A silicon multiplicity detector system for an experiment on theinteraction of antiprotons with nuclei at BNL

A large-angle multiplicity detector (LAMD) system has been developed and used in the BNL experiment E854, relating to antiproton-nucleus interactions. The purpose of the BNL experiment E854 was to search for the predicted formation of hot hadronic matter by energetic antiproton absorption on a range of nuclei. This experiment probed the high-temperature-low-density region of the nuclear matter phase diagram. The LAMD system performed well with an energetic antiproton beam. Charged particle multiplicity distributions from p¯ annihilations were measured. The design and performance of the LAMD system are outlined     

Measurements of momentum correlation and interaction parameters between antiprotons

The two-particle momentum correlation is influenced by the nuclear force between two particles, which has been intensively studied for nucleons and nuclei, but not much for antinucleons or antinuclei. In this pro-ceeding, we present our STAR measurements on momen-tum correlation function of antiproton–antiproton and proton–proton in Au+Au collisions at -------sNN√ =200 GeV at the Relativistic Heavy Ion Collider. Attractive nuclear force between two antiprotons is demonstrated, and the strong interaction parameters (the scattering length and the effective range) are determined. This measurement serves as an additional verification of CPT symmetry. The present information on the strong force in the antiproton–antipro-ton system provides a fundamental ingredient towards understanding the structure of more sophisticated antinuclei.     

Nuclear dynamics induced by antiprotons

Reaction dynamics in collisions of antiprotons on nuclei is investigated within the Lanzhou quantum molecular dynamics model. The reaction channels of elastic scattering, annihilation, charge exchange and inelastic collisions of antiprotons on nucleons have been included in the model. Dynamics on particle production, in particular pions, kaons, antikaons and hyperons, is investigated in collisions of p on12 C,20Ne,40 Ca and181Ta from low to high incident momenta. It is found that the annihilations of p on nucleons are of importance to the dynamics of particle production in phase space. Hyperons are mainly produced via meson induced reactions on nucleons and strangeness exchange collisions, which lead to delayed emission in antiproton-nucleus collisions.     

High-energy physics

We give here a brief summary of the material presented at the Eighth International Conference on High-Energy Physics. At this conference there were discussions of the results of studies of the interactions of mesons, nucleons, and strange particles at high energies, and of the weak interactions between particles. There was emphasis on the advances achieved in the study of the weak interactions.     

氘核中子反应截面的法捷耶夫方程理论计算

中子引起的轻核反应是核数据研究的重要内容。当前我国核数据库中氘核中子反应截面的计算结果局限于采用s 波可分离势,且入射能量在20 MeV以下。需要发展三体核反应的法捷耶夫方程理论方法,采用超出s 波的核子 核子相互作用,从而对更高能量范围内氘核全套中子反应截面做出准确的描述。本文介绍了利用法捷耶夫方程计算n+d三核子反应体系的弹性散射微分截面、破裂反应、破裂反应出射中子和质子的双微分截面的理论框架及数值计算结果,同时计算了弹性散射总截面和破裂反应总截面的激发函数。计算结果与实验数据及CENDL 32、ENDF/B Ⅷ.0、JENDL 5、JEFF 33等数据库中的评价数据符合较好。     

Extension of a nuclear reaction calculation code CCONE toward higher incident energies — multiple preequilibrium emission,and spectrum in laboratory system

A nuclear reaction calculation code CCONE, which was developed for nuclear data evaluation for JENDL/AC-2008 and JENDL-4, has been upgraded to improve the prediction accuracy for calculated cross sections at nucleon incident energies higher than 20 MeV. Multiple particle emission, in which nucleons and complex particles up to α-particle are involved, from pre-equilibrium reaction process was implemented based on the sequential-decay calculations for all produced exciton states within the framework of the two-component exciton model. The effect of velocity-change of particle-emitting nuclei on the multiple emission in preequilibrium and compound processes, which was not included in the previous evaluations, was taken into account to obtain spectra in the laboratory system using an average velocity approximation for each composite/compound nucleus. Calculated nucleon emission spectra at nucleon incident energies from 20 to 200 MeV were compared with experimental and evaluated data for the proton- and neutron-induced reactions on ²⁷Al. The present results are in good agreement with experimental data. It was found that their predictions were better than those of JENDL/HE-2007 especially for low emission energies at high incident energies.     

