n,2n)^89m+gZr and ⁹³Nb(n,2n)^92mNb reactions.The results obtained were compared with other existing data.     

THE CROSS-SECTION MEASUREMENTS FOR 59Co(n,p)59Fe,59Co(n,α)56Mn AND 59Co(n,2n)58Co REACTIONS

The cross sections of ⁵⁹Co(n,p)⁵⁹Fe,⁵⁹Co(n,α)⁵⁶Mn AND ⁵⁹Co(n,2n)⁵⁸Co reactions have been measured at neutron energy region of 12.8MeV—17.8MeV by activation method.The coveriance matrix of measured errors was calculated,and the comparison between the values of measured and calculated using theory model was made.The evaluated excitation functions for the three reactions are given.     

The Cross Section Measurement for the Reactions of 48,46Ti(n,p) 48,46Sc 50Ti(n,α) 47Ca and 58Ni (n,2n) 57Ni 58Ni(n,p)58m+gCo

The cross sections for the ⁵⁰Ti(n,α)⁴⁷Ca,⁴⁶Ti(n,p)⁴⁶Sc、⁴⁸Ti(n,p)⁴⁸Sc and ⁵⁸Ni(n,2n)⁵⁷Ni ⁵⁸Ni(n,p)^58m+gCo reactions have been measured by using the activation method relative to the cross sections of the ²⁷Al(n,α)²⁴Na reaction in the neutron energy range of 13.50—14.81MeV.The neutron energies were determined by the cross section ratios of the ⁹⁰Zr(n,2N) ^89m+gZr and ⁹³Nb (n,2n) ^92mNb reactions.The results obtained are compared with the published and to be published data of several authors.     

Intermediate structure of the giant dipole resonance in 54Fe and 56Fe

The cross sections for the (γ, n) reaction on ⁵⁴Fe and ⁵⁶Fe for the high-energy component of the neutron spectrum have been investigated using a neutron spectrometer and a synchrotron with a photon energy range from 5 to 26.3 MeV. Neutron energy spectra have been measured. It is shown that the intermediate structure in the (γ, n) reaction cross section is due to high-energy neutrons and correlates with the structure in the neutron spectrum.     

THE RESPONSE OF A 3×3 BGO DETECTOR ARRAY TO 0.5—21MeV PHOTONS

An array of 9 BGO crystals of 20×20×200mm³ equipped with photomultiplier readout was assembled and tested. Radioactive γ and neutron sources, (p,γ) reactions by low energy protons from Van de Graaff accelerator and (n,γ) reactions by thermal neutrons from nuclear reactor were employed to produce photons in the energy range from 0.5 to 21MeV. The energy response of the array is shown to be linear over the whole range. Data on the energy resolution follow an E^1/2 dependence at low energies, and deviate from it at 4.43MeV and higher energies. Results from the lateral energy deposition of showers were compared with the predictions of the Monte Carlo simulation and found to be in good agreement. Our study demonstrates the feasibility of calibration and monitoring of BGO electromagnetic calorimeter by means of radioactive sources and low energy (p,γ) reactions.     

Theoretical Calculations and Analysis of n+208Pb Reaction for Intermediate Energy Neutron

Based on experimental data of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+Pb reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 1—300 MeV. The cross sections, angular distributions and energy spectra are calculated and analyzed by optical model, distorted wave Born approximation theory, Hauser-Feshbach theory, exciton model and cascade mechanism inside nuclear. The results indicate that the cross sections can be given for n+ ²⁰⁸Pb reactions which are all in good agreement with experimental data.     

CROSS SECTION MEASUREMENT FOR THE REACTION 56Fe（n,p）56Mn

The cross section measurement for the reaction ⁵⁶Fe（n, p）⁵⁶Mn was made using the activation method from 12 MeV to 18 MeV. The absolute cross section was determined at 14.61±0.20 MeV, the value obtained was 108.0±2.7mb. The associated particle method was used to determine the absolute neutron flux and compared with the recoil proton telescope. The agreement between both methods appeared to be within 1—2%. The resulting ⁵⁶Mn activity was measured by using a φ10×7.6cm NaI （Tl） scintillation counter. The counting efficiency of the counter was achieved by means of a standard ⁵⁶Mn source calibrated by the 4πβ-γ coincidence method. The result measured was compared with existing data.     

The Cross-Section Measurements and Evaluations for 58Ni(n,p),60Ni(n,p),62Ni(n,α) and 54Fe(n,p) Reactions

Activation techniques have been used to measure the cross-section for ⁵⁸Ni(n,p),⁶⁰Ni(n,p) and ⁶²Ni(n,α) reactions in the neutron energy range 13.6—17.8MeV.The uncertainty of measured data has been aculated from 3%—7%.The covariance matrixes for measurement error are calculated.Evaluations for ⁵⁸Ni(n,p),⁶⁰Ni(n,p),⁶²Ni(n,α) and ⁵⁴Fe(n,p) crpss-section are made.     

