Thick skin in neutron/proton-rich sodium isotopes

Nucleon (both neutron and proton) density distributions of the chain of sodium isotopes are calculated using a semi-phenomenological model of nuclear density which incorporates correctly the asymptotic behaviour and the behaviour near the centre. The experimental charge root-mean-square radii and the single neutron and proton separation energies, required as input, are used. The calculated interaction cross-sections using these densities in the Glauber model agree well with the experiment. The calculated neutron rms radii r _n and the nuclear skin thickness ( r _n - r _p) closely agree with the corresponding experimental values and also are consistent with the Relativistic Hartree-Bogoliubov (RHB) calculations. Received: 24 April 2001 / Accepted: 28 June 2001     

Neutron skin effect of some Mo isotopes in pre-equilibrium reactions

The neutron skin effect has been investigated for even isotopes of molybdenum at 25.6 MeV ^{94 − 100}Mo(p, xn) reaction using the geometry-dependent hybrid model of pre-equilibrium nuclear reactions. Here the initial neutron/proton exciton numbers were calculated from the neutron/ proton densities obtained from an effective nucleon–nucleon interaction of the Skyrme type. Initial exciton numbers from different radii of even Mo isotopes were used to obtain the corresponding neutron emission spectra. In this investigation the calculated results are compared with the experimental data as also with each other. The results using central densities in the geometry-dependent hybrid model are in better agreement with the experimental data.     

14.77 MeV neutron-induced nuclear reaction cross sections for zinc,yttrium, and molybdenum targets

The cross sections for neutron-induced nuclear reactions on natural zinc, yttrium, and molybdenum targets were measured at a neutron energy of 14.77 ± 0.17 MeV using the activation technique, offline gamma-ray spectrometry, and a detailed covariance analysis. The uncertainty in the statistical model calculations of cross sections for the (n, 2n), (n, p), (n, α), and (n, γ) reactions with natural zinc, yttrium, and molybdenum at neutron energies from 13 to 17 MeV was calculated using the TALYS-1.96 nuclear code. The measured cross sections of the present study were compared with the experimental cross sections reported in the EXFOR database, the cross sections were calculated with the TALYS-1.96 and EMPIRE-3.2.3 nuclear codes and the evaluated nuclear data from the TENDL-2019, JENDL-5, and ENDF/B-VIII.0 libraries.     

A realistic model of superfluidity in the neutron star inner crust

A semi-microscopic self-consistent quantum approach developed recently to describe the inner-crust structure of neutron stars within the Wigner-Seitz (WS) method with the explicit inclusion of neutron and proton pairing correlations is further developed. In this approach, the generalized energy functional is used which contains the anomalous term describing the pairing. It is constructed by matching the realistic phenomenological functional by Fayans et al. for describing the nuclear-type cluster in the center of the WS cell with the one calculated microscopically for neutron matter. Previously, the anomalous part of the latter was calculated within the BCS approximation. In this work corrections to the BCS theory which are known from the many-body theory of pairing in neutron matter are included into the energy functional in an approximate way. These modifications have a sizable influence on the equilibrium configuration of the inner crust, i.e. on the proton charge Z and the radius R _c of the WS cell. The effects are quite significant in the region where the neutron pairing gap is larger.     

相对论平均场理论对Se，Kr，Sr和Zr同位素链形状共存的系统研究

在约束形变的相对论平均场理论下,用NL3参数组系统地研究了Se,Kr,Sr和Zr四个同位素链中的偶-偶核,理论计算的基态束缚能和实验值符合得非常好.通过对这些核的位能曲面的分析,发现在此区域内有着丰富的形状共存现象,系统地指出可能存在形状共存现象的原子核,并且进一步指出在这些核的位能曲面上两个能量极小点的能量差.另外通过对位能曲面以及单中子能级的研究,提出在此区域内N＝70可能是一个中子幻数. 关键词： 形状共存 相对论平均场 位能曲面 幻数     

厚闪烁体内次级中子对快中子图像质量的影响研究

利用编制的快中子照相数值模拟程序(FNRSC)模拟计算了入射中子能量为14 MeV时,厚度5—300 mm闪烁体内次级中子对快中子图像质量的影响,结果表明闪烁体厚度d<50mm时,次级中子对图像的影响强烈依赖于闪烁体厚度,而当d>50 mm时,次级中子对图像的影响趋于饱和.将文献中利用蒙特卡罗中子-光子输运程序(MCNP)计算的次级中子对图像影响和文中计算结果进行了对比,给出了二者存在差异的主要原因：次级中子分布对入射中子空间分布的强烈依赖性;能量沉积和荧光输出这两种计算方法对 关键词： 14 MeV中子 快中子照相 次级中子 Monte Carlo模拟     

Structure factors for neutron scattering on tunnelling methyl groups in nitromethane

The elastic, quasielastic and inelastic structure factors for neutron scattering on CH₃ groups tunnelling in a sinusoidal hindering potential with threefold symmetry are calculated as a function of the momentum transferQ. A comparison is made with data on methyl groups in nitromethane obtained with high resolution inelastic neutron scattering experiments at high momentum transfer.     

