Nuclear Reactions

The elliptical flow of fragments is studied for different systems at incident energies between 50 and 1000 MeV/nucleon using Isospin-dependent Quantum Molecular Dynamics (IQMD) Model. Our findings reveal that elliptical flow shows a transition from positive (in-plane) to negative (out-of-plane) value in the mid-rapidity region at certain incident energy, known as transition energy. This transition energy is found to depend on the model ingredients, size of the fragments, composite mass of the reacting system as well as on the impact parameter of the reaction. A reasonable agreement is observed for the excitation function of elliptical flow between the data and our calculations. Interestingly, the transition energy is found to exhibit a power law mass dependence.

Performing experiments with transactinide elements demands highly sensitive detection methods due to the extremely low production rates (one-atom-at-a-time conditions). Preseparation with a physical recoil separator is a powerful method to significantly reduce the background in experiments with sufficiently long-lived isotopes (t 1/2 Z 0.5 s). In the last years, the new gas-filled TransActinide Separator and Chemistry Apparatus (TASCA) was installed and successfully commissioned at GSI. Here, we report on the design and performance of a Recoil Transfer Chamber (RTC) for TASCA-an interface to connect various chemistry and counting setups with the separator. Nuclear reaction products recoiling out of the target are separated according to their magnetic rigidity within TASCA, and the wanted products are guided to the focal plane of TASCA. In the focal plane, they pass a thin Mylar window that separates the $ 1 mbar atmosphere in TASCA from the RTC kept at $ 1 bar. The ions are stopped in the RTC and transported by a continuous gas flow from the RTC to the ancillary setup. In this paper, we report on measurements of the transportation yields under various conditions and on the first chemistry experiments at TASCA-an electrochemistry experiment with osmium and an ion exchange experiment with the transactinide element rutherfordium.

New models of thermally pulsing asymptotic giant branch (TP-AGB) stars of low mass and solar chemical composition are presented, namely, Z \ 0.02, and Y \ 0.28. The inÑuence of 1 ¹ M/M _ ¹ 3, various parameters (such as the initial core mass, the envelope mass, the mass-loss rate, the opacity, and the mixing length) on the properties of the models is discussed in detail. Our main Ðndings are the following :

McGNASH is a modern statitistical/preequilibrium nuclear reaction code, being developed at Los Alamos, which can simulate neutron-, proton-and photon-induced reactions in the energy range from a few-keV to about 150 MeV. It is written in modern Fortran 95 scientific language, offering new capabilities both for the developer and the user. McGNASH is still in a development stage, and a first public release is planned for later in 2005.

A brief review of antiproton--nucleus physics is presented. Some topics are related to early LEAR experiments, and others to more recent measurements or proposals. These include: exotic molecules, elastic and inelastic scattering, deep annihilation, strangeness production, neutron--antineutron oscillations, halo nuclei, antiproton production in nuclear reactions etc.

We have measured fission fragment-mass yields for neutron-induced fission of 232 Th and 238 U at energies 32.8, 45.3, and 59.9 MeV. The experiments were done at quasimonoenergetic neutron beams of the Cyclotron Research Center at Louvain-la-Neuve. To detect the fission fragments, a multisection Frisch-gridded ionization chamber was used. The measurement and data analysis techniques are discussed in detail. The obtained mass yields are compared to model calculations with the intermediate-energy nuclear reaction code MCFX. The MCFX code is used to calculate the fraction of fissioning nuclei after cascade, preequilibrium, and statistical reaction stages. The formation of mass distributions is considered as a result of oscillations of the mass-asymmetry degree of freedom in the potential well calculated with the temperature-dependent shell correction method. The experimental results as well as the results of the model calculations demonstrate that the probability of symmetric fission increases with incident neutron energy for both nuclei. The comparison also shows that the symmetric fission is more enhanced for thorium than for uranium with increasing neutron energy. We also compare 238 U results with available experimental data; the 232 Th data were measured for the first time.

