Pre-formation Probability of ^5He Cluster in Pre-equilibrium Mechanism

A new reaction model for light nuclei of lp shell is expanded to ^19F with 2s-ld shell nucleus. The double-differential cross sections of total outgoing neutron for n＋^19F reactions at En = 14.2 MeV are calculated and analyzed, and the calculated results agree fairly well with the experimental measurements.     

Fusion Cross Section of $${\mathrm{T(d,n)}}^{4}{\mathrm{He}}$$ and $${}^{3}{\mathrm{He(d,p)}}^{4}{\mathrm{He}}$$3He(d,p)4He Reactions by Four Parameters Formula

Fusion cross sections of light nuclei are calculated by a complex potential and taking into account of conservation of angular momentum and parity. The nuclear potential is assumed to be as simple as a spherical complex square well with a rigid core. Then the nuclear phase shift is extracted from continuity condition of inverse of the logarithmic derivative of the wave functions as a complex quantity. The quantum tunneling probability and cross section are obtained via real and complex components of nuclear phase shift. The obtained results for the two most important light nuclei reactions, \({\mathrm{T(d,n)}}^{4}{\mathrm{He}}\), \({}^{3}{\mathrm{He(d,p)}}^{4}{\mathrm{He}}\) are compared with other theoretical formulas and experimental data. Despite that the theory is simplified as much as possible and the complexities and details of nuclear interactions has been ignored, excellent agreements with experimental data are achieved.     

Neutron Transport Calculations by Using Double-Differential Cross Sections

Some test calculations were carried out to demonstrate the usefulness of double-differential cross sections for neutron transport calculations including anisotropic scattering. A transport code system NITRAN was applied for the purpose. In NITRAN, the anisotropy of elastic and inelastic scattering can be treated in a general form by double-differential total neutron-emission cross sections, which are generated from single-differential and/or original double-differential cross section data base.

The test calculations were performed for neutron flux spectra in aluminum and lead slabs, and also for tritium production rates in a natural lithium sphere. Since the treatment free from collision kinematics is possible by using the double-differential cross sections in the Sⁿcalculations, the discretization of secondary neutron energy distribution becomes independent of the segmentation of angular distribution. A significant improvement due to this independence can be seen in calculating the anisotropy of general inelastic scattering and the extreme anisotropy of elastic scattering by heavy nuclei. For precise anisotropic transport calculations, it is therefore concluded that the nuclear data of double-differential type are more suitable than those of single-differential type.     

Measurement of the double-differential cross section for electronic emission accompanying the interaction of fission fragments with nitrogen and carbon dioxide molecules

Conclusions Experimental data on the double-differential (with respect to angle of emergence and energy of the electrons) cross section for electron emission from nitrogen and carbon dioxide molecules bombarded with fission fragments were obtained under conditions of low data acquisition rate and high background level due to accompanying particles. Russian Science Center of the Russian Federation — A. I. Leipunskii Physics and Power Engineering Institute. Translated from Atomnaya énergiya, Vol. 82, No. 5, pp. 365–369, May, 1997.     

Depth resolution and recoil cross section for analyzing hydrogen in solids using elastic recoil detection with 4He beam

Two aspects of the elastic recoil detection technique for analyzing H and D are described; i) experimental factors which effectively limit the depth resolution in Al film, and ii) determination of the recoil cross section for H(⁴He, ⁴He)H and D(⁴He, ⁴He)D reactions in the range of 1.5–3.0 MeV energy of ⁴He. Both experimental and theoretical estimates of the depth resolution are presented and are in good agreement each other. The theoretical estimate therefore provides a reliable guide to find optimum resolution conditions. The recoil cross section for H is more than double the theoretical Rutherford scattering value and that for D becomes greater than 30 times Rutherford near the resonance energy of 2.1 MeV ⁴He.     