Multi-scale modeling of irradiation effects in spallation neutron source materials

Changes in mechanical property of Ni under irradiation by 3 GeV protons were estimated by multi-scale modeling. The code consisted of four parts. The first part was based on the Particle and Heavy-Ion Transport code System (PHITS) code for nuclear reactions, and modeled the interactions between high energy protons and nuclei in the target. The second part covered atomic collisions by particles without nuclear reactions. Because the energy of the particles was high, subcascade analysis was employed. The direct formation of clusters and the number of mobile defects were estimated using molecular dynamics (MD) and kinetic Monte-Carlo (kMC) methods in each subcascade. The third part considered damage structural evolutions estimated by reaction kinetic analysis. The fourth part involved the estimation of mechanical property change using three-dimensional discrete dislocation dynamics (DDD). Using the above four part code, stress-strain curves for high energy proton irradiated Ni were obtained.     

Inelastic Scattering of 14MeV Neutrons by Medium Weight Nuclei

Continuous spectra of neutrons inelastically scattered from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge and As have been measured at an incident energy of 14 MeV with good statistics. Time-of-flight technique was used. In the analyses there were used three sets of inverse-reaction cross section σ_i: (1) calculated with Perey-Buck potential, (2) with Bjorklund-Fernbach potential and (3) cross section assumed to be constant. The inverse-reaction cross section does not affect appreciably the values of nuclear temperature or nuclear level density parameter for these nuclei except Ti, V and Cr. The nuclear temperature was found to be nearly constant in the mass number region of 48–75. The level density parameter as a function of mass number follows the general trend suggested by Newton. Newton's coefficient is found to be 0.092, in agreement with values obtained in other experiments. The total inelastic scattering cross sections are derived.     

Influence of Admixture Gas on the Enhancement of Neutron Production in Plasma Focus Devices

In this article, considering the most important interactions between the ionized admixture particles and the working plasma ones, we have analyzed the effect of added gas on the current and confinement time of the pinched plasma in plasma focus devices. Moreover, we demonstrate how heating and cooling the pinched plasma can be controlled by the increase and decrease on the percentage of the added particles and by this way the rise in the rate of D–D nuclear reactions is calculated.     

An intranuclear cascade model for inelastic scattering and breakup reactions involving deuterons and alpha particles

The intranuclear cascade model is extended to cluster-induced (deuteron and alpha particle) nuclear reactions involving inelastic scattering and breakup reactions. The proposed model explains the projectile breakup process by describing the projectile cluster as a superposition of several states. The incident cluster and the produced cluster are assumed to be collections of independent particles and may undergo nuclear interaction through nucleon–nucleon interaction with the target nucleus. Trajectory deflections for the projectile and ejecta are incorporated in the model to account for angular distributions. Calculations with the proposed model followed by the generalized evaporation model are performed for validation by comparing with experimental double-differential cross-section spectra produced by bombarding an ²⁷Al target separately with 80-MeV and 99.6-MeV deuterons and 140-MeV alpha particles. The calculation results show good agreement with experimental spectra.     

An effective method of damping particle oscillations in proton and antiproton storage rings

A method is proposed for the damping of synchrotron and betatron oscillations of heavy particles, which makes use of the sharp increase in the cross section for the interaction of these particles with electrons at small relative velocity. It is shown that it is possible by this method to compress strongly the proton and antiproton bunches in storage rings, and also to achieve multiple storage of these particles.Translated from Atomnaya Énergiya, Vol. 22, No. 5, pp. 346–348, May, 1967.     

Beyond fusion,annihilation reactions of confined hydrogen

Theoretical mechanisms showing how antineutrons can enter a region of confined hydrogen or deuterium and decay into antiprotons is given. An annihilation reaction of a proton and antiproton releases energy. This starts a series of deuterium fissions that increase the probability of annihilation reactions. The gamma rays produced lose momentum via radiation pressure vibrations of the surrounding confinement lattice. This constitutes a change of radiation energy to kinetic energy, exhibited as heating of the lattice material. A likely mechanism of mass changing to energy is the annihilation of large particles breaking into a multiplicity of repeated less energetic positron annihilations. The explanation given shows that it is possible in theory to utilize the tremendous energy available from annihilation reactions. The harnessing of this final frontier of energy and power could ultimately prove to be the most useful energy source, particularly for propulsion systems. The reaction cited may be the initial step in using the energy from annihilation reactions. Excess heat from a Pons — Fleischmann-type reaction can be accounted for as annihilation, not fusion.     