The photodisintegration of 40Ar

High resolution measurements of the (γ, n), (γ, 2n), (γ, p), (γ, np) and (γ, 2p) cross sections of ⁴⁰Ar over a photon energy range of 10 to 28 MeV are reported. From this data, the total photon absorption cross section integrated to 26 MeV is found to be 434 ± 40 MeV mb. The results of a dynamic collective model (DCM) calculation compare favourably with the photoabsorption cross section, supporting the use of the DCM in this mass region. It is confirmed that isospin plays an important role in the decay of the ⁴⁰Ar giant dipole resonance.     

Theoretical Analysis of Double Differential Cross Sections for n+ 238U Reaction

Based on the new measurements of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+U reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 0.1 to 20 MeV. The cross sections, angular distributions, energy spectra and double differential cross sections are calculated and analyzed by optical model, nuclear fission theory, distorted wave Born approximation theory, coupled channel theory, the unified Hauser-Feshbach theory, as well as exciton model. The results indicate that our theoretical model can reasonably analysis n+ ²³⁸U reaction data with neutron energy lower than 20 MeV.     

RESEARCH ON THE 88Y(n,2n) REACTION CROSS SECTION

The cross sections of the neutron induced (n,2n) reaction an the unstable target nucleus ⁸⁸Y in the energy range from 10.3 to 17.4MeV are obtained from the measurement of the ⁸⁷Sr (d,2n) reaction.This work is based on the hypothesis that the formation of the Compound nucleus is independent of its decay.The results are compared with our calculated results and the experimental data and calculated result of Prestwood and his co-worker.The comparison indicates that this work is worthy for further study.     

Calculation and Analysis of Neutron-Induced Reactions on 58Ni Below 150MeV

Based on the experimental data of the total, the nonelastic and the elastic cross sections and the elastic scattering angular distributions for n+⁵⁸Ni reactions, a set of parameters for a neutron optical model potential is obtained in the incident neutron energy region from 0.8—150MeV. Then reaction cross sections, angular distributions, energy spectra, gamma-ray production cross sections and gamma-ray production energy spectra are calculated in terms of the optical model, the distorted wave Born approximation theory, the Hauser-Feshbach theory, the exciton model and the cascade mechanism inside nuclear. The results are analyzed and compared with the existing experimental data and other evaluated data from ENBF/B-6. They are in agreement with each other within error bars.     

Cross Section Measurements of Neutron-Rich Hg Isotopes in Reaction of 28MeV/u 18O with Thick Natural Lead Target

By using 28MeV/u ¹⁸O beam,an on-line melting lead target equipment and 4π-ΔEβ-γcoincident technique,the relative cross section ratios and absolute cross sections of neutron-rich nuclides ^205—208Hg have been measured. The production cross section of ²⁰⁹Hg is extrapolated.The cross section of ²⁰⁷Hg produced by-2p +1n from target decreases suddenly,which may be explained by change of reaction Q value.     

Isomeric ratios in photonuclear reactions of molybdenum isotopes induced by bremsstrahlung in the giant dipole resonance region

We have determined the isomeric ratios of isomeric pairs ^97m,gNb, ^95m,gNb and ^91m,gMo produced in ⁹⁸Mo(γ, p)^97m,gNb, ⁹⁶Mo(γ, p)^95m,gNb and ⁹²Mo(γ, n)^91m,gMo photonuclear reactions in the giant dipole resonance (GDR) region by the activation method. The results were analyzed, discussed and compared with the similar data from literature to examine the role of excitation energy, neutron configuration, channel effect and direct and pre-equilibrium processes in (γ, p) photonuclear reactions. In this work the isomeric ratios for ^97m,gNb from 14 to 19 MeV, for ^195m,gNb from14 to 24 MeV except 20 and 23.5 MeV and for ^91m,gMo at 14 and 15 MeV are the first time measurements.     

MEASUREMENT OF ISOMERIC CROSS-SECTION RATIO IN 133Cs(n,γ) 134Cs REACTION

The isomeric absolute cross-section have been measured for the reaction ¹³³Cs (n,c) ¹³⁴ Cs at 14.8 MeV neutron energy.The results are:σ_n,γ^134mCs=1.76±0.14mb;σ_n,γ^134gCs=5.17±0.41mb;σ_n,γ^134+gCs=6.93±0.55mb.The isomeric cross-section ratio is σ^134m_Cs/σ^134gCs=0.34±0.03 The experimental results are in agreement with the values given by S.M. Qaim andcompared with the theoretical results calculated by Huizenga-Vandenbosch theory.From this, the spin cut-off paramenter σ and the number of γ-Cascades have been de-termined.     

Study of 1/2[660](πi13/2) Rotation Band in 179Au

High-spin states in ¹⁷⁹Au have been studied experimentally using the ¹⁴⁹Sm(³⁵Cl,5n) heavy-ion fusion-evaporation reaction at beam energies of 164—180MeV. Measurements of γ-ray excitation functions, X-γ coincidences and γ-γ-t coincidences were performed with 13 BGO(AC)HPGe and 3 LOAX detectors. Based on these measurements, a rotational band built on the 1/2[660](πi_13/2) Nilsson state has been established for the first time, and this band has been assigned to ¹⁷⁹Au according to the systematic of level structure in odd-A Au nuclei. Properties of the 1/2[660](πi_13/2) band in odd-A Au nuclei are discussed with an emphasis on the band-head energy while changing the neutron number.