Neutron Matter Properties Using Skyrme Interaction

The purpose of the present work is to extend earlier nuclear matter calculations to study the properties of neutron matter. The binding energy per particle, symmetry energy, single particle potential, effective mass, and magnetic susceptibility are calculated using a modified Skyrme interaction. These are calculated as a function of the Fermi momentum k_f in the range 0 < k_f < 2 fm^?1. Two sets of the interaction parameters are obtained by fitting the interaction parameters using the available information on neutron matter. Relativistic corrections to the order 1/c² are also calculated. The relativistic corrections are very small and they increase as k_f is increased.     

Neutron-, ion-, and electron-energy spectra in a 1 kJ plasma focus

The neutron energy spectrum (4 Torr deuterium) was determined from 30 m flight histograms.—An average energy of approximately 100±20 keV of the neutron producing deuterons within an assumed cone angle of approximately 40 degrees along thez-axis was calculated by means of the target beam model.—Shadow bar techniques reveal that only 10% of the neutrons are produced in the ≈1 cm long focus.—Experimental time of flight analysis confirms that the ion spectrum extends from less than 70 to greater than 400 keV. The electron spectrum in 8 Torr hydrogen follows a ≈3 keV Boltzmann distribution, but demonstrates the presence of nonthermal >100 keV electrons.     

Magnetic neutron-electron scattering; use of thef-sum rule to assess the effect of electron correlations,lattice interaction and magnetic field

We have calculated thef-sum rule for magnetic neutron scattering off electrons. Correlations alter the cross-section significantly at intermediate scattering vectors. Field induced effects are most significant at small scattering vectors, and the sum rule diverges in the limit of zero scattering vector. This feature is attributed to the field induced coupling of neutrons to the lowest energy Landau level and the collective density oscillation (hybrid mode). Our interpretation is based on an RPA calculation of the response function for neutron scattering from a magnetized plasma. The contribution to the cross-section from the electron-phonon interaction is also assessed, and it is found to increase with decreasing scattering vector.     

Equation of State of Hot Neutrino Opaque Interior Matter of Neutron Star

The equation of state of hot neutrino opaque interior matter of the neutron star and some of its properties such as the free energy, effective mass, adiabatic index, and temperature are calculated along both isothermal and isentropic paths with the AV ₁₈ and AV ₁₄ potentials using the lowest order constrained variational method. We have shown that the calculated equation of state with the AV ₁₈ potential is harder than with the AV ₁₄ potential. It is found that there is no phase transition in the hot neutrino opaque interior matter of the neutron star. We have shown that for all values of density and entropy, the adiabatic index of neutron star matter is greater than . It is shown that our calculated equations of state obey the causality condition.     

Measurements of the partial cross section for the reaction 48Ti(n, γ1)49Ti and estimation of the radiative strength functions for E1 and M1 transitions

The partial cross section for radiative neutron capture by ⁴⁸Ti nuclei was measured as a function of neutron energy. The method of neutron spectrometry used is based on the shift in the energy of the primary γ transition in response to a change in the energy of the captured neutron. The reaction ⁷Li(p, n)⁷Be was used as a neutron source. Protons were accelerated by a Van de Graaff electrostatic generator up to energies of 60 keV above the reaction threshold, which provided neutron energies in the range from 10 to 120 keV. The partial widths of some resonances were determined. The radiative strength functions of E1 and M1 transitions to the first excited state were calculated. __________ Translated from Yadernaya Fizika, Vol. 66, No. 1, 2003, pp. 47–50. Original Russian Text Copyright ? 2003 by Voinov, Serov, Popov, Gundorin, Kobzev, Parzhitski.     

Model of forming deuteron fluxes and neutron generation in an axial plasma diode with inertial ion confinement

A model of forming deuteron fluxes and neutron generation in an axial plasma diode with two external anodes and a transparent internal hollow cathode is suggested. Such configuration provides longitudinal deuteron oscillations (inertial confinement) and required frequency of collisions with slow deuterons in the cathode plasma. On the basis of the suggested model of neutron generation, the neutron flux generated in the course of D(d, n)³ He nuclear reactions is approximately calculated. The examined diode system seems to be promising for the development of compact controllable neutron sources with increased operation lifetime and transverse size no more than 5 cm.     

