Study of Deuteron Separation Energy Based on Bayesian Neural Network Approach

Deuteron separation energy is not only the basis for validating the nuclear mass models and nucleon-nucleon interaction potential,but also can determine the stability of a nuclide to certain extent.Bayesian neural network(BNN)approach,which has strong predictive power and can naturally give theoretical errors of predicted values,had been successfully applied to study the different kinds of separations except the deuteron separation.In this paper,several typical nuclear mass models,such as macroscopic model BW2,macroscopic-microscopic model WS4,and microscopic model HFB-31,are chosen to study the deuteron separation energy combining BNN approach.The root-mean-square deviations of these models are partly reduced.In addition,the inclusion of physical parameters related to the pair and shell effects in the input layer can further improve the theoretical accuracy for the deuteron separation energy.The results show that the theoretical predictions are more reliable as more physical features of BNN approach are included.

基于全永磁微波离子源钛自成靶的D-D中子源设计研究

介绍了一种基于全永磁微波离子源钛自成靶技术的紧凑型氘氘(D-D)中子源,其设计中子产额为1×10^(9)s^(-1)。该D-D中子源已经进行了800 h以上的测试,系统可重复稳定运行。早期测试结果显示,系统打火频率高、中子产额低,长时间放电后反向电子会烧蚀Al2O3陶瓷窗,导致微波耦合困难,氘等离子体无法点亮。通过在等离子体腔室中添加氮化硼(BN)保护片以及在钛靶与高压电极之间增加电子抑制电阻,有效抑制了Al2O3陶瓷窗的损伤。通过对等离子体电极孔径的优化和降低腔室压力,降低了打火频率,提高了中子的产额。系统优化后,氘离子能量为70 keV、束流强度为5 mA时,中子产额达到了2.0×10^(8)s^(-1)。在氘离子能量为97 keV、束流强度为6.6 mA时,系统中子产额达到5.2×10^(8)s^(-1)。

Electromagnetic nature of the nuclear forces and toroid structure of the deuteron and triton

In this paper we model in a new way the nuclei of deuterium and tritium. We consider the nucleons as toroids that rotate at a constant angular velocity around a line perpendicular to their rotation plane and passing through the center of mass of the nuclei. Based on exact analytical formulas obtained by us for the electrostatic interaction between two spheres with arbitrary radii and charges, we obtain that the known binding energy of the deuteron and triton has an electromagnetic nature. We also obtain through these formulas the force of interaction inside these nuclei. Besides that, within the framework of the classical model we use, we calculate the volumes and mass densities of the nucleons. Throughout all that we use the experimentally obtained results for the radii and masses of the nucleons and nuclei under study. Through our toroid model we confirm the main experimental results obtained for the deuteron and triton not only for the binding energy but also for the magnetic moments, spins and stability.

MEASUREMENT OF NEUTRON SPECTRA FROM THICK Be TARGET BOMBARDED WITH DEUTERONS

Neutron spectra of Be(d,n) reaction were measured for deuteron energies from 13.5 to 22 MeV by using a stilbene scintillator detector and flight time technique.A special calibration method of neutron detector efficiency for higher energy portion was adopted. The spectral neutron yield per unit beam charge on the Be target at 0° was determined. The fluence-averaged mean neutron energies of the neutron spectra are given as a function of the incident energy for several thresholds. The measured neutron spectra have an almost same shape at different incident deuteron energies. High energy portion (En】1.8MeV) and low energy portion (En【2.0MeV)of the neutron spectra were separately measured and they were concerned with each other by normalization. The energy range of whole neutron spectra is 0.7 MeV to 30MeV.

Production of high-energy neutron beam from deuteron breakup

The deuteron breakup on heavy targets has been investigated in the framework of an improved quantum molecular dynamics model,focusing on the production of neutrons near zero degrees.The experimental differential cross sections of neutron production in the 102 MeV d+C reactions were reproduced by simulations.Based on the consistency between the model prediction and experiment,the feasibility of producing a neutron beam through the breakup of deuteron on a carbon target was demonstrated.Because of the nucleon Fermi motion inside the deuteron,the energy spectrum of the inclusive neutron near 0°in the laboratory exhibits considerable energy broadening in the main peak,whereas the long tail on the low-energy side is suppressed.By coincidentally measuring the accompanying deuteron breakup proton,the energy of the neutron can be tagged with an intrinsic uncertainty of approximately 5%(1σ).The tagging efficiency of the accompanying proton on the forward-emitted neutron can reach 90%,which ensures that the differential cross section in the(d,np)channel remains two orders higher than that in(p,n)after considering the measurement of accompanying protons.This enables the application of a well-defined energy neutron beam in an event-by-event scheme.

Study on deuteron formation mechanism in nucleon-induced reactions

The mechanism of deuteron formation in neutron-induced reactions is studied within the framework of the isospin-dependent quantum molecular dynamics model,using the GEMINI code.The influence of the n+p→d reaction channel is investigated by analyzing the deuteron production cross sections in the neutron-induced reactions12C(n,d),16O(n,d),and 28Si(n,d),with incident energies of 20-100 MeV.By including the n+p→d reaction channel when modeling the collision,the deuteron production cross sections increase,optimizing the cross-section results and bringing them closer to the experimental data values.This indicates that the n+p→d reaction channel is an important mechanism for enhancing deuteron production.

