Cross Section Measurements for (n,d*)(n,t) and (n,n'α) Reactions

Cross sections for some (n,d*),(n,t) and (n,n'α)reactions have been measured by using the activation method relative to cross sections of ²⁷Al(n,α)²⁴Na or ⁹³Nb(n,2n)^92mNb reactions in neutron energies around 14MeV.In this paper some of the published cross section data have also been listed and compared with our results.The neutron energies were determined by the method of cross section ratios for the reactions of ⁹⁰Zr(n,2n) ^89m+gZr and ⁹³Nb(n,2n)^92mNb.     

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.     

Measurements of the Cross Sections and A y for D(p, n) Inclusive Breakup Reaction at 170 MeV

The effects of three-nucleon force (3NF) has been actively studied by using the nucleon–deuteron (Nd) scattering states. The differential cross sections of the elastic Nd scattering at the energy below 150 MeV can be well reproduced by incorporating 3NF in the Faddeev calculation based on modern nucleon–nucleon (NN) interactions. On the other hand, the differential cross sections of Nd elastic and inelastic scatterings at 250 MeV show large discrepancies between the data and the Faddeev calculations with 3NF. It indicates the presence of the missing features of the three nucleon system at this energy region. For the systematic study about the energy dependence of this large discrepancies, we measured the differential cross sections and the vector analyzing power A _y for the ²H(p, n) inclusive breakup reaction at 170 MeV. The experiment was carried out at RCNP by detecting scattered neutrons by using the neutron detector NPOL3. The data was compared with the results of the Faddeev calculations with and without the 3NF.     

Cross section measurements for (n, 2n),(n, α)(n,p), and reactions on rhenium isotopes around 14 MeV neutrons and their theoretical calculations of excitation functions

Cross-section data of the ~(185)Re(n,2 n)~(184)mRe,~(185)Re(n,2 n)~(184)Re,~(185)Re(n,α)~(182 m14+m2+g)Ta,~(187)Re(n2 n)~(186 g,(m))Re,~(187)Re(n,α)~(184)Ta,and ~(187)Re(n,p)~(187)W reactions were measured at four neutron energies,namely 13.5,14.1,14.4,and 14.8 MeV,by means of the activation technique,relative to the reference cross-section values of the~(93)Nb(n,2 n)~(92 m)Nb reaction.The neutrons were generated from the T(d,n)~4 He reaction at the K-400 Neutron Generator at China Academy of Engineering Physics.The induced y activities were measured using a high-resolution γ-ray spectrometer equipped with a coaxial high-purity germanium detector.The excitation functions of the six abovementioned nuclear reactions at neutron energies from the threshold to 20 MeV were calculated by adopting the nuclear theoretical model program system Talys-1.9 with the relevant parameters properly adjusted.The measured cross sections were analyzed and compared with previous experiments conducted by other researchers,and with the evaluated data of BROND-3.1,ENDF/B-Ⅷ.0,JEFF-3.3,and the theoretical values based on Talys-1.9.The new measured results agree with those of previous experiments and the theoretical excitation curve at the corresponding energies.The theoretical excitation curves based on Talys-1.9 generally match mo st of experimental data well.     

Further Analysis of Neutron Double-Differential Cross Section of n ＋ ^16O at 14.1 MeV and 18 MeV

By using a new reaction model for light nuclei, the double-differential cross section of total outgoing neutron with LUNF code for n＋^16O reactions at En=14.1 MeV and 18 MeV have been calculated and analyzed. In this paper the opened reaction channels, which have contribution to emitting the neutrons, are listed in detail. To improve the fitting results the direct inelastic scattering mechanism is involved. The calculating results agree fairly well with the experimental data at E,~ = 14.1 MeV and the deviation from calculated results and experimental data in low energy region at En= 18 MeV has been analyzed. Since the possibility of 5He has been affirmed theoretically [J.S. Zhang, Sci. Chin. G 47 （2004） 137], so 5He emission from n＋ ^16O reaction is taken into account, which plays an important role at the region of the outgoing neutron energy εn〈3 MeV in total outgoing neutron energy-angular spectrum. The calculated results indicate that the pre-equilibrium mechanism dominates the whole reaction processes, and the recoil effect in light nuclear reactions is essentially important.     

