Study on the optimal incident proton energy of ^(7)Li(p,n)^(7)Be neutron source for boron neutron capture therapy

Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear reaction.Among various neutron sources,accelerator-based sources have emerged as particularly promising for BNCT applications.The^(7)Li(p,n)^(7)Be reaction is highly regarded as a potential neutron source for BNCT,owing to its low threshold energy for the reaction,significant neutron yield,appropriate average neutron energy,and additional benefits.This study utilized Monte Carlo simulations to model the physical interactions within a lithium target subjected to proton bombardment,including neutron moderation by an MgF_(2)moderator and subsequent BNCT dose analysis using a Snyder head phantom.The study focused on calculating the yields of epithermal neutrons for various incident proton energies,finding an optimal energy at 2.7 MeV.Furthermore,the Snyder head phantom was employed in dose simulations to validate the effectiveness of this specific incident energy when utilizing a^(7)Li(p,n)^(7)Be neutron source for BNCT purposes.

Determination of Proton Drip-line Nucleus of P Isotopes

Researches have been made in recent years in the search of the proton drip-line and halo nuclei of P isotopes both in theory^([1～3])and in experimerit~[4].We have deduced the matter,proton,neutron and halo density distribution of^(25)P with the theory of relativistic-mean-field(RMF)by using the parameter set of

Measurement of the prompt neutron spectrum from thermalneutron-induced fission in U-235 using the recoil proton method

A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.

Probing neutron–proton effective mass splitting using nuclear stopping and isospin mix in heavy-ion collisions in GeV energy region

The ramifications of the effective mass splitting on the nuclear stopping and isospin tracer during heavy-ion collisions within the gigaelectron volt energy region are studied using an isospin-dependent quantum molecular dynamics model.Three isotope probes,i.e.,a proton,deuteron,and triton,are used to calculate the nuclear stopping.Compared to the mn*>mp*case,the mn*<mp*parameter results in a stronger stopping for protons but a weaker stopping for tritons.The calculations of the isospin tracer show that the mn*>mp*parameter results in a higher isospin mix than the mn*<mp*parameter.The rapidity and impact parameter dependences of the isospin tracer are also studied.A constraining of the effective mass splitting using the free nucleons with high rapidity and in a central rather than peripheral collision is suggested.

Yield ratio of neutrons to protons in 12C（d,n）13N and 12C（d,p）13C from 0.6 to 3 MeV

The neutron yield in the12C(d,n)13N reaction and the proton yield in the12C(d,p)13C reaction have been measured using deuteron beams of energies 0.6-3 MeV.The deuteron beam is delivered from a 4-MeV electrostatic accelerator and bombarded on a thick carbon target.The neutrons are detected at 0°,24°,and 48°and the protons at135°in the laboratory frame.Further,the ratio of the neutron yield to the proton yield was calculated.This can be used to effectively recognize the resonances.The resonances are found at 1.4 MeV,1.7 MeV,and 2.5 MeV in the12C(d,p)13C reaction,and at 1.6 MeV and 2.7 MeV in the12C(d,n)13N reaction.The proposed method provides a way to reduce systematic uncertainty and helps confirm more resonances in compound nuclei.

Simulation of proton–neutron collisions in inverse kinematics and its possible application

Neutrons have played a vital role in many nuclear physics fields.In some cases,the inverse kinematics of neutrons colliding with other nuclei are also worth studying.In this study,the inverse kinematics of thermal neutrons colliding with high-energy protons is simulated by using the Monte Carlo method.Thermal neutrons are taken as target particles,whereas protons are incident particles.The simulation implies that,after collision,the energy of the output neutron at 0°equals the energy of the incident proton.A possible application of the result is proposed that might yield single-energy neutrons.Some key parameters of the conceptual design were evaluated,demonstrating that the design may reach high-neutron-energy resolution.

Structure of the Quarks and a New Model of Protons and Neutrons: Answer to Some Open Questions

The described structural model tries to answer some open questions such as: Why do quarks not exist in the open state? Where are the antiparticles from the Big Bang?

Calculation of Neutron-Proton Mass Difference by the Monte Carlo Method

Calculation results of the Monte Carlo method of the average energy of the electrostatic interaction between the quarks are presented to the neutron and proton. The proposed model of the distribution of quarks in protons and neutrons is possible to assess the area which included a strong (gluon) interaction. Given the fact that the probability of finding a quark in the field with strong interaction is less than one, there is a good agreement between the experimental and calculated values of the mass difference between the neutron and the proton.