Control of Deuteron Ions to Escape from the Magnetic Mirror Bottle by a Perpendicular Supplemental Mirror

We have inquired into a means to decrease the number of charged particles escaping from a loss cone of a magnetic mirror reactor as many as possible. We previously reported the way of installing a supplemental magnetic mirror (which has a cyclotron heating space within) at the exit of a main magnetic bottle. The cyclotron heating space was set to increase a reflection-efficiency of the supplemental mirror. We could not suppress the loss of the escaping deuteron ions sufficiently even with a very long mirror and a very powerful electric field. Then, in this work we propose a new plan of installing another supplemental mirror besides the previous supplemental mirror. A new mirror is set perpendicularly to the center axis of the main bottle. By the addition of the perpendicular mirror, an efficiency of sending back of escaping deuteron ions is considerably theoretically improved. Also in the previous work, since we did not touch how to supply a high-frequency electric field to the cyclotron heating space, here we consider supplying it by an extraordinary-wave with a cyclotron frequency. It is mentioned that propagation of an extraordinary-wave with an electron cyclotron frequency depends on a magnetic field strength and density of escaping electrons.

Further Improvement of Reflection Efficiency of a Magnetic Mirror and Replenishment against Loss of Escaping Deuteron Ions

We reported previously the idea to improve reflection-ability of a magnetic mirror by installing a cyclotron resonance space in the front part of the mirror. However, since the previous analysis was insufficient from the examination after that, we complement the following two things in this work: 1) A simpler procedure of design to make a supplemental magnetic mirror with the simplest magnetic configuration, compared with the procedure reported previously. 2) A peculiar characteristic arising only in reflection of a nonrelativistic charged particle (a deuteron ion).

Excitation Functions for Reactions Induced by Deuteron in Iron

Excitation functions are measured for the products of 55Co,56Co,57Co,58Co,52Mn and 54Mn nuclides by deuteron induced reactions in natural iron in bombardingenergy range below 20 MeV.The stacked activation foil technique is used to carry outthe measurements.The γ-ray spectra of individual foils are determined using a Ge（Li）detector.

Electromagnetic Schr&oumldinger Equation of the Deuteron ²H (Heavy Hydrogen)

The binding energy of the deuteron is calculated electromagnetically with the Schr&oumldinger equation. In mainstream nuclear physics, the only known Coulomb force is the repulsion between protons, inexistent in the deuteron. It is ignored that a proton attracts a neutron containing electric charges with no net charge and that the magnetic moments of the nucleons interact together significantly. A static equilibrium exists in the deuteron between the electrostatic attraction and the magnetic repulsion. The Heitler equation of the hydrogen atom has been adapted to its nucleus where the centrifugal force is replaced by the magnetic repulsive force, solved graphically, by trial and error, without fit to experiment. As by chance, one obtains, at the lowest horizontal inflection point, with a few percent precision, the experimental value of the deuteron binding energy. This success, never obtained elsewhere, proves the purely static and electromagnetic nature of the nuclear energy.

On Dineutron and Deuteron Binding Energies

The binding energy of the deuteron is estimated from the scalar strong interaction hadron theory SSI. The predicted value is 7.7% lower than the measured value. Existence of a spin 1 dineutron with a binding energy 4/5 that of the deuteron or 1.78 MeV is predicted. This is verified by the dineutron, first observed in 2012, in 16Be decay. No free dineutrons are expected to exist in nature as they can decay into deuterons. These binding energies are limited by short range strong interaction internucleon forces but consist of long range electrostatic energies from quark charges.

A Plan to Reclaim Deuterons Escaping from the Loss Cone of a Magnetic Mirror

Research on magnetic mirror reactors has had two serious problems since the beginning stage. One is the magnetohydrodynamic instability due to the negative curvature of the magnetic field lines around the center region of a mirror bottle. Another is the loss of charged particles escaping from the loss cone of a magnetic mirror. We have continued to inquire into a means to solve the latter problem. We here propose a new way which will be able to make a magnitude of a loss angle of a magnetic mirror for deuterons virtually zero.

Superfluidity of Deuterons in Metal-Deuterium Solid Solutionsand Cold Fusion

It is shown that the formation of a Bose-condensate of delocalized deuterons in solid solutions of metals and deuterium leads to the possibility of a d-d-fusion reaction in which one superfluid deuteron and one deuteron that does not participate in superfluid motion participate.Overcoming the Coulomb barrier is due to the large kinetic energy of macroscopic superfluid motion.It is shown that the intensity of the nuclear reaction depends on the velocity of the superfluid motion and,as a consequence,on the magnitude of the vector B of the external magnetic field.In the London Electrodynamics approximation,a linear dependence of the power released during the nuclear reaction on the magnitude of the vector B of the external magnetic field is obtained.