Proposal for the Simultaneous Measurement of the Neutron–Neutron and Neutron–Proton Quasi-Free Scattering Cross Section via the Neutron–Deuteron Breakup Reaction at E n = 19 MeV

In order to confirm or refute the present discrepancy between data and calculation for the neutron–neutron quasi-free scattering cross section in the neutron–deuteron breakup reaction, we describe a new experimental approach currently being pursued at TUNL.     

Differential Cross Section for Elastic Deuteron–Proton Scattering at the Energy of 700 MeV per Nucleon

The results of measurements of the differential cross section for elastic deuteron–proton scattering at the energy of 700 MeV per nucleon that were performed at the internal target station of the nuclotron at the Joint Institute for Nuclear Research (JINR, Dubna) are presented. These data were obtained at angles in the range between 70? and 120? in the c.m. frame. The angular dependence obtained in this way is compared with world-averaged data at similar energies and with the results of theoretical calculations performed within the relativistic theory of multiple scattering.     

Cross sections for some (n,p) and (n, α) reactions

The cross sections for the Mg²⁴(n, p) Na²⁴, Al²⁷(n, α)Na²⁴, Si²⁸(n, p)Al²⁸, Cr⁵²(n, p)V⁵² and Fe⁵⁶(n, p)Mn⁵⁶ reactions have been measured for neutrons produced by the H³(d, n) He⁴ reaction. The activation method was used, with the gamma rays which are emitted following beta decay being counted with a Na(Tl) scintillation crystal. The Mg²⁴(n, p)Na²⁴ cross section is found to be 219±26 mb at 13.0 MeV. The Al²⁷(n, σ)Na²⁴ cross section varies smoothly from 139 mb at 13.0 MeV to 106 mb at 15.7 MeV. The Si²⁸(n, p)Al²⁸ cross section changes smoothly from 370 mb at 12.3 MeV to 160 mb at 18.3 MeV, with a broad peak at 13.5 MeV with the maximum value of 380 mb. The Cr⁵²(n, p)V⁵² cross section decreases slowly from 125 mb at 12.3 MeV to 72 mb at 18.3 MeV. The Fe⁵⁶(n, p)Mn⁵⁶ cross section is found to be 131±15 mb at 15.3 MeV. The results are generally in agreement in those cases where previous results of others exist.     

Calculations on (γ, p) and (γ, n) reactions at photon energies between 40 and 100 MeV

Shell-model calculations with and without short-range correlations have been carried out for the reactions (γ, p) and (γ, n) in the energy region from 40 to 100 MeV. The cross sections for the ¹⁶O(γ, p)¹⁵N process have been investigated in the single-particle model. The results strongly depend on the initial state wave functions especially at high energies. There are large effects on the cross sections if orthogonality between bound and continuum states is violated. For the reaction ¹⁶O(γ, n)¹⁵O it is shown that short-range correlations in the ground state of ¹⁶O do not contribute appreciably to the cross sections, at least up to a photon energy of 100 MeV.     

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.     

Measurement of the 2H(p,n) Breakup Reaction at 170 MeV and the Three-Nucleon Force Effects

The effects of three nucleon force (3NF) have been actively studied via the nucleon–deuteron (Nd) scattering states. The differential cross sections and the vector analyzing powers A _y of the ²H(p, n) inclusive breakup reaction at 170 MeV were measured for the study of 3NF effects in the intermediate energy region. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD₂) target and the energy of scattered neutrons were measured by using TOF method. The data were compared with the Faddeev calculations based on modern nucleon–nucleon (NN) forces with and without the 3NF. Concerning the differential cross sections, we can see large discrepancies between the data and the calculations in the region of scattered neutron energies are low, which is similar to the results of the ²H(p, p) inclusive breakup reaction at 250 MeV.     