基于协变密度泛函理论的258Fm诱发裂变动力学研究

采用基于协变密度泛函理论的含时生成坐标方法研究了258Fm低能诱发裂变动力学性质,重点探讨了裂变位能曲面、裂变碎片总动能分布和碎片质量分布等。研究表明,258Fm位能曲面中存在显著的对称裂变谷,因而其低能裂变碎片总动能分布与质量分布均呈单峰结构,且随剪裂线判据Qn（脖子处粒子数）从4减至1,碎片总动能分布变窄,碎片质量分布的峰值从988%增至1028%。此外,随初态激发能从83 MeV增至173 MeV,碎片质量分布峰值从988%降至855%。     

Proton/antiproton collisions with positronium in the presence of an electric field

Effects of aligned electric field on the hydrogen formation mechanism have been studied. Classical trajectory Monte Carlo (CTMC) method is used to simulate the proton/antiproton collisions with positronium (Ps) in the energy range of 1-200 keV. Total cross section for an electron/positron capture by colliding proton/antiproton has been calculated using the simple Coulomb potential. The hydrogen and antihydrogen formation in these capture processes, as expected, is reported to be charge conjugate. The capture cross sections are in reasonable agreement with the recently reported experimental and theoretical results. The effects of the external electric field are seen to be quite prominent.     

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.     

Hadron Coolers at CERN

Two types of cooling (electronic and stochastic) are used in the AD (antiproton decelerator) for efficient deceleration and to provide the required parameters of the antiproton beam. In the not too distant future electronic cooling will be used in LEIR (low-energy ion ring) to accumulate ions in the LHC (large hadron collider). Both cooling systems are described.     

Model-based cross section calculations on production of ~(43,34)Sc,~(45)Ti,~(51)Cr,~(54)Mn,and ~(55)Fe radioisotopes

A cross section database on excitation functions of reactions produced by charged particles is essential for many areas of nuclear research. Particularly, accurate knowledge on nuclear cross sections for the cyclotron production of radioisotopes is very important for nuclear medicine. In the present paper, the cross section calculations for the production of~(43),~(34)Sc,~(45)Ti,~(51)Cr,~(54)Mn, and~(55) Fe radioisotopes were carried out by the use of ALICE/ASH code using the Fermi gas model, Kataria Ramamurthy Fermi gas model, and superfluid nuclear model for nuclear level density. Thereby, these model calculations were compared with the available measured data.     

Double excitation of helium in collisions with proton and antiproton impact in the energy range 50-500 keV

Double-electron excitation processes of helium atoms by proton and antiproton impact have been theoretically investigated using the four-body formalism of boundary corrected continuum intermediate state (BCCIS-4B) approximation in the energy range of 50-500 keV. In this formalism, the presence of the projectile in the exit channels is described by distorting the final bound state wave functions with coulomb waves (associated with the projectile-electron interactions). The results are in good agreement with the other theoretical and experimental results. Reasonably better agreements have been found in the intermediate and high energy regions. Contributions to the cross section of the different magnetic sub-shells are also analysed.     

High-energy nuclear physics and nuclear astrophysics at the Radium Institute

Research into high-energy nuclear physics and nuclear astrophysics at the Radium Institute is briefly reviewed. The history of cosmic-ray research is outlined, from the early years of the Institute, as well as the history of research on high-energy physics. The basic work on nuclear astrophysics, cosmochronology, and astrochemistry is described. Research at the Institute on direct nuclear reactions, nuclear fragmentation and multifragmentation, deeply inelastic nuclear processes, nuclear fission at high exciting energies, nuclide formation at the limit of stability, multiple particle formation in relativistic internuclear reactions, and other topics is considered. Scientific and methodological accomplishments are noted. V. G. Khlopin Radium Institute. Translated from Atomnaya énergiya, Vol. 86, No. 6, pp. 419–426, June, 1999.     

The antiproton depth-dose curve measured with alanine detectors

In this paper we report on the measurement of the antiproton depth-dose curve, with alanine detectors. The results are compared with simulations using the particle energy spectrum calculated by FLUKA, and using the track structure model of Hansen and Olsen for conversion of calculated dose into response. A good agreement is observed between the measured and calculated relative effectiveness although an underestimation of the measured values beyond the Bragg-peak remains unexplained. The model prediction of response of alanine towards heavy charged particles encourages future use of the alanine detectors for dosimetry of mixed radiation fields.