Thick Target Neutron Production on Aluminum and Copper by 40 MeV Deuterons

The thick target neutron yields （TTNYs） of deuteron-induced reaction on AI and Cu isotopes are analyzed by combining the improved nuclear models and particle transport effects. The modified Glauber model is employed mainly to produce the peak of double differential cross section for the breakup process, and the exciton model and the Hauser-Feshbach theory are used for the statistical processes. The thin-layer accumulation method is used to calculate the TTNYs considering the neutron attenuation effects in the target. The calculated results are compared with the existing experimental data, and the analysis method can predict the TTNY data well at the deuteron energy of 40 MeV.

The Investigation Capability of Plasma Focus Device for 13N Radioisotope Production by Means of Deuteron Experimental Spectrum

Optimal condition for 13N radioisotope production through 12C (d,n) 13N within plasma focus device is investigated. As the deuteron spectrum follows the empirical power law of the form E-m, it is shown that the activity decreases by increasing the value of m. Unlike the fact that the repetition rate increases the activity, it is possible to achieve higher activities by increasing the bombardment time at a fixed repetition rate.

基于散射实验极化靶的2.5T/1.3K的动态核极化(DNP)系统的开发

动态核极化法(Dynamic Nuclear Polarization,DNP)是利用热平衡下的电子在磁场中的高自旋极化率转移到原子核自旋的技术,从而极大的提高原子核自旋极化率.多种动态极化靶材料已广泛的用于自旋物理散射实验.本文介绍一种简单实用,共同开发的日本山形大学DNP系统,包括超导磁场,氦4蒸发恒冷器,微波系统以及NMR核磁共振检测系统,测得中子靶材料氘带丁醇(D-butanol)中氘核的极化率在2.5 T/1.3 K达到+6.5%.

Bethe-Heitler lepton pair production in the deuteron breakup reaction

We study the lepton pair production via the Bethe-Heitler mechanism in the deuteron breakup reaction.The complete seven-fold differential cross section is calculated with final state interactions taken into account.The deuteron bound state is described by a relativistic covariant deuteron-nucleon vertex.The numerical results indicate that the differential cross section is highly dependent on the lepton's azimuthal angle in regions of small polar angles and exhibits sharp peaks in the distribution over the invariant mass of the generated lepton pair or the two nucleons in the final state.We demonstrate that such a nearly singular feature originates from the collinearity between the produced lepton or antilepton and the incident photon,and it is physically regularized by the lepton mass in our calculation.The final state interaction between the knocked-out nucleon and recoil nucleon redistributes the differential cross section over the missing momentum,with a significant enhancement at a large missing momentum and a suppression in the intermediate region.With a further decomposition of the final state interaction contribution,It is found that the on-shell term dominates the near quasi-elastic region,while the off-shell term dominates the other end.Additionally,we examine the contribution from the interference between the proton amplitude and neutron amplitude,which,as expected,is found negligible even if the proton-neutron rescattering is included.The results of this study can serve as inputs for the analysis and background estimation of multiple exclusive measurements at Jefferson Lab and future electron-ion colliders.

Identification of deuterons at BESIII

The identification of deuterons with momenta in the range of 0.52−0.72 GeV/c is studied with specific ionization energy loss information using a data sample collected by the BESIII detector at center-of-mass energies between 4.009 and 4.946 GeV.Clean deuteron samples are selected using time of flight information.For all data samples,the deuteron identification efficiencies are higher than 95%,with a maximum difference of%between data and Monte Carlo simulation.This verifies the effectiveness of the deuteron identification method based on specific ionization energy loss and provides valuable information for future studies on processes involving deuterons in the final state at BESIII.

重氢原子进入钛晶格中引起“过热”现象的量热实验

氘原子进入钛晶格后产生电解“过热”现象。对“过热”热量的准确测量是判定电解过程中是否有“过热”的重要依据。采用我们研究的大功率开放量热设备［２］，用重水进行电解实验。出现了“过热”，“过热”功率为１６－６９瓦，±０３瓦，分别为输入电功率的３０％－３２％。

离子源及厚靶参数对氘氚反应中子源中子产额的影响

用厚靶氘氚(D-T)反应中子产额的计算方法模拟计算了入射氘离子能量为120 keV时D-T中子源的中子产额。研究了氘离子源产生的束流中单原子氘离子(D+)及双原子氘离子(D2+)比例对中子产额的影响。结果表明,提高D+比例,同时降低D2+比例将有效提高中子产额。另外还研究了不同靶膜材料及组分引起的中子产额变化。表明中子产额与靶膜中氚的含量成正比,与靶膜元素的原子质量成反比。同时分析讨论了离子源品质及靶参数对中子源整体性能的影响,得出离子源束流品质的提高对中子源整体的设计至关重要。最后,模拟计算了靶膜表面有氧化层情况下中子产额的变化,并与实验结果作了对比。在此基础上提出了一种新的靶设计方案,并对其物理可行性进行了研究。