Excitation functions have been measured for a number of proton-induced nuclear reactions on natural zinc in the energy range from 27.5MeV down to their threshold energy, using the activation method on stacked foils. Excitation functions and thick target yield for the reactions leading to the formation of 67Ga,66Ga,68Ga,62Zn and 65Zn are presented and compared with earlier reported experimental data. The

A new physical method of analysis of samples containing small quantities of aluminium is described. The sample is bombarded with fast protons and the resulting 7;-rays are analysed by the Ge(Li) technique. The high selectivity of these detectors allows identification of the nuclei responsible for the ;;-ray emission. A careful analysis has been made of the different nuclear reactions involved in the production of).-rays in the bombardment of aluminium. Four y-rays have been observed with sufficient intensities for rapid determination: 843 keV, 1 013 keV, 1 368 keV and 1 778 keV. Thick-target excitation yields are presented and discussed in view of their use in analysis. A complete tabulation of these reactions is also presented. The method allows the determination of the aluminium concentration in every solid matrix in the 100 ppm range. In some cases concentrations as low as I0 ppm can be observed. All these determinations are quantitative. Lower concentrations can be detected qualitatively. Examples of the application of the method to different substances are the following: stainless steel, inorganic compounds, crystals, evaporated layers, etc. The resonance pattern observed in the intensity curves can be used to measure the homogeneity and the thickness of thin layers containing aluminium (0.2 to 4/xm). In most cases the method can be considered non-destructive and there is no residual radioactivity. Analysis of a sample of a total weight not exceeding 0.1 mg can be achieved.

A new physical method of analysis of samples containing small quantities of aluminium is described. The sample is bombarded with fast protons and the resulting 7;-rays are analysed by the Ge(Li) technique. The high selectivity of these detectors allows identification of the nuclei responsible for the ;;-ray emission. A careful analysis has been made of the different nuclear reactions involved in the production of).-rays in the bombardment of aluminium. Four y-rays have been observed with sufficient intensities for rapid determination: 843 keV, 1 013 keV, 1 368 keV and 1 778 keV. Thick-target excitation yields are presented and discussed in view of their use in analysis. A complete tabulation of these reactions is also presented. The method allows the determination of the aluminium concentration in every solid matrix in the 100 ppm range. In some cases concentrations as low as I0 ppm can be observed. All these determinations are quantitative. Lower concentrations can be detected qualitatively. Examples of the application of the method to different substances are the following: stainless steel, inorganic compounds, crystals, evaporated layers, etc. The resonance pattern observed in the intensity curves can be used to measure the homogeneity and the thickness of thin layers containing aluminium (0.2 to 4/xm). In most cases the method can be considered non-destructive and there is no residual radioactivity. Analysis of a sample of a total weight not exceeding 0.1 mg can be achieved.

We model the abundance gradients in the disk of the Milky Way for several chemical elements (O, Mg, Si, S, Ca, Sc, Ti, Co, V, Fe, Ni, Zn, Cu, Mn, Cr, Ba, La and Eu), and compare our results with the most recent and homogeneous observational data. We adopt a chemical evolution model able to well reproduce the main properties of the solar vicinity. We compute, for the first time, the abundance gradients for all the above mentioned elements in the galactocentric distance range 4 - 22 kpc. The comparison with the observed data on Cepheids in the galactocentric distance range 5-17 kpc gives a very good agreement for many of the studied elements. In addition, we fit very well the data for the evolution of Lanthanum in the solar vicinity for which we present results here for the first time. We explore, also for the first time, the behaviour of the abundance gradients at large galactocentric distances by comparing our results with data relative to distant open clusters and red giants and select the best chemical evolution model model on the basis of that. We find a very good fit to the observed abundance gradients, as traced by Cepheids, for most of the elements, thus confirming the validity of the inside-out scenario for the formation of the Milky Way disk as well as the adopted nucleosynthesis prescriptions.