Predicting the Neutron and Proton Masses Based on Baryons which Are Yang-Mills Magnetic Monopoles and Koide Mass Triplets

We show how the Koide relationships and associated triplet mass matrices can be generalized to derive the observed sum of the free neutron and proton rest masses in terms of the up and down current quark masses and the Fermi vev to six parts in 10,000. This sum can then be solved for the separate neutron and proton masses using the neutron minus proton mass difference derived by the author in a recent, separate paper. The oppositely-signed charges of the up and down quarks are responsible for the appearance of a complex phase exp(iδ) and real rotation angle θ which leads on an independent basis to mass and mixing matrices similar to that of Cabibbo, Kobayashi and Maskawa (CKM). These can then be used to specify the neutron and proton mass relationships to unlimited accuracy using θ as a nucleon fitting angle deduced from empirical data. This fitting angle is then shown to be related to an invariant of the CKM mixing angles within experimental errors. Also developed is a master mass and mixing matrix which may help to interconnect all baryon and quark masses and mixing angles. The Koide generalizations developed here enable these neutron and proton mass relationships to be given a Lagrangian formulation based on neutron and proton field strength tensors that contain vacuum-amplified and current quark wavefunctions and masses. In the course of development, we also uncover new Koide relationships for the neutrinos, the up quarks, and the down quarks.

The Role of the Neutron-proton Interaction in Anomalous Band Crossing of Rare Earth Nuclei

Experimental estimate values of the n-p interaction between the odd protonand the aligning neutron pairs for odd proton nuclei in the first band crossing region areextracted based on the experimental quasi-particle routhians.The reliability of thismethod and the relation between the anomalous band crossing and the neutron-protoninteraction are discussed.

Solution of the Nucleon Structure Problem from a Field Theory of Fermions and Bosons and the Origin of the Proton Stability

A bound state formalism derived from a fermion-boson symmetric Lagrangian has been used to calculate the nucleon masses, the charge neutrality of the neutron, the magnetic moments and the electromagnetic form factor ratios μpGEp/GMpand μnGEn/GMn. A quantitative description is obtained, assuming a mixing of a scalar bound state of 3(f f¯)fstructure with its corresponding vector (f f¯)fstate (f indicating massless elementary fermions). Only a few parameters are needed, mainly fixed by energy and momentum conservation. The nucleon stability is explained by an extra binding in the confinement potential, negative for electric and positive for magnetic binding of the proton, and opposite for the neutron. The stronger electric extra binding of the proton allows a decay of the neutron to proton and electron.

Investigation of enhancement in planar fast neutron detector efficiency with stacked structure using Geant4

Geant4 based Monte Carlo study has been carried out to assess the improvement in efficiency of the planar structure of Silicon Carbide(SiC)-based semiconductor fast neutron detector with the stacked structure. A proton recoil detector was simulated, which consists of hydrogenous converter, i.e., high-density polyethylene(HDPE) for generating recoil protons by means of neutron elastic scattering(n, p) reaction and semiconductor material SiC, for generating a detectable electrical signal upon transport of recoil protons through it. SiC is considered in order to overcome the various factors associated with conventional Si-based devices such as operability in a harsh radiation environment, as often encountered in nuclear facilities. Converter layer thickness is optimized by considering 10~9 neutron events of different monoenergetic neutron sources as well as ^(241)Am-Be neutron spectrum. It is found that the optimized thickness for neutron energy range of 1–10 MeV is ~400 μm. However, the efficiency of fast neutron detection is estimated to be only 0.112%,which is considered very low for meaningful and reliable detection of neutrons. To overcome this problem, a stacked juxtaposition of converter layer between SiC layers has been analyzed in order to achieve high efficiency. It is noted that a tenfold efficiency improvement has been obtained—1.04% for 10 layers stacked configuration vis-à-vis 0.112% of single converter layer detector. Further simulation of the stacked detector with respect to variable converter thickness has been performed to achieve the efficiency as high as ~3.85% with up to 50 stacks.

STUDY ON OCCURENCE FORM OF PLATINUM IN XINJIE Cu－Pt DEPOSIT BY NAA AND SCANNING PROTON MICROPROBE

A combination of NAA and micro-PIXE was used to study concentrations and distributions of platinum group elements (PGE) in ores from Xinjie Cu-Pt deposit.The NAA results of the bulk indicate that the ores belong to the enriched Pt-Pd type.The element concentration maps of scanning micro-PIXE for the ores show that the occurence form of Pt is independent arsenide minerals. No PGE were detected in chalcopyrite of Xinjie Cu-Pt deposit. These information are economically beneficial to the mineral smelting process.

Characteristics of Filtered Neutron Beam Energy Spectra at Dalat Reactor

Filtered neutron technique was applied for producing quasi-monoenergetic neutron beams of 24 keV, 54 keV, 133 keV and 148 keV at the horizontal neutron channel No. 4 of the Dalat Nuclear Research Reactor. The study on physical characteristics of these beam lines has been carried out for efficient applications in neutron capture experiments. The filtered neutron spectrum of each beam has been simulated by Monte-Carlo method and experimentally measured by a gas-filled protonrecoil spectrometer. The neutron fluxes of these filtered beams were measured by the activation technique with standard foils of 197Au, using a high efficient HPGe digital gamma-ray spectrometer.