Neutron Drip Line for Nuclei in the Vicinity of the Neutron Magic Number N = 184

Ground-state properties of even-even nuclei were calculated over a broad region of mass numbers, including nuclei that contain a neutron excess in the vicinity of the neutron drip line. The calculation of the properties of such nuclei relied on the method of the relativistic and the nonrelativistic mean field and took into account the axial deformation of nuclei. Particular attention was given to nuclei beyond the theoretical neutron drip line, which form a peninsula of nuclei in the (N, Z) space at N = 184 that are stable against the emission of one or two neutrons.

     

An investigation into the accuracy of the albedo dosimeter DVGN-01 in measuring personnel irradiation doses in the fields of neutron radiation at nuclear power installations of the joint institute for nuclear research

The calculated results of research into the accuracy of an individual albedo dosimeter DVGN-01 as it corresponds to the personal equivalent dose for neutrons H _p (10) and to the effective dose for neutrons E _eff in the neutron fields at Joint Institute for Nuclear Research Nuclear Power Installations (JNPI) upon different geometries of irradiations are presented. It has been shown that correction coefficients are required for the specific estimation of doses by the dosimeter. These coefficients were calculated using the energy sensitivity curve of the dosimeter and the known neutron spectra at JNPI. By using the correction factors, the uncertainties of both doses will not exceed the limits given to the personnel according to the standards.     

The effect of the initial exciton numbers on <Superscript>54,56</Superscript>Fe(<Emphasis Type="Italic">p,xp</Emphasis>) Pre-Equilibrium Reactions

In pre-equilibrium nuclear reactions, the geometry-dependent hybrid model is applied with the use of the neutron and proton densities to investigate the effect of initial exciton numbers on the nucleon emission spectra. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained within the Skryme-Hartree-Fock method with SKM* and SLy4 forces on target nuclei in the ^54,56Fe(p, xp) reaction at 61.5-MeV incident proton energy by using a new calculationmethod of Tel et al. Also, the differences between the initial exciton numbers for protons and neutrons as a function of nuclear radius, focusing on systematic discrepancies correlated to differences in the proton and neutron densities have been investigated.     

Optimizing the collimator/shielding configuration of the NG-430 neutron generator

Computer optimization of the collimator and shielding of the NG-430 neutron generator at the Institute for Nuclear Research, Russian Academy of Sciences, is performed. The purpose of the optimization is to reach an acceptable value of the ratio Q between the neutron fluence in the investigated target (the signal) and the neutron fluence in the area of the detecting equipment (the background). The fluences of fast neutrons in the target and detectors are calculated by the Monte Carlo method. The influence of the walls of the experimental hall is taken into account. The optimal configuration of the assembly that provides the required Q value is found.     

Pre-equilibrium emission effect in (n,p) reaction cross-sections at 14.8 MeV

The influence of pre-equilibrium emission on (n, p) reaction cross-sections at 14.8 MeV has been studied. Cross-sections for (n, p) reactions have been measured by the activation technique at 14.8 .1; 0.5 MeV neutron energy. The experimental cross-section values have been compared with the calculated values at 14.8 MeV with and without considering the pre-equilibrium emission. Equilibrium calculations have been performed according to the statistical model of Hauser and Feshbach while the hybrid model has been used to include the pre-equilibrium contribution. Pre-equilibrium emission has been considered only in the first emission step. The comparison of experimental and calculated values clearly indicates the presence of pre-equilibrium emission.     

Systematic study of survival probability of excited superheavy nuclei

The stability of excited superheavy nuclei (SHN) with 100 ⩽ Z ⩽ 134 against neutron emission and fission is investigated by using a statistical model. In particular, a systematic study of the survival probability against fission in the 1n-channel of these SHN is made. The present calculations consistently take the neutron separation energies and shell correction energies from the calculated results of the finite range droplet model which predicts an island of stability of SHN around Z = 115 and N = 179. It turns out that this island of stability persists for excited SHN in the sense that the calculated survival probabilities in the 1n-channel of excited SHN at the optimal excitation energy are maximized around Z = 115 and N = 179. This indicates that the survival probability in the 1n-channel is mainly determined by the nuclear shell effects.

     

Energy spectra of delayed neutrons from separated fission products: (III). The precursors 88Br, 90Br, 138I, 140I, 142(Xe+Cs) and 144Cs

Energy spectra of delayed neutrons from the mass-separated fission products ^{88. 90}Br, ^{138, 14}I, ¹⁴²(Xe+Cs) and ¹⁴⁴Cs have been measured. Average level spacings, neutron envelopes and P_n values were calculated and compared with the experimental data. The neutron envelopes are well reproduced for all precursors except ⁹⁰Br and ¹⁴⁰I. For the latter the neutron window predicted by various mass formulae is too wide and a considerable reduction was found necessary to bring calculated envelopes in agreement with the experimental distributions.