Mather type plasma focus with the bank energy, 150 kJ (30 kV, 333 lF), was studied for the induced activity of 18 F, a short-lived radioisotopes which is a b ? emitter with 511 keV of gamma rays and has a half-life t 1/2 = 110 min, through 16 O( 3 He,p) 18 F and 20 Ne(d,a) 18 F nuclear reactions. The results of simulated numerical computations show that activities of 3.786 9 10 10 Bq and 6.632 9 10 10 Bq were found for 16 O( 3 He,p) 18 F and 20 Ne(d,a) 18 F reactions, respectively. The calculations were carried out for the same initial and final energies conditions, when Plasma focus works with 150 kJ at the repetition rate of 1 Hz and for 120 min of running time. According to the simulated results, the activity of 20 Ne(d,a) 18 F had an increase because the projectile ion mass ''deuteron'' was lighter than the 3 He which resulted in the higher induced voltage and the number of projectile ions.

The fusion excitation functions for the 46Ti+64Ni, 5°Ti+~Ni and 19F+93Nb systems have been measured from ~ 10% below to 15% above the nominal Coulomb barrier, utilizing the recoil mass separator, HIRA at the Nuclear Science Centre, New Delhi. Mean spins have been deduced from the fusion cross sections by two different methods, one using the statistical model and the second by a fit to the fusion cross sections. Good agreement is found between them. It is seen that the simplified coupled-channel calculations, with couplings to the lowest surface inelastic excitations alone, do not explain both the observed fusion cross sections and mean spins in the low energy domain for all the three systems. A systematic comparison is made between the systems 46Ti+64Ni and 5°Ti+6°Ni which have quite different ground-state transfer Q-values (Qgg) for the transfer channels. The 46Ti+64Ni system shows a significant enhancement of the sub-barrier fusion cross section and mean spin as compared with the 5°Ti+~°Ni system, indicating the importance of the transfer channel coupling. Fusion cross section and mean spin have been studied for the near and sub-barrier fusion of the highly mass asymmetric system 19Fq-93Nb and compared with those for the 4STi+64Ni system leading to the same compound nucleus via the nearly symmetric entrance channel. Since the 19Fd-93Nb system has a large positive Q8g for one-proton pick-up, the fusion data have been complemented by one-nucleon transfer measurements at energies around the Coulomb barrier. A simultaneous analysis of the fusion excitation functions and mean spin data indicates no significant effects that may be related to the entrance channel mass asymmetry. PACS: 25.70.Jj, 24.10.Eq, 24.60.Dr. Keywords: NUCLEAR REACTIONS 64Ni(46Ti,X), EC.M. = 72.7-92.3 MeV; 6°Ni(5°Ti,X), EC.M. = 72.6-90.8 MeV; 93Nb(]9EX), EC.M. = 44.4-59.4 MeV; measured o'(evaporation residue), tr(E). 93Nb( 19F, X) transfer reaction, ELab = 57, 60 MeV. Self-supporting foils, recoil mass separator, multi-wire proportional counter. 0375-9474/96/$15.00 (~) 1996 Elsevier Science B.V. All rights reserved PII S0375-9474(96)001 10-8 N.

We present a detailed study of s-process nucleosynthesis in massive stars of solar-like initial composition and masses 15, 20, 25, and 30 M⊙. We update our previous results of s-process nucleosynthesis during the core He-burning of these stars and then focus on an analysis of the s-process under the physical conditions encountered during the shell-carbon burning. We show that the recent compilation of the 22 Ne(α, n) 25 Mg rate leads to a remarkable reduction of the efficiency of the s-process during core He-burning. In particular, this rate leads to the lowest overproduction factor of 80 Kr found to date during core He-burning in massive stars. The s-process yields resulting from shell carbon burning turn out to be very sensitive to the structural evolution of the carbon shell. This structure is influenced by the mass fraction of 12 C attained at the end of core helium burning, which in turn is mainly determined by the 12 C(α, γ) 16 O reaction. The still present uncertainty in the ...