Proton dynamics in phosphotungstic acid impregnated mesoporous silica proton exchange membrane materials

Phosphotungstic acid is an excellent proton conductor that can be incorporated into porous supports, and nanocomposite proton exchange membrane materials made from mesoporous silica impregnated with phosphotungstic acid have been suggested for use in fuels cells operating> 100 ℃. In this work, quasielastic neutron scattering was used to study proton self-diffusion in mesoporous disordered and P6 mm symmetry silica impregnated with two concentrations of phosphotungstic acid. Overall, the silica structure had a significantly greater effect on proton conduction and diffusion than phosphotungstic acid concentration, with higher proton conduction occurring for the P6 mm symmetry silica samples. Quasielastic neutron scattering revealed two populations of protons diffusing through each sample, and that proton conduction is limited by the slower of these populations, which diffuse via a jump-diffusion mechanism. Whilst the fundamental jump-diffusion mechanism by which these slower protons moved was found to be similar for both silica supports and phosphotungstic acid concentrations, the faster diffusion occurring in P6 mm structured silica arises from a lower residence time of protons moving between sites in the jump-diffusion model, suggesting a lower energy barrier.

The Effects of δ Meson on the Neutron Star Cooling

In the framework of the relativistic mean field theory, the isovector scalar interaction is considered by exchanging δ meson to study the influence of δ meson on the cooling properties of neutron star matter. The calculation results show that with the inclusion of δ meson, the neutrino emissivity of the direct Urca processes increases, and thus enhances the cooling of neutron star matter. When strong proton superfluidity is considered, the theoretical cooling curves agree with the observed thermal radiation for isolated neutron stars.

Re-visit N／Z Ratio of Free Nucleons from Collisions of Neutron-Rich Nuclei as a Probe of EoS of Asymmetric Nuclear Matter

The N/Z ratio of free nucleons from collisions of neutron-rich nuclei as a function of their momentum is studied by means of isospin-dependent Quantum Molecular Dynamics. We find that this ratio is not only sensitive to the form of the density dependence of the symmetry potential energy but also its strength determined by the symmetry energy coefficient. The uncertainties about the symmetry energy coefficient influence the accuracy of probing the density dependence of the symmetry energy by means of the N/Z ratio of free nucleons of neutron-rich nuclei.

Density Distribution of ~8B Deduced with Core Plus Valence Proton

A popular method to fit the experimental data of nuclear total reaction cros section is the Glauber model.It fits the experimental data at high energy very well,but has a big difference at ingermediate energy.We have added the coulomb correction and the finite range correction into the Glauber model and used 2-parameter Fermi density distribution:

中国散裂中子源伴生质子辐照实验平台及其技术参数的确定

为了利用负氢离子加速器中伴随产生的质子成分,中国散裂中子源(China Spallation Neutron Source,CSNS)在直线加速器末端建设了伴生质子辐照实验平台(associated protons experimental platform,APEP)。为了确定其性能参数,采用散射测量、束斑照相、同位素活化法等实验方法对伴生质子辐照实验平台的主要参数进行了刻度。实验证实,该辐照平台可以提供的质子能量范围为10~80 MeV,束斑分布均匀,束流强度范围为1.2×10^(7)~4.0×10^(9) cm^(-2)·s^(-1)。伴生质子辐照实验平台运行稳定,每年提供超过5000 h的束流时间,可以满足宇航器件可靠性测试、探测器刻度、辐照育种以及材料抗辐照特性测试等多种应用需求。

基于瞬发伽马谱学的元素重建算法

质子治疗中的瞬发伽马射线是质子和靶标之间核反应的产物,瞬发伽马射线的特征能量和强度可以用来确定靶中元素的种类和数量,在之前的实验中已经证明,无论反应截面多么复杂,一旦确定了被照射元素和入射质子的能量,元素浓度与伽马射线光子数之间就存在一定的线性关系。然而,这种线性关系很难应用于医学成像,而且氢的非线性行为迄今尚未研究。将这种线性关系推广到包括氢等非线性情况的混合元素材料,并提出了一种通用的数学形式,即基于瞬发伽马谱学的重建算法(PGSRA)。PGSRA的基本假设是样品材料的PGS与元素的每摩尔伽马射线有某种关系。对于碳和氧,这种关系是线性的,而对于氢,这种关系是非线性的。由于2.23 MeV的伽马线来源于中子吸收辐射,研究氢非线性行为,利用蒙特卡罗模拟验证碳、氧和氢的不同组合,如聚甲基丙烯酸甲酯(PMMA)、戊二醇和乙醇二醇的线性和非线性关系。所有样品材料的碳、氧相对误差均小于4%。基于氢的非线性特性,其相对误差约为10%。此外,样品密度的相对误差对所有样品材料都小于3.5%。开发的PGSRA法可能是PGS和医学成像之间的第一座桥梁。