电子阻止截面对平均投影射程计算结果的影响

以氦离子轰击碳靶和镍靶为例，通过五种半经验理论计算与实验结果的比较，指出基于ＢＫ模型的通用计算公式可以在很宽能区范围内得到与实验值非常接近的电子阻止截面。还用Ｂｉｅｒｓａｃｋ给出的一阶线性常微分方程的平均投影射程算法，研究了不同电子阻止截面对平均投影射程计算结果的影响。     

Cross section for the single-electron capture by fast He ions in inert gases

The cross section of the single-electron capture for collisions between dressed ions and He, Ne, and Kr atoms is calculated using the first Born approximation. The electron capture from all shells of target atom and into each excited state of helium atom up to 5^1,3D are take into account. The results of calculations compare with the other experimental and theoretical data.     

The elastic He+d cross section of relevance for knock-on effects in radio frequency heated (He)D plasmas

The cross section for d+³He elastic scattering has been determined for the angular range 20-180° (CM) for beam energies E_d = 0.05 to 11 MeV through combined use of experimental data, Coulomb scattering and extrapolations. The results are used to study, for instance, how the cross section is affected by nuclear interaction contributions. Implications of these results on the calculation of knock on effects in (³He)D plasmas subjected to RF heating and their manifestations in the spectrum of the d + d fusion neutron emission are discussed.     

The calculation of the differential cross sections for recoil protons in 4He-p Scattering

The equation relating phase shift to energy given by the effective range theory for charged particle reactions and the effective range parameters which can well fit the experimental data of P-⁴He elastic scattering have been used to obtain the phase shifts and differential cross sections of protons in p-⁴He elastic scattering. Thereafter the differential cross section of recoil protons in ⁴He-p elastic scattering are calculated through the principle of detailed balance and compared with the experimental data and Rutherford cross sections. Better consistency between experimental and theoretical values than in previous work is achieved.     

Single electron capture in slow He2+-Li collisions

Optical measurements of single electron capture in He²⁺ -Li collisions are reported in the energy range 0.55–10keV/amu. These low energies were inaccessible in our earlier work on the same system [1].Cross sections for emission of the 1s?np (n = 2, 3, 4) Lyman series of He II have been measured with a VUV grazing incidence spectrometer. From these we have deduced the total capture cross section σ_t, and the subshell-selective capture cross sections σ_3p and σ_4p.Correction factors connected with the polarisation of the emitted radiation were applied to our data, using theoretical results of Fritsch and Lin [2], who calculated capture cross sections for nlm?states.Our results for σ_t, are in excellent agreement with very recent charge state selection measurements by Varghese et al. [3]. Both the total and the partial cross sections agree very well with theoretical results by Fritsch and Lin [2]. Comparison with other experimental and theoretical results is also made.     

UV spectroscopy of charge exchange collisions between N5+ ions and H2, He

We report results concerning a spectroscopic study of radiative transitions observed during the collision between N⁵⁺ ions with H₂ and He. Excitation cross section and their energy variation are measured. In addition to the simple electron capture, strong double electron capture is shown with the He target.     

Photonuclear Angular Distribution Systematics in the Quasideuteron Regime

We describe an applications-oriented method for determining continuum photonuclear angular distributions for emission of light particles (n, p, d, t, ³He, and α) in the quasideuteron regime (40≤E _inc≤140 MeV). Based on theoretical considerations by Chadwick and Oblozinsky for the angular forward-peaking in preequilibrium reactions, Kalbach's 1988 angular distribution systematics for a neutron projectile can be straightforwardly modified for use in photon-induced reactions. This results in photonuclear angular distributions which are less forward-peaked than their nucleon-induced counterparts, due to the small momentum carried by a photon. Our pre- dictions are compared against double-differential monochromatic ¹²C(γ, xp) data at 60 and 80 MeV and are seen to describe the measurements fairly well.     

Theoretical calculations and evaluations of n+23Na reaction

The data for neutron-induced reactions are indispensable in a lot of applications of nuclear science and technologies. All reaction cross sections, angular distributions, energy spectra, and double-differential cross sections of neutron, proton, deuteron, triton, and alpha-particle emissions are consistently calculated and analyzed for n+~(23)Na reactions at incident neutron energies below200 Me V, based on nuclear theoretical models. The calculated results are compared with the experimental data and the evaluated data in the ENDF/B-VII, JENDL-4.0,and JEFF-3.2 libraries. In most cases, the calculated results describe the corresponding experimental data well. At the resonance energy region, evaluated experimental data are adopted to fit to the resonance structures.     