Elastic, inelastic, one-, two-, three-and four-nucleon transfer reactions induced by 16, 18 0 and 12C bombardment of target A = 40-96 nuclei have been studied at incident energies well above the Coulomb barrier. The inelastic angular distributions show structure correlated to that of the elastic scattering, while the transfer-reaction angular distributions are structureless. The transfer reactions, however, are found to selectively populate states in the final nucleus. A strong Q-value dependence is observed for all of the reactions studied. This dependence and the angular distributions have been interpreted using classical and quantum mechanical (DWBA) models. E NUCLEAR REACTIONS *°'*aCa, 5°Ti, SZCr, 54Fe, sa'6°'62"64Ni, 86'88Sr, 9°'92'94"'96Zr,

Single-event upsets (SEU) in microelectronics are calculated from newly-developed silicon nuclear reaction recoil data for incident protons and neutrons with energies up to 150 MeV. This paper focusses on the nuclear reaction physics that is important for calculating recoil spectra, and burst generation rate spectra. Comparisons are made with previous results, obtained from intranuclear cascade calculations as well as from previous ENDF data below 20 MeV, to demonstrate new features in the present calculations. Calculated SEU cross sections are compared with measured data.

When sunlight is scattered by raindrops, why is it that colorful arcs appear in certain regions of the sky? Answering this subtle question has required all the resources of mathematical physics DOUBLE RAINBOW was photographed at Johnstone Strait in British Columbia. The bright, inner band is the primary bow; it is separated from the fainter secondary bow by a region, called Alexander'S dark band, that is noticeably darker than the surrounding sky.

The Vulcan Nd : glass laser at the Central Laser Facility is a Petawatt (10 15 W) interaction facility available to the UK and international user community. The facility came online to users in 2002 and considerable experience has been gained operating the Vulcan facility in this mode. The facility is designed to deliver irradiance on target of 10 21 W cm −2 for a wide-ranging experimental programme in fundamental physics and advanced applications. This includes the interaction of super-high-intensity light with matter, fast ignition fusion research, photon induced nuclear reactions, electron and ion acceleration by light waves and the exploration of the exotic world of plasma physics dominated by relativity.

The studies performed in the frame of a project destined for the search of new (t,n) and (p,n) reactions of interest in nuclear reactors are described. Experimental evidences of the observations of the reactions: 46 Ti(t,n) 48 V, 48 Ti(p,n) 48 V, 52 Cr(t,n) 54 Mn, 56 Fe(p,n) 56 Co, 72 Ge(t,n) 74 As and 74 Ge(p,n) 74 As, are presented. Additional data on some secondary reactions, already characterised for the production of 7 Be, 56 Co, 58 Co, 65 Zn and 88 Y, were also obtained. The significance of these data is discussed.

In this paper are presented the production methods for very "high specific activity" radionuclides (HSARNs) of vanadium (V), manganese (Mn) and thallium (Tl), which have been developed in our laboratories for labeling different chemical forms of these elements present in the echo-systems in ultra-trace amounts, for metallo-toxicological and bio-kinetic studies. Use was made of both cyclotron and thermal nuclear reactor. If the nuclear reaction and/or decay product has atomic number different from irradiated target, it is possible separating the radioactive nuclide from irradiated target, without intentional addition of isotopic carrier. These kinds of radionuclides are named No Carrier Added, NCA, and their specific activity is very high and can reach values close to the theoretical Carrier Free one, CF. The experimental determination of specific activity, chemical and radiochemical purities is mandatory for all these kinds of applications.

The lectures consider nonrelativistic and relativistic formalism in inelastic proton scattering; interaction of nucleons in free space; application of nucleon interaction formalism to the process of their scattering from nuclei; the method of coupled channels; relations between the formalism of the Schrödinger and Dirac equations; transformation of the relativistic equation into the “Schrödinger equivalent”; comparison of analytical approaches in the relativistic conception of inelastic proton scattering; the deformation model in the distorted-wave method based on relativistic and nonrelativistic formalisms; the optical model of the nucleus; application of various elements of the above discussed formalism to the analysis of experimental data on inelastic proton scattering.
With all the approaches, special attention is paid to the spin-orbit interaction and its origin,

High-spin states in the neutron-deficient 140 Gd nucleus have been studied with the 92 Mo( 54 Fe,α2p) reaction at a beam energy of 240 MeV. The level scheme of 140 Gd was considerably extended from what was previously known. In this work we concentrate on one of the 9 bands observed, which presents relatively strong M1 transitions and negligible signature splitting, and has an isomeric band-head, indicating a strongly coupled or high-K configuration. We compare this band to the K π = 8 − bands observed in N=74 isotones and propose a similar configuration assignment, but with a somewhat larger deformation.

To investigate the importance of three-nucleon forces (3NF) systematically over a broad range of intermediate energies, the differential cross sections of elastic proton-deuteron scattering have been measured at proton bombarding energies of 108, 120, 135, 150, 170, and 190 MeV at c.m. angles between 30°and 170°. Comparisons with Faddeev calculations show unambiguously the shortcomings of calculations employing only two-body forces and the necessity of including 3NF. They also show the limitations of the latest few-nucleon calculations at backward angles, especially at higher beam energies. Some of these discrepancies could be partially due to relativistic effects. Data at lowest energy are also compared with a recent calculation based on PT.

In-flight separation of unretarded nuclear reaction products has made considerable progress in recent years. Electromagnetic separators for exotic species produced by nuclearfission, heavy ion fusion, target spallation, or projectile fragmentation have been developed to separate isotopes over the whole periodic table of elements with energies up to the GeV/u range. Recently, the possibility to produce exotic nuclear beams with energies far above the Coulomb barrier by projectile fragmentation opened a new field of secondary beam physics, the direct use of isotopically separated beams of unstable nuclei for nuclear reactions. Characteristic examples of in-flight separation will be discussed with emphasis on the new generation of projectile fragment separators, including the future applicationof cooled and stored secondary beams for the application in nuclear physics.

For a few years at FLNP, JINR Dubna has already started new prospects for the development of new neutrons facilities that will replace the IBR-2 neutron pulsed research reactor, which will finish its activities in 2032 year. Some of the agreed projects are using fission process induced
by neutrons on neptunium based fuels. In the present research the neutron fission process on 237Np nucleus was investigated. Various parameters during the neutron induced fission of 237Np nucleus such as; fission cross-section, mass distributions, prompt neutrons emissions, isotopes production and neutrons spectra, were analyzed. The evaluations of the above observables were done by using TALYS – 9.1 software for incident neutron energy ranging from 0.4 MeV up to 25 MeV. The exact value of cross-section was measured as 5 – 5.5 MeV
in the present work, whereas from literature, it was found up to 10 MeV. For neutrons spectra, a separation of the contribution of different nuclear reaction mechanisms was obtained. Some important yields and cross-section production of isotopes have been recorded and were found within good agreement with literature data.

Quantum Chromodynamics, the microscopic theory of strong interactions, has not yet been applied to the calculation of nuclear wave functions. However, it certainly provokes a number of specific questions and suggests the existence of novel phenomena in nuclear physics which are not part of the the traditional framework of the meson-nucleon description of nuclei. Many of these phenomena are related to high nuclear densities and the role of color in nucleonic interactions. Quantum fluctuations in the spatial separation between nucleons may lead to local high density configurations of cold nuclear matter in nuclei, up to four times larger than typical nuclear densities. We argue here that experiments utilizing the higher energies available upon completion of the Jefferson Laboratory energy upgrade will be able to probe the quark-gluon structure of such high density configurations and therefore elucidate the fundamental nature of nuclear matter. We review three key experimental programs: quasi-elastic electro-disintegration of light nuclei, deep inelastic scattering from nuclei at x > 1, and the measurement of tagged structure functions. These interrelated programs are all aimed at the exploration of the quark structure of high density nuclear configurations.

This paper shows that the plane wave expansion can be a useful tool in obtaining analytical solutions to infinite integrals over spherical Bessel functions and the derivation of identites for these functions. The integrals are often used in nuclear scattering calculations, where an analytical result can provide an insight into the reaction mechanism. A technique is developed whereby an integral over several special functions which cannot be found in any standard integral table can be broken down into integrals that have existing analytical solutions

We have measured angular distributions of the 2H(SLi, 7Li)3H and 2H(SLi, 9Be)n reactions at E .... = 1.5 to 2.8 MeV using an 8Li-radioactive-beam technique. Astrophysical S-factors and reaction rates were calculated from the measured cross sections. Although the 2H(SLi, 9Be)n cross section is small, it can contribute to 9Be synthesis. The 2H(SLi, 7Li)3H reaction has a sufficiently large cross section to destroy SLi, which may decrease the synthesis of heavier elements. No products from the 2H(SLi, 9Li)p reaction were detected. We also present the results of calculations using the inhomogeneous model of primordial nucleosynthesis in several regions of parameter space.

We present an accurate ab initio method of calculating isotope shifts and relativistic shifts in atomic spectra. We test the method on neutral carbon and three carbon ions. The relativistic shift of carbon lines may allow them to be included in analyses of quasar absorption spectra that seek to measure possible variations in the fine structure constant ␣ over the lifetime of the Universe. Carbon isotope shifts can be used to measure isotope abundances in gas clouds: isotope abundances are potentially an important source of systematic error in the ␣-variation studies. These abundances are also needed to study nuclear reactions in stars and supernovae, and test models of chemical evolution of the Universe.

The 22Ne(bLi, d) a-transfer reaction has been used to search for ol-unbound levels in ZhMg of importance for resonant cr-capture on 22Ne in stellar helium burning. To determine the resonance strengths of the observed states the 12Ne(a, n12"Mg reaction was investigated in the energy range between 600 and 900 keV. One resonance was identified and its strength determined. The astrophysical implications of the present results are discussed.

The Accelerator Driven Test Facility (ADTF) is being developed as a reactor concepts test bed for transmutation of nuclear waste. A 13.3 mA continuous-wave (CW) proton beam will be accelerated to 600 MeV and impinged on a spallation target. The subsequent neutron shower is used to create a nuclear reaction within a subcritical assembly of waste material that reduces the

While the way in which the State makes decisions regarding matters of public policy cannot be reduced to a simple universal explanation, it is, however, important to try to grasp why certain matters are of sufficient concern to be dealt with by the governmental apparatus. In an analysis of the more than 38-year history of the fully State-owned CAREM (Central Argentina de Elementos Modulares) nuclear power reactor, I use the advocacy coalition framework and the political contexts in which it advanced to examine the beliefs held by the actors that shaped the progress of the project throughout its chronology. Originally conceptualized in the 1970’s as part of a military program for naval propulsion, the reactor was presented as a civilian project in 1984 and went through ups and downs in its development until the 2006 Argentinian Nuclear Plan from which it derives its budget today. I argue that it was the dual-use possibility of nuclear technology (civilian and military) which allowed the project to advance through different regimes, democratic administrations and economic policies.

This diff erence is tra, ced back to the use of a strong p exchange in Ref. 1. It is then shown that NN interactions which are constrained to fit the NN phase shifts favor an effective weak p exchange which will. not give rise to spectacul. ar collective effects. The uniqueness of the pNN interaction as constrained by NN scattering data is further shown by comparing the tensor forces of various interactions. Again NN interactions (including the Reid soft core) which fit NN scattering give a unique prescription for momentum transfers up to 3 fm ', ruling out a pure m-exchange or (m+ strong p)-exchange tensor force.

A simple and inexpensive method has been developed for the separation of 99m Tc from 99 Mo produced from the neutron activation of 98 Mo by 98 Mo(n,γ) 99 Mo nuclear reaction. The recovery of 99m Tc was performed by solid-liquid extraction based on alumina column chromatography. The overall radiochemical yield for the complete separation of 99m Tc was 85-97% (n=5). The separated Na[ 99m Tc]TcO 4 was of high radionuclidic, radiochemical and chemical purities. The method can be adopted for routine processing and use of 99m Tc in radiopharmacy operations.