Energy deposition and GDR emission in the reaction 209Bi(α,α′) at 240 MeV

Neutron fold distributions measured for the reaction ²⁰⁹Bi(α,α′) at 240 MeV have been analyzed with the help of Statistical Model calculations to determine the distribution of excitation energy, E_x, in the primary target fragments as a function of the projectile energy loss, EL. The reconstructed distributions in excitation energy feature a plateau which extends from the kinematical limit E_x = EL to very small excitations, indicating a variety of interactions of the beam particles with the target nucleus. The requirement of an additional coincidence with a light charged particle leads to the selection of a significant higher average excitation energy. Those results are extrapolated to explore the effects of including the excitation energy distributions in the analysis of previous GDR measurements in ²⁰⁸Pb. Corrections of the derived GDR parameters due to the partial transfer of excitation energy are suggested.     

Cross sections for proton induced reactions on 41K and for the reaction 62Ni(α, p)65Cu

Excitation functions have been measured for ⁶²Ni(α, p)⁶⁵Cu in the energy range 6.5–9.0 MeV, for ⁴¹K(p, α)³⁸Ar in the range 0.8–2.6 MeV, for ⁴¹K(p, γ)⁴²Ca, ⁴¹K(p, αγ)³⁸Ar, ⁴¹K(p, nγ)⁴¹Ca, and ⁴¹K(p, p'γ)⁴¹ in the range 0.6–4.0 MeV, and for ⁴¹K(p, n)⁴¹Ca from threshold to 3.0 MeV. Cross sections have been extracted from the data and these are compared with statistical-model calculations based on global optical model parameters. Alternative parameter sets have been tried for the ⁶²Ni(α, p)⁶⁵Cu data and published data for ⁶²Ni(α, γ)⁶⁶Zn and ⁶²Ni(α, n)⁶⁵Zn, and both these and the global parameters have been used in statistical-model calculations of ⁶⁵Cu(p, γ)⁶⁶Zn, ⁶⁵Cu(p, n)⁶⁵Zn and ⁶⁵Cu(p, α)⁶²Ni cross sections, which are compared with published data for these reactions. Both the global and the alternative parameters lead to very good agreement with experiment for all six reactions. Alternative parameters have been tried for the ⁴¹K + p reactions also. The global parameters lead to agreement to within a factor of 2 and the alternative parameters lead to agreement to within a factor of 1.3. The ⁴¹K + p alternative parameters are used in calculations of ⁴¹Ca(n, γ)⁴²Ca, ⁴¹Ca(n, p)⁴¹K and ⁴¹Ca(n, α)³⁸Ar cross sections, and these and the experimental ⁴¹K + p data are used in calculations of thermonuclear reaction rates under stellar conditions for the ⁴¹Ca + n and ⁴¹K + p reactions.     

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.     

中重核14.5MeV (n,2n),(n,3n)反应截面的系统学计算

本文从中子核反应机制出发,讨论(n,2n),(n,3n)反应过程,给出约化截面的计算公式.按照系统学方法计算z=58—83的53个中重核的14.5MeV (n,2n),(n,3n)反应截面,计算结果与实验值符合较好.     

Cross section measurements for （n,p） reaction on stannum isotopes at neutron energies from 13.5 to 14.6 MeV

Utilizing the cross sections for ⁹³Nb(n, 2n)^93mNb or ²⁷Al(n, a)²⁴Na reactions as monitors, the cross sections for the reactions ¹¹⁵Sn(n, p)^115mIn, ¹¹⁶Sn(n, p)^116mIn, ¹¹⁷Sn(n, p)¹¹⁷In and ¹¹⁷Sn(n, p)^117mIn have been measured at neutron energy ranging from 13.5 to 14.6 MeV through activation technology. Then, the results of present work were compared with the published experimental data.     

The reactions 10B(n,t)αα, 7Li(n,t)αn and 6Li(n,d)αn at 14.4 MeV

The reactions ¹⁰B(n, t)αα, ⁷Li(n, t)αn and ⁶Li(n, d)αn have been studied at 14.4 MeV. The energy spectra indicate the importance of the sequential decay mechanism in these processes. The Phillips-Griffy-Biedenharn model gives a good fit to the data. No evidence of spatial localization has been observed.