用于剂量计算的核反应总截面经验公式

在核物理及核物理应用研究中，利用核反应总截面经验公式进行理论计算具有现实意义。这方面的计算公式很多，本文以中能区应用的Kox经验公式为基础，结合重离子治疗肿瘤计算剂量深度模型的需要，对Kox经验公式的参数进行了修正，使其具有更广泛的应用价值，同时对修正参数的物理意义进行了探讨。     

Emission Probabilities of Gamma Rays from the Decay of 233Pa and 238Np,and the Thermal Neutron Capture Cross Section of 237Np

In order to determine the thermal neutron capture cross section of ²³⁷Np, the relevant γ emission probabilities of the 312-keV γ-ray from the decay of ²³³Pa and the 984-keV γ-ray from the decay of ²³⁸Np are deduced from the ratio of the emission rate to the activity. The emission rate and activity are measured with a Ge detector and a Si detector, respectively. The measured emission probability for 312-keV γ-ray is 41.6±0.9% and that for 984-keV γ-ray is 25.2±0.5%. The emission probabilities are used to correct the thermal neutron capture cross section of ²³⁷Np reported previously, and gives 168±6b. The neutron capture cross section is also determined as 169±6b by α-ray spectroscopic method. The measured emission probabilities and capture cross section are compared with others from references. By averaging these values deduced by different methods, the value of 169±4b is recommended as the thermal neutron capture cross section of ²³⁷Np for 2,200 m/s neutrons.     

One electron capture into excited states and target atom excitation in He+ collisions with Ar

One-electron capture and direct excitation in collisions between He⁺ and Ar in the ion energy range 70–150keV is discussed. The emission cross section of the triplet He I states for the He⁺-Ar collision system is much larger than that for the He⁺-Ne collision system at low ion energies. A qualitative explanation for this difference is given.     

Measurement of Double-Differential Neutron Emission Spectra from Uranium-238

We have performed the measurement of neutron emission spectra from ²³⁸U using a time-of-flight technique, and deduced the following data; (1) the prompt fission neutron spectra for 2 MeV incident neutrons at two emission angles of 90° and 135°, (2) the double-differential neutron emission cross sections at the incident energies of 1.2, 2.0, 4.2, 6.1 and 14.1 MeV. The emission spectra and the cross sections for scattering process were also deduced by subtracting the fission neutrons from the experimental spectra. The experimental results were compared with other experiments and the evaluations of JENDL-3 and ENDF/B-IV.

From the fission spectrum data ranging from 2 to 12 MeV, we have derived the best fit parameters for the Maxwellian and Watt type distribution functions. The experimental spectra are described with the Maxwellian spectrum with temperature of 1.24–1.26 MeV and are softer than both evaluations.

The spectra and cross sections for inelastic-scattering showed substantial disagreement with the evaluations concerning the discrete levels between 0.5 and 1.2 MeV, and continuum neutrons due to evaporation and pre-equilibrium processes. The secondary neutron angular distributions at 14 MeV incident energy were reproduced fairly well with the systematics.     

Measurement of Charged-Particle Emission Double-Differential Cross Section of Fluorine for 14.2MeV Neutrons

We carried out detailed measurement of the double-differential cross sections of fluorine for the emissions of protons, deuterons, tritons, and α-particles with 14.2MeV incident neutrons. An improved charged-particle spectrometer with a pencil DT-neutron beam furnished at the FNS facility of the Japan Atomic Energy Agency enabled us to obtain precise data with a fine energy resolution over a wide energy range and an angular range from 15 to 150°. The present experiment is the first simultaneous measurement of the four different kinds of charged particles and provides useful data to establish a nuclear reaction model of fluorine as well as to confirm previous experimental data. Angular-differential cross sections for several discrete peaks corresponding to excited states of residual nuclei were extracted to discuss the reaction mechanism of charged-particle emission. The obtained data suggest that the charged-particle emission reaction of fluorine has a complicated mechanism in which there are contributions from the direct reaction, pre-equilibrium, and equilibrium processes. The obtained data were compared with the nuclear data evaluated in JENDL-3.3 and ENDF/B-VII.0. The results show large differences in the energy and angular distributions of emitted particles and the charged-particle production cross sections between the measured